担当区分：最終著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Advances in Space Research  

This paper proposes a method to estimate two sets of orbital parameters (inclination, right ascension of the ascending node, and nodal precession rate) of the collided objects from in situ measurements of sub-millimeter-size debris, using the first-ever accidental collision between US Iridium 33 and Russian Cosmos 2251 as an example. This collision released a large number of fragmentation debris and have had a tremendous impact on the environment around the Earth. Objects larger than 10 cm are cataloged and tracked, but it is difficult to observe sub-millimeter-size debris from the ground and predict their orbits accurately. Thus, this fact leads to insufficiently modelled sub-millimeter-size debris, despite their potential to space mission termination. Therefore, in situ debris measurements are essential to protect space systems against sub-millimeter-size debris. Previous studies assumed that an in situ debris measurements satellite records the position at the time of impact with sub-millimeter-size debris, and then demonstrated that it is possible to estimate the orbital parameters from in situ debris measurements when a single object is broken up. However, when two objects collide, measurements come from both objects, so the previous method cannot be simply applied. Besides, the inclination of the broken-up objects to which the previous method can be applied is constrained by the inclination of the measurements satellite. To solve this problem, this paper proposes using azimuth at the time of impact and applying the Lomb-Scargle Periodogram, a kind of frequency analysis. Finally, this paper demonstrates that it is possible to identify accidental collisions in space through in situ measurements.

DOI： 10.1016/j.asr.2025.03.075

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Space Safety Engineering  

The rapid growth of resident space objects in Earth's orbit has intensified the need for advanced space situational awareness and space domain awareness to manage satellite traffic and prevent collisions. Attitude estimation is critical for accurate state propagation, as non-gravitational forces like solar radiation pressure and atmospheric drag depend on the object's attitude. This study explores using light curves, time variation of an object's brightness, to estimate a space object's attitude. Light curve inversion, traditionally used in astronomy, faces challenges when applied to resident space objects due to their non-convex shapes and specular reflections. Conventional methods for attitude estimation often assume known shape and surface parameters, which are usually unknown for space debris generated by a collision or breakup. To address this issue, this study proposes the estimation method combining Gaussian process regression with the unscented Kalman filter. This study uses Gaussian process regression for a non-parametric observation model, enhancing robustness against unknown surface parameters. Numerical examples consider a box-wing object in a geosynchronous orbit and demonstrate that the proposed method has better estimation accuracy than a conventional unscented Kalman filter. The numerical simulation results also represent the attitude estimation robust against uncertainties in surface properties, contributing to practical scenarios in space situational awareness and space domain awareness where the object parameters are unknown.

DOI： 10.1016/j.jsse.2025.02.008

Web of Science

Scopus

記述言語：英語   出版者・発行元：宇宙航空研究開発機構 (JAXA)  

In order to control the increase in space debris and to actively promote its removal, the activities of space companies are indispensable, and the incentive design for them needs to be properly implemented as a social system. However, under the fiat currency system, it has to rely on a design based on taxation and a system of subsidies, and there have been difficulties in obtaining a realistic solution. The authors have proposed a solution using a new digital currency (ADR currency) in the past, but there is another difficulty in that the concept is difficult to spread due to differences with the current monetary system. Therefore, in this study, a text-based game simulating the corporate activities of space companies in a society where legal tender and ADR currency coexist was developed as a serious game (a game whose main purpose is not entertainment) using generative AI. The method is simple and could be useful for simulating decision-making on various other issues related to space exploration.

DOI： 10.20637/0002001398

CiNii Research

記述言語：日本語   出版者・発行元：一般社団法人 日本航空宇宙学会  

<p>本稿では，宇宙エレベーターの建設費を10年で回収できると仮定し，宇宙デブリ衝突による宇宙エレベーターの破断を考慮して，10年後の宇宙エレベーターの残存率を評価した結果を示す．その結果，宇宙エレベーターがその建設費を回収できるまで残存するためには，宇宙デブリ衝突による宇宙エレベーターの損傷を最小化するような冗長系だけでなく，現在の衝突フラックスと比してほぼ0％にまで宇宙デブリ環境を改善しなければ実現不可能であることが分かった．</p>

DOI： 10.14822/kjsass.72.12_438

CiNii Research

掲載種別：研究論文（学術雑誌）   出版者・発行元：Acta Astronautica  

Laser ablation technology enables contactless debris removal, providing the advantages of safety and cost efficiency. To deorbit space debris using laser ablation, the attitude motion of the debris must be controlled in advance. Although a previous study derived an attitude control procedure, it empirically determines control gains and is easily affected by assumed preconditions. To solve this problem, this paper proposes an improved attitude control law using laser ablation. Previous methods use feedback control based on the angular velocity error and error quaternions to obtain a reference torque. By analogy with a magnetic attitude control law, this study designs a reference torque based on the angular momentum errors and presents theoretical condition for designing the control gains. Numerical examples using the proposed control law are conducted to control the target attitude from a random initial rotation of 1 rpm to an arbitrary attitude, which verify the effectiveness of the proposed method. Furthermore, the position, direction, and magnitude uncertainties of laser irradiation are introduced to numerically examine their effects on the control accuracy under environmental disturbances.

DOI： 10.1016/j.actaastro.2024.06.023

Scopus

researchmap

出版者・発行元：Acta Astronautica  

This paper discusses the processes which should be taken to establish debris indices that assess the orbital environmental impact of spacecraft or missions in orbit. The first process is establishing a methodology and criteria for evaluating an impact on the orbital environment. This study proposed an assessment method to evaluate the cumulative environmental changes during an evaluation period. It evaluated the impact of an uncontrolled LC mission abandoned in orbit. This study used Near-Earth Orbital Debris Environment Evolutionary Model (NEODEEM), an orbital environmental evolutionary model that Kyushu University and JAXA developed. The second process is the debris index formulation. This study considered four steps to establish the debris index. To reveal the establishing process of a debris index, this study used debris indexes as candidates which consider expected number of fragments generated from an object. The calculated debris index values were compared to the impact on the environment assessed by the evolutionary model to see if there was any correlation. Further, this study conducted numerical simulations of un-controlled large-constellation satellites abandoned in low earth orbit in different scenarios, and of active debris removals of large intact objects by NEODEEM. This paper discusses the applicability of proposed environmental assessment methods and the debris index.

DOI： 10.1016/j.actaastro.2024.06.047

Web of Science

Scopus

掲載種別：研究論文（学術雑誌）   出版者・発行元：Advances in Space Research  

This paper proposes the formation keeping control law for deorbiting debris by a laser ablation. Laser ablation is vital technology for contactless active debris removal, where a chaser satellite with a laser system irradiates laser pulses to a target object to generate the ablation force for deorbiting. The deorbiting force decelerates the target, and the chaser must maintain its relative position and continue irradiating. In other words, both the chaser and the target are supposed to be deorbited simultaneously, where both have accelerations. Although conventional formation flying missions assume that only a chaser maneuvers, the formation flying in this paper considers that both a chaser and a target have accelerations. Thus, this paper derives the relative equations of motion between the chaser and the target in powered flight and their analytical solution using relative orbital elements. A control law based on the analytical solution is proposed, which determines the timings and directions of the laser ablation and the electrical thrust so that the formation periodically returns to a desired formation. Numerical simulations first examine the control law in two cases with different maneuver timings. Then, a Monte Carlo simulation is performed to verify the effectiveness of the control law for a variety of desired formations.

DOI： 10.1016/j.asr.2024.05.029

Web of Science

Scopus

researchmap

出版者・発行元：Acta Astronautica  

This paper examines the effect of shortening the post-mission disposal (PMD) orbit lifetime (remaining orbit lifetime after PMD) from 25 years to 5 or 1 year. Using NEODEEM, the debris evolutionary model developed by Kyushu University and JAXA, the change in the orbital environment at various altitude bands for long-term stability and short-term safety are discussed. It was confirmed that the PMD compliance rate is more important than shortening the orbit lifetime for improving the long-term stability of the orbital environment. In the short term, the 5- or 1-year rule reduced the collision rate and collision avoidance frequency at an altitude below 700 km, more than the 25-year rule, thus shortening the PMD orbit lifetime improves short-term safety, especially at low altitudes. The paper also evaluates the effect of large constellations (LCs) and it was shown that shortening the PMD orbit lifetime of LCs improves short-term safety, but the long-term impact is dominated by the number of LCs that remain at high operational altitudes due to PMD failure. It shows that the post-mission disposal lifetime and required compliance rate should be set according to the number and size of objects expected to be launched in the future.

DOI： 10.1016/j.actaastro.2024.03.033

Web of Science

Scopus

記述言語：英語  

DOI： 10.1038/s42004-024-01116-3

Web of Science

PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Acta Astronautica  

This study introduces a new method to estimate the orbital parameters (inclination, nodal precession rate, and right ascension of the ascending node) of the broken-up object using in-situ debris measurements. To reduce collision probability with tiny debris generated from breakups of satellites, it is required to identify the origin of breakups and predict the orbit of debris. In general, small debris cannot be tracked from the ground, thus an in-situ measurement is an effective method to detect sub-millimeter-sized debris. Previous studies developed a method to identify the location of breakup origin from an in-situ measurement, however, it can be applied to an ideal situation where the detection occurs at the intersection of the orbit planes. This study introduces a new method to estimate the orbital parameters by fitting the model of geocentric declination to the measurement data. This method can be applied to practical situations that cannot be validated in previous studies. This paper also adopts iteratively reweighted least squares to improve estimation accuracy and mitigate initial value dependencies.

DOI： 10.1016/j.actaastro.2023.12.038

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrodynamics  

This paper answers how multiple satellites are seen from the ground. This question is inspired by space-advertising, a public exhibition in the night sky using a dot matrix of satellites that are bright enough to be seen by the naked eye. Thus, it is important for space advertisement that the specific dot matrix is seen. Moreover, the stability of the dot matrix during a visible span is very valuable. To stabilize the dot matrix, this study formulates an apparent position of a dot from a representative dot seen from the ground. The formulation, linear functions of a set of relative orbital elements, reveals the appearance of the dot matrix. The proposed relative variable in the formulation drives the instability of the dot matrix, thereby revealing an initial stable configuration of deputies from a chief. The arbitrary dot matrix designed using the configuration is stable even at low elevations without orbital control during the visible span.

DOI： 10.1007/s42064-023-0180-6

Web of Science

Scopus

掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Space Safety Engineering  

This paper proposes less fuel strategies for space debris removal. To mitigate the risk of space debris cost-efficiently, multi-rendezvous missions are under development. On the other hand, multi-rendezvous missions often require changing orbital planes of removal satellites, which requires a huge amount of ΔV. Therefore, this study focuses on exploiting the J2 perturbation force as an auxiliary force and aims to establish maneuver rules that minimize ΔV consumption while maximizing the benefit of the J2 perturbation. The J2 perturbation equation is explored analytically, which clarifies whether the change in the semi-major axis or the inclination dominates the efficiency of the exploitation. A straightforward criterion is extracted which determines the efficient maneuver based on the initial inclination of the satellite.

DOI： 10.1016/j.jsse.2024.08.002

Web of Science

Scopus

researchmap

記述言語：英語   出版者・発行元：宇宙技術および科学の国際シンポジウム  

<p>The effects of GTO debris to LEO environment are revealed using evolutionary model. GTO debris orbits are modeled as a reference of distribution of actual objects in GTO extracted from JAXA's initial population file. Firstly, three cases of simulation with different perigee altitude were shown taking into accounts the distribution of GTO debris. It indicated that the debris with perigee altitude of over 400 km have long term effects while the debris with perigee altitude of 200 km decay shortly. The effect of continuously generation of GTO debris was secondly investigated. Since the GTO debris has long term orbital life, the number of its debris would keep increasing and accumulate in orbit. Lastly, the risk of GTO debris considering the actual number of debris and future works were discussed.<b><i> </i></b></p>

DOI： 10.57350/jesa.110

CiNii Research

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 日本航空宇宙学会  

<p>This paper proposes an attitude estimation technique that focuses on rapid change in light intensity, called glint. The states of space objects, such as shape, attitude, and surface properties, are essential information for performing active debris removal and monitoring the operational states of the satellite. Light curve inversion is a cost-effective measure to inversely estimate dynamic states. However, the light curve inversion suffers from divergence when the initial estimate is far from the true state. The glint occurs when a specific geometrical constraint is satisfied, and this glint constraint can be exploited to correct the attitude estimate in a Kalman filter. Thus, assuming a target object as a flat plate, this paper examines whether glint can be used in attitude estimation to improve estimation accuracy. Numerical simulations verify that the attitude estimation filter successfully converges, even when the initial estimate contains a significant error.</p>

DOI： 10.2322/tastj.22.59

CiNii Research

researchmap

出版者・発行元：AIAA SciTech Forum and Exposition, 2024  

This paper proposes a close approach analysis method considering object attitude change. Implementing a detailed close approach analysis is important for space situational awareness. Conventional conjunction assessment methods assume the shape of the object as a encompassing sphere, which excludes considering the attitude change. However, most of the spacecraft are not spherical, and conventional methods result in overestimation. The proposed method in this paper consists of two steps: 1) calculation of the time of close approach with two objects as point masses and 2) interpolation of the first and last states in the time duration when the close distance is less than a given threshold. Dual quaternions are employed to express the translational and rotational motions, which ensures the uniqueness of the interpolation. Numerical simulations are performed to verify the proposed method and compare it with a conventional method.

DOI： 10.2514/6.2024-1632

Scopus

出版者・発行元：Journal of Space Safety Engineering  

This study evaluates the environmental impacts of orbital fragmentation such as an anti-satellite test, collision between two objects, and explosion. A debris environment evolutionary model named NEODEEM, jointly developed by Kyushu University and JAXA, is used to predict future populations and calculate collision probabilities after a fragmentation. This study focuses on characteristics of the fragmented objects, such as altitude, mass, and whether they belong to a Large Constellation (LC). When a fragmentation occurs at higher altitudes, the new fragments will remain in orbit for a long time. Due to this accumulation, the fragments will not only keep the number of objects and probability of collision higher but also cause the risk of secondary collisions between fragments and background objects. When a collision occurs inside an LC at a lower altitude, the impacts will be short-term because most of fragments decay quickly. However, the number of conjunctions, i.e., operational roads, will increase rapidly because many satellites are operated at the same altitude. This study also discusses a collision probability to an LC taking into account the small size of fragments larger than 1 cm.

DOI： 10.1016/j.jsse.2024.07.008

Web of Science

Scopus

掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Space Safety Engineering  

This study proposes a relative orbit control law for laser debris removal missions considering the uncertainties of laser ablation and atmospheric drag. A removal spacecraft irradiates laser pulses to a target debris to generate the ablation force for deorbiting. The deorbiting force lowers the target altitude, and the removal spacecraft must follow it to maintain its relative position for continuous laser irradiation. The difficulty stems from uncertainties of the magnitude of laser ablation and external disturbances such as atmospheric drag. To tackle this problem, this study derives an adaptive control method using the Gaussian process regression to cancel the uncertainties with a nonparametric regression model. Numerical simulations verify the proposed control law under the uncertainties of laser ablation and atmospheric drag. The proposed control law can contribute to the realization of a safer and more secure mission not only for laser debris removal missions, but also for other on-orbit services.

DOI： 10.1016/j.jsse.2024.04.007

Web of Science

Scopus

researchmap

Web of Science

記述言語：英語   出版者・発行元：宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)  

レポート番号: ASTRO-2023-C006(004)/In-person

CiNii Research

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Because of its large number of satellites, a large constellation (a LC) greatly affects other objects in LEO. Several studies reveal the impact of a LC in LEO missions in various operational scenarios. This study evaluated the environmental impact of a LC explosion in the short and long-term using the Near-Earth Orbital Debris Environment Evolutionary Model (NEODEEM). Although setting mission scenarios and analysis conditions is important in LC simulations, it is difficult to consider all operational scenarios due to the many combinations. Therefore, this study conducted impact assessments of explosions in a LC, concentrating on the number of explosions, orbital altitude, and scaling factor of the explosions. The results indicated that it is not enough for LC to comply with the current requirement of probability of accidental explosions which is less than 0.001 during the operation. This is because, if the rate is applied directly to a LC with thousands of satellites, continuous explosions (i.e., several satellites explode every year) will occur during the mission duration of LC. The paper also discusses the behavior of fragments from explosions at different altitudes. The explosions at low altitudes have no significant impact in the long term, although it can cause an incremental change in collision risk in the short term. Similarly, the explosions at high altitudes, such as 1,250 km, have only slightly increments of the expected number of collisions, but its impact could last for over 100 years. The probability of explosions of a LC must be carefully determined through a series of simulations based on the number of satellites and the operational orbit of a LC. This paper also discusses what should be considered in future LC design and operations regarding explosion prevention.

DOI： https://doi.org/10.1016/j.jsse.2023.03.007

出版者・発行元：Journal of Space Safety Engineering  

Because of its large number of satellites, a large constellation (a LC) greatly affects other objects in LEO. Several studies reveal the impact of a LC in LEO missions in various operational scenarios. This study evaluated the environmental impact of a LC explosion in the short and long-term using the Near-Earth Orbital Debris Environment Evolutionary Model (NEODEEM). Although setting mission scenarios and analysis conditions is important in LC simulations, it is difficult to consider all operational scenarios due to the many combinations. Therefore, this study conducted impact assessments of explosions in a LC, concentrating on the number of explosions, orbital altitude, and scaling factor of the explosions. The results indicated that it is not enough for LC to comply with the current requirement of probability of accidental explosions which is less than 0.001 during the operation. This is because, if the rate is applied directly to a LC with thousands of satellites, continuous explosions (i.e., several satellites explode every year) will occur during the mission duration of LC. The paper also discusses the behavior of fragments from explosions at different altitudes. The explosions at low altitudes have no significant impact in the long term, although it can cause an incremental change in collision risk in the short term. Similarly, the explosions at high altitudes, such as 1,250 km, have only slightly increments of the expected number of collisions, but its impact could last for over 100 years. The probability of explosions of a LC must be carefully determined through a series of simulations based on the number of satellites and the operational orbit of a LC. This paper also discusses what should be considered in future LC design and operations regarding explosion prevention.

DOI： 10.1016/j.jsse.2023.03.007

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： https://doi.org/10.2514/1.G005961

出版者・発行元：Proceedings of the International Astronautical Congress, IAC  

This paper examines the effect of shortening the post-mission disposal lifetime from 25 years to 5 or 1 year. Using NEODEEM, the debris evolutionary model developed by Kyushu University and JAXA, the change in the orbital environment at various altitude bands for long-term stability and short-term safety such as the number of collision avoidance maneuvers and collision rate are discussed. It was confirmed that the PMD compliance rate is more important than shortening the orbit lifetime for improving the long-term stability of the orbital environment. The collision rate below 700 km increased if the number of launches to high altitudes and the post-mission disposal (PMD) compliance rate increase, although the collision impact is not long-term. In the short term, the 5- or 1-year rule reduced the collision rate and collision avoidance frequency at an altitude around 600 km, more than the 25-year rule, thus shortening the PMD orbit lifetime improves short-term safety, especially at low altitudes. The paper also evaluates the effect of large constellations shows that the post-mission disposal lifetime and required compliance rate should be set according to the number and size of objects expected to be launched in the future.

Scopus

出版者・発行元：Proceedings of the International Astronautical Congress, IAC  

This paper discusses the processes which should be taken to establish debris indices that assess the orbital environmental impact of spacecraft or missions in orbit. The first process is establishing a methodology and criteria for evaluating an impact on the orbital environment. This study proposed an assessment method to evaluate the cumulative environmental changes during an evaluation period. It evaluated the impact of an uncontrolled LC mission abandoned in orbit This study used NEODEEM, an orbital environmental evolutionary model that Kyushu University and JAXA developed. The second process is the index formulation. This study considered four steps to establish the debris index, and proposed an index that could be evaluated by NEODEEM. The difference between the calculated index values and the environmental impact was also discussed. Further, this study conducted numerical simulations of un-controlled large-constellation satellites abandoned in low earth orbit in different scenarios, and of active debris removals of large intact objects by NEODEEM. This paper discusses the applicability of proposed environmental assessment methods and the debris index.

Scopus

出版者・発行元：Journal of Guidance, Control, and Dynamics  

DOI： 10.2514/1.G005961

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Remediation measures, such as Active Debris Removal (ADR) has been studied in order to preserve the space environment. Large derelict objects in crowded orbits are considered ADR targets because they are the source of numerous small debris in case of fragmentation. The target for removal must be chosen carefully because cost is the major issue in realizing ADR, and it is necessary to remediate the orbital environment as efficiently as possible. Last year, Dr. McKnight et al. presented the top 50 debris removal targets by combining each of the top 50 lists compiled by eleven international teams. This paper dis- cusses the considerations involved in selecting debris removal targets. This study first considered the top 50 objects, to be removed according to each index, and then evaluated the consequences of the removal using Near-Earth Orbit Debris Environment Evolutionary Model (NEODEEM), a debris evolutionary model developed by Kyushu University and JAXA. Differences in debris removal targets were studied for long-term stability or short-term safety. This paper discusses why some indices are effective in the short or long term in terms of the orbital distribution of selected targets and the effects of removal in each altitude band. It also discusses the differences between removing 50 objects and removing one object each year, and the effects of removal timing and so on. It found that integrating different indices is effective, and that the removal target must be determined according to the situation. It is more important to remove as much debris as possible as early as possible rather than focusing on an object’s ranking in a list.

DOI： https://doi.org/10.1016/j.jsse.2022.05.006

出版者・発行元：Journal of Space Safety Engineering  

Remediation measures, such as Active Debris Removal (ADR) has been studied in order to preserve the space environment. Large derelict objects in crowded orbits are considered ADR targets because they are the source of numerous small debris in case of fragmentation. The target for removal must be chosen carefully because cost is the major issue in realizing ADR, and it is necessary to remediate the orbital environment as efficiently as possible. Last year, Dr. McKnight et al. presented the top 50 debris removal targets by combining each of the top 50 lists compiled by eleven international teams. This paper discusses the considerations involved in selecting debris removal targets. This study first considered the top 50 objects, to be removed according to each index, and then evaluated the consequences of the removal using Near-Earth Orbit Debris Environment Evolutionary Model (NEODEEM), a debris evolutionary model developed by Kyushu University and JAXA. Differences in debris removal targets were studied for long-term stability or short-term safety. This paper discusses why some indices are effective in the short or long term in terms of the orbital distribution of selected targets and the effects of removal in each altitude band. It also discusses the differences between removing 50 objects and removing one object each year, and the effects of removal timing and so on. It found that integrating different indices is effective, and that the removal target must be determined according to the situation. It is more important to remove as much debris as possible as early as possible rather than focusing on an object's ranking in a list.

DOI： 10.1016/j.jsse.2022.05.006

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）  

An active debris removal method using a laser is a promising technology for its advantage in contactless operations. This paper deals with the attitude control of an uncooperative target by a laser, which is an important phase before deorbiting. The difficulty of attitude control by the laser stems from the torque directional constraint because the laser generates thrust along the normal vector of the irradiated face irrespective of the irradiating direction. Thus, the control torque along the normal vector cannot be generated, which makes the attitude control with the laser torque challenging. To tackle this problem, this paper first designs a reference controller that assumes arbitrary control torques are available. Then, a method for determining the irradiating point is proposed so that the difference between the reference torque and the actual one is minimized. Although the proposed controller does not guarantee theoretical convergence to the desired attitude, the effectiveness of the proposed controller is numerically verified for a box-type object. Furthermore, the robustness to the uncertainties of thrust magnitude and direction is also examined by Monte Carlo simulations.

DOI： https://doi.org/10.1016/j.actaastro.2022.04.024

記述言語：英語   出版者・発行元：Acta Astronautica  

An active debris removal method using a laser is a promising technology for its advantage in contactless operations. This paper deals with the attitude control of an uncooperative target by a laser, which is an important phase before deorbiting. The difficulty of attitude control by the laser stems from the torque directional constraint because the laser generates thrust along the normal vector of the irradiated face irrespective of the irradiating direction. Thus, the control torque along the normal vector cannot be generated, which makes the attitude control with the laser torque challenging. To tackle this problem, this paper first designs a reference controller that assumes arbitrary control torques are available. Then, a method for determining the irradiating point is proposed so that the difference between the reference torque and the actual one is minimized. Although the proposed controller does not guarantee theoretical convergence to the desired attitude, the effectiveness of the proposed controller is numerically verified for a box-type object. Furthermore, the robustness to the uncertainties of thrust magnitude and direction is also examined by Monte Carlo simulations.

DOI： 10.1016/j.actaastro.2022.04.024

Web of Science

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper briefly introduces a new approach to estimate some orbital parameters of on-orbit satellite fragmentations (specifically, the direction of angular momentum at a specific time and the time change in direction of angular momentum) from in-situ debris measurements. This approach, as in previous studies, adopts a constraint equation derived from the fact that a piece of debris detected shares the geocentric position vector with an in-situ debris measurement satellite. However, unlike previous studies, this approach does not adopt a constraint equation that can be applied to the rate of change in right ascension of the ascending node of a broken-up object. Instead, this approach determines the inclination of a broken-up object from the maximum or minimum geocentric declination at the time of detection. Then, this approach finds out a candidate for the rate of change in right ascension of the ascending node of a broken-up object by assuming a circular orbit with a radius of the geocentric distance at the time of detection. Finally, using the constraint equation adopted, this approach estimates the right ascension of the ascending node at the time of breakup and calculates a correction for the rate of change in right ascension of the ascending node. This paper also verifies that this new approach works effectively under ideal conditions where all detections are assumed to be at the line of intersection of the two orbital planes of a broken-up object and an in-situ debris measurement satellite.

DOI： 10.3389/frspt.2022.867236

Web of Science

researchmap

その他リンク： https://doi.org/10.3389/frspt.2022.867236

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In This paper, we present an overview of space solar power satellite for the Moon and Mars mission. Simultaneously the compression of traditional methods of power generation for the orbiter, lander, and habitat on Mars and the Moon. The interplanetary mission where the space engineers are working on the satellite, conceptual design of space habitat, and exploration system. The state of the art in those missions relies on the radioisotope thermoelectric generator or solar panel attached with batteries to store power, which is plagued by certain limitations. For instance, when a spacecraft moves away from the sun, the collection efficiency of energy on the solar panel reduces, and if the temperature drops down below - 100Celsius, the attached solar array shows deteriorated performance than expected due to the unpredictable degradation of individual solar cells. Besides, these power generation unit satellites carry a pack of batteries to store energy, the total system makes more than 10-25% of the mass of the satellites. In hindsight, space solar power satellite serves a potential for a better source of energy transmission as compared to the traditional method. Space agencies have already studied space solar power station designing concept for gigawatts wireless power transmission system from space to earth to fulfill global electricity demand. Yet another avenue where space solar power satellites have an application is their utility towards rovers and habitat. On Mars, sandstorms affect the collection of energy at the attached solar panel to the rover. Moreover, the rovers are required to investigate at the far side of the Moon, where sunlight is unavailable for few days. This challenge can be suitably overcome by employing space solar power satellites, which can be used for wireless power transmission, independent of its location. Such techniques have possible applications towards power transmission for unmanned aerial vehicles for faster mapping purposes. As such, the dependence of those aerial vehicles towards fixed energy storage becomes alleviated.

DOI： https://doi.org/10.1016/j.jsse.2021.11.002

記述言語：英語   掲載種別：研究論文（学術雑誌）  

End-of-life support of satellites is necessary to improve post-mission-disposal compliance rates for maintaining space environment. Deorbit mission with low thrust, e.g. a laser, induces a low-level deceleration on the target object that gradually lowers the target altitude. Since such a low-thrust trajectory is time-consuming, the risk of collision greatly influences the mission success rate. In this context, this paper assesses the collision risk during deorbit trajectories with low thrust. Furthermore, parametric studies for the relationship between the re-entry time and the risk of collision are performed.

DOI： https://doi.org/10.1016/j.jsse.2021.11.002

出版者・発行元：Journal of Space Safety Engineering  

This paper presents an overview of space solar power satellites for the Moon and Mars mission and simultaneously demonstrates the compression of traditional power generation methods for the orbiter, lander, and habitat on Mars and the Moon. Interplanetary missions are where the space engineers work on the satellites, conceptual design of space habitat, and exploration system. The state of the art in those missions relies on radioisotope thermoelectric generators or solar panels attached with batteries to store power, both of which are plagued by limitations. For instance, when a spacecraft moves away from the Sun, the energy collection efficiency on the solar panel is reduced, and at temperatures below -100°Celsius, individual solar cells degrade unpredictably, deteriorating the performance of solar arrays. Furthermore, these power generation unit satellites carry a pack of batteries to store energy whose total system accounts for more than 10-25 % of the mass of the satellites. In an interplanetary mission, power generation and management are essential for research and investigation on the surface. For Mars, sandstorms affect the collection of energy at the attached solar panel to the rover. Moreover, the rovers must investigate at the far side of the Moon, where sunlight is unavailable for few consecutive days. This challenge can be suitably overcome by employing space solar power satellites, which can be used for wireless power transmission, independent of its location. Such techniques have possible applications towards power transmission for unmanned aerial vehicles for faster mapping purposes. As such, the dependence of those aerial vehicles towards fixed energy storage becomes alleviated. In hindsight, space solar power satellite serves as a potential for an improved energy transmission source than the traditional method for interplanetary rovers and habitat.

DOI： 10.1016/j.jsse.2021.10.008

Web of Science

Scopus

出版者・発行元：Journal of Space Safety Engineering  

End-of-life support of satellites is necessary to improve post-mission-disposal compliance rates for maintaining space environment. Deorbit mission with low thrust, e.g. a laser, induces a low-level deceleration on the target object that gradually lowers the target altitude. Since such a low-thrust trajectory is time-consuming, the risk of collision greatly influences the mission success rate. In this context, this paper assesses the collision risk during deorbit trajectories with low thrust. Furthermore, parametric studies for the relationship between the re-entry time and the risk of collision are performed.

DOI： 10.1016/j.jsse.2021.11.002

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 日本航空宇宙学会  

This paper aims to assess the risk of mission termination for a large constellation of satellites in a low-Earth orbit. Many large constellations will be deployed to provide broadband network services using thousands of satellites. There is concern that such large constellations will have a serious impact on the long-term sustainability of outer space activities due to the rapid increase in population. First, therefore, the authors conducted an assessment under nominal activities (referred to as “business-as-usual”) on the basis of a prediction by ESA’s MASTER-2009 and NASA standard breakup model 2001 revision. The assessment found that nearly one catastrophic collision may happen in a large constellation, generating more than two million fragments as small as 1mm in size. Second, the authors conducted a further assessment assuming a hypothetical collision of a satellite in a large constellation using the NASA standard breakup model and a spherical finite element model adopted in ESA’s MASTER-2009. In consequence, another catastrophic collision may happen to a large constellation, generating approximately a half-million fragments as small as 1 mm in size. Therefore, such catastrophic collisions and resulting secondary collisions should be prevented for large constellations.

DOI： 10.2322/tastj.20.10

CiNii Research

researchmap

リポジトリ公開URL： http://hdl.handle.net/2324/4755253

出版者・発行元：Proceedings of the International Astronautical Congress, IAC  

Because of its large number of satellites, a large constellation (an LC) greatly affects other objects in LEO. Several studies reveal the impact of an LC in LEO missions in various operational scenarios. This study evaluated the environmental impact of an LC explosion in the short and long-term using the Near-Earth Orbital Debris Environment Evolutionary Model (NEODEEM). Although setting mission scenarios and analysis conditions is important in LC simulations, it is difficult to consider all operational scenarios due to the many combinations. Therefore, this study conducted impact assessments of explosions in an LC, concentrating on the number of explosions, orbital altitude, and scaling factor of the explosions. The results indicated that it is not enough for LC to comply with the current requirement of probability of accidental explosions which is less than 0.001 during the operation. This is because, if the rate is applied directly to an LC with thousands of satellites, continuous explosions (i.e., several satellites explode every year) will occur during the duration of LC. The paper also discusses the behavior of fragments from explosions at different altitudes. The explosions at low altitudes have no significant impact in the long term, although it can cause an incremental change in collision risk in the short term. Similarly, the explosions at high altitudes, such as 1,250 km, have only slightly increments of the expected number of collisions, but its impact could last for over 100 years. The probability of explosions of an LC must be carefully determined through a series of simulations based on the number of satellites and the operational orbit of an LC. This paper also discusses what should be considered in future LC design and operations regarding explosion prevention.

Scopus

出版者・発行元：Proceedings of the International Astronautical Congress, IAC  

Space-advertisement is getting closer with advances in satellite formation flying, which displays an artificial constellation in the night sky. The formation shape composed of pixels of satellites equipping light sources is observed from the ground and different from formation in relative orbits. For realizing the advertisement shape of high quality, there are two requirements, placing the pixels of the advertisement shape properly and keeping the shape during a visible span. It is not enough to satisfy the requirements by the usual coordinate systems and equations. Considering a topocentric coordinate system, the new transforming equations are derived so that an arbitrary advertisement shape is designed at the target time. Also, stable orbits that keep the formation shape without control are found and an example of stable orbits is presented.

Scopus

出版者・発行元：Proceedings of the International Astronautical Congress, IAC  

The 21st century is marked by the unprecedented progress of human knowledge in space, quantum mechanics, and machine learning. This progress has in turn lead to a significant increase in satellite launches, with various organizations developing mega-constellations in space to provide new business opportunities. While current predictions estimate that space in Low Earth Orbit will be overcrowded in the future, and sustainability of space will become a critical question as the estimated traffic of 89,000 satellites will be launched by the year 2035. To allow sustainable development of space, especially in Low Earth Orbit, there is a need to develop accurate traffic management and active debris removal mission planning. Lately, several organizations proposed and completed space demonstration experiments for debris removal. Current their designs are part of an ongoing project to develop contact-based debris removal technology. However, this technology poses several problems for satellite removal. We propose a complementary method based on a laser system. The laser is capable to operate from a safe distance by stopping the continuous rotation (detumbling) of space objects. In this paper, we present a case study using the ENVISAT satellite. ENVISAT is an 8,211 kg satellite, launched by European Space Agency. Since 2012, communication has stopped, and it is no longer operational. It is predicted to self-deorbit in the next 150 years. However, the orbital simulation of existing objects found two cataloged space debris which will pass within 200 m., resulting in a close approach every year. The elevated mass of the satellite and the number of close approaches, therefore, pose a considerable threat, leading to the production of debris. SKY Perfect JSAT Corporation is working jointly with Japanese institutions to collaboratively develop laser satellites to stop detumbling and the careful removal of debris. The demonstration mission will be launched by the year 2026-2027. With this case study, a laser-based contactless method can be practiced for removing mega debris like ENVISAT from the Low Earth Orbit.

Scopus

出版者・発行元：Proceedings of the International Astronautical Congress, IAC  

Laser ablation is a vital technology for contactless active debris removal, where a service satellite with a laser system irradiates laser pulses to a target satellite to generate the ablation force for deorbiting. The deorbiting force decelerates the target, and the service satellite needs to maintain its relative position and keep irradiating. In other words, both the service satellite and the target are supposed to be deorbited simultaneously, where both satellites have accelerations. The difficulty of simultaneous deorbiting stems from the relative motion between the service satellite and the target in powered flight because conventional formation flying missions assume that only a service satellite maneuvers. This paper derives the relative equations of motion between the service satellite and the target in powered flight. A control law for the simultaneous deorbit is proposed, which determines the timing and direction of the laser ablation and the electrical thrust so that the formation periodically returns to the desired formation. Numerical simulations are performed for two test cases to verify the control law under the uncertainties of thrust magnitude and orbital perturbation.

Scopus

出版者・発行元：Proceedings of the International Astronautical Congress, IAC  

Collisions and explosions of satellites generate a large amount of sub-millimeter-size debris, which can cause fatal damage to a spacecraft. However, such tiny debris cannot be tracked from the ground. Therefore, an in-situ debris measurement satellite, which can detect impacts with sub-millimeter-size debris, has been proposed. Based on this concept, previous studies proposed the method to estimate some orbital parameters of the broken-up object. In those studies, it is assumed that the measurement satellite detects impacts at the intersection of the orbital planes of the measurement satellite and the broken-up object. However, simulated measurement data includes fragments contrary to this assumption. Thus, this study introduces a new approach to estimating the orbital parameters of the broken-up object from simulated measurement data. In this study, the inclination, the right ascension of the ascending node, and the nodal precession rate are estimated from the history of geocentric declination using the iteratively reweighted nonlinear least square method.

Scopus

記述言語：英語   出版者・発行元：宇宙太陽発電学会  

<p>Wireless Power Transmission (WPT) technology using a satellite-to-satellite system represents a valuable and convenient technology for transferring power wirelessly among Space Solar Power Satellites (SSPS) to Satellite and potential upcoming interplanetary missions. This direct transmission offers a possible solution to deliver continuous, convenient, and unlimited energy supply to satellites to help replace traditional power storage and reduce the weight and ultimately the costs of launching satellites. Satellite industries traditionally use photovoltaic cells and nuclear generators to satisfy the needed electricity by spacecraft. Current power generation and effective management systems occupy up to 10-25% of the satellite's mass. The concept of laser-based WPT from Energy Satellite (E-Sat) can overcome substantial problems. This consistent idea can be adopted for spacecraft by developing a constellation of E-Sat called Energy Orbit (E-Orbit) to supply sufficient power to spacecraft within range. It will increase the impressive performance and operational lifetime. In addition, creating 1600 E-Sat’s constellations to fulfill the power demand in Low Earth Orbit. The overall efficiency variation depends on the selection of Laser, transmitter, transmission distance, and photovoltaic cells, the same as increasing the maximum transmission efficiency of information in a wireless communication network. Consequently, in general, and adequate guidelines of the satellite-to-satellite power transmission system design in practice. The development and demonstration of this technology can help fulfill Space Solar Power Satellite’s idea to transfer gigawatts of renewable energy to Earth.</p>

DOI： 10.24662/sspss.7.0_12

CiNii Research

出版者・発行元：Proceedings of the International Astronautical Congress, IAC  

Solar radiation pressure (SRP) is a major disturbance for a spacecraft operated in deep space missions, affecting its orbit and attitude, and high accuracy of the SRP calculation is required. The accuracy of SRP calculation is affected by the shape and surface characteristics of the satellite. However, existing computational models do not sufficiently take into account the exact reflective properties of the satellite surface. A detailed reflection model and considering the optical characteristics yield a different SRP and its torque from the conventional ones, resulting in a different attitude motion. In this study, an SRP calculation method that considers the exact reflective properties is applied to investigate the attitude dynamics.

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study aims to develop an effective strategy for geostationary satellites to avoid collisions with space debris satisfying various operational constraints. Recently, the number of space objects is continuously increasing to threaten operational satellites in the geostationary region. Studies on collision avoidance have been advanced for a long time, but not sufficiently considered orbit maintenance after maneuvering. Not to shorten satellite lifetime by collision avoidance, it is necessary to consider orbit maintenance after maneuvering. Besides, orbit maintenance regularly conducted differs between chemical thruster and electric thruster, so that two different avoidance strategies may be required. This study adopts a Multi-objective Genetic Algorithm to find out an optimal strategy for each thruster under various constraints on the operation. This paper also demonstrates that the optimal collision avoidance maneuvering can achieve both collision avoidance and orbit maintenance with less fuel than regular orbit control.

DOI： https://doi.org/10.1016/j.jsse.2021.08.004

リポジトリ公開URL： http://hdl.handle.net/2324/4741657

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Wireless Power Transmission technology using a satellite-to-satellite system represents a valuable and convenient technology for transferring power wirelessly among Space Solar Power Satellites to Satellite and potential future interplanetary missions. This direct transmission can help replace traditional power storages and reduce the weight and ultimately the costs of launching satellites. This paper discusses the Wireless Power Transmission between one small-scale Space Solar Power Satellite to another operational satellite, followed by a demonstration of small-scale Space Solar Power Satellites and evaluating the possibility for future implementation. It will increase the performance and operational lifetime, especially for small and cube satellites using microwaves and laser-based power transmission. The development and demonstration of this technology can help fulfill Space Solar Power Satellites idea to transfer gigawatts of renewable energy to Earth.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2514/1.G005877

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2514/1.G004966

リポジトリ公開URL： http://hdl.handle.net/2324/4481550

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Space debris smaller than 2 mm that cannot be detected by ground-based observations may lead to a spacecraft's mission end. Therefore, multiple institutes and organizations have conducted in-situ measurement projects including the IDEA (In-situ Debris Environmental Awareness) project, which has been initiated at Kyushu University. The previous research has proposed a statistical method that estimates the environment of sub-millimeter-size debris sequentially utilizing in-situ measurements. This paper aims to improve accuracy of the estimation result by a “feedback estimation” method that utilizes the measurement data multiple times. Furthermore, this paper also calculates “total likelihood” to evaluate the accuracy of estimation results quantitatively so that effectiveness of the feedback estimation can be discussed. The evaluation with the total likelihoods suggests that the feedback estimation method can increase the accuracy of the environmental estimation. In conclusion, this paper contributes the improvement in the environmental estimation on sub-millimeter-size debris utilizing in-situ measurement.

DOI： 10.2322/tastj.18.276

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Orbital debris (OD) remains as an obstacle to further space development. While efforts are ongoing to avoid newly launched objects becoming debris, the number of debris would still continue to grow because of collisions. Active debris removal (ADR) is an effective measure, but building a sustain- able economic model for ADR remains as a difficult problem. We propose that the cost of removal can be paid by circulating digital currency tokens on a blockchain platform whose values may decrease and/or increase over time, issued by global cooper- ation (a consortium) of parties interested in space development, in exchange with proofs of ADR. The tokens pay their cost by themselves through contributions by the token holders, who are likely to be benefited by removal of debris. This scheme imposes virtually no cost to the consortium. We have generalized this concept as proof of disposal, which, we believe, provides a more accountable foundation for solving social problems with digital currency than many Initial Coin or Cryptoasset Offering in practice today. We evaluated the feasibility of our proposal through a simulation. We conclude that dynamic estimation of the economic values of each ADR and automated pricing of tokens that represent the OD being removed are indeed possible. Actual prototyping of the proposed digital currency system is ongoing.

DOI： https://doi.org/10.1109/TCSS.2018.2890655

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Even sub-millimeter-size debris could cause a fatal damage on a spacecraft. Such tiny debris cannot be followed up or tracked from the ground. Therefore, Kyushu University has initiated IDEA the project for In-situ Debris Environmental Awareness, which conducts in-situ measurements of sub-millimeter-size debris. One of the objectives is to estimate the location of on-orbit satellite fragmentations from in-situ measurements. The previous studies revealed that it is important to find out the right nodal precession rate to estimate the orbital parameters of a broken-up object properly. Therefore, this study derives a constraint equation that applies to the nodal precession rate of the broken-up object. This study also establishes an effective procedure to estimate properly the orbital parameters of a broken-up object with the constraint equation.

DOI： https://doi.org/10.1016/j.asr.2018.07.034

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Debris mitigation measures such as post-mission disposal (PMD) were set by considering the effects thereof using a debris evolutionary model. Many small satellites have recently been deployed in orbit and various plans are proposed for a so-called mega-constellation consisting of thousands of satellites in Low Earth Orbit (LEO). New systems such as an electric propulsion system and air drag augmentation devices are also proposed for satellite de-orbit. Therefore, the impact of them must be discussed in order to preserve the space environment. This study evaluates the debris mitigation measures taken by using the Near-Earth Orbital Debris Environment Evolutionary Model (NEODEEM) that was jointly developed by Kyushu University and JAXA. It revealed that mega-constellations have much impacts on the debris environment, and that the future environment will be affected by the PMD compliance rate and how PMD is achieved.

DOI： 10.2322/tastj.16.599

記述言語：英語   掲載種別：研究論文（学術雑誌）  

To date, there has been a lot of on-orbit satellite fragmentations since a Thor-Able upper stage exploded in space in 1961. Considering that even sub-millimeter-size debris are a big threat to operational satellites, then it can be said that detailed debris modelling is becoming an urgent task for sustainable space development. For accurate modelling, it is essential to know the accurate time of breakup. However, there is no effective method which can estimate the time precisely. Therefore, this study aims at constructing a new method for estimating the time of breakup precisely. This study focuses on orbital plane as a parameter and derives a new equation. This equation constraints orbital planes of fragments at breakup by using orbital elements of the broken-up object. The ad- vantage of this equation is that the fragments can be evaluated by only inclination and right ascension of the ascending node which can guarantee relatively high accuracy even in a long-term propagation. For the esti- mation, this study proposes a hybrid method which combines the advantages of the constraint equation and the close approach analysis. As a result, by using officially reported data, it was confirmed that this hybrid method can estimate the time of breakup with an error of 1 min or less. It was also suggested that the difference in the estimated time between the hybrid method and the close approach analysis causes a large difference in predicted fragments.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Space debris smaller than 2 mm that cannot be detected by ground-based observations may lead to a spacecraft’s missions end. There- fore, IDEA, the project for In-situ Debris Environmental Awareness, which aims to detect sub-millimeter-size debris using a group of micro satellites, has been initiated at Kyushu University. To estimate the debris environment based on in-situ measurements from the project, this paper proposes an environmental estimation model with a Sequential Monte Carlo (SMC) filter. First, this paper reviews the previous research that investigated the nature of an orbit on which a piece of debris can be detected through in-situ measurements, and applies this phenomenon to the algorithm of the SMC filter. Second, the proposed model is evaluated by a simulation using MASTER-2009, which is the environmental model developed at European Space Agency. Comparison between the debris distributions predicted by MASTER-2009 and the simulated estimation verifies that the proposed model can estimate the debris environment suffi- ciently. Finally, this paper also investigates the effect of the measurement duration on the estimation. It is concluded, therefore, that the estimation model proposed and evaluated in this paper can provide a better definition of the sub-millimeter-size debris environment with in-situ measurements.

DOI： https://doi.org/10.1016/j.asr.2018.04.042

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The growth of the near-Earth debris population since the beginning of human space activities is now a fact commonly admitted by space agencies worldwide. Numerous entities have warned about the danger that debris may have over time. Presently mitigation meth- ods such as imposing post-mission disposal time after launch will no longer be sufficient; remediation processes seem necessary to limit the increase. In particular, this phenomenon is attributed to the generation of fragments due to more and more on-orbit collisions. There- fore, investigations on indexes to select potential removal targets were recently conducted, considering solely objects implicated in a col- lision course. This study also looks at the multiple fragmentation factors, including time through the altitude at time of impact (due to the behaviour of debris re-entering with time).
The focal point is here to compare different criteria to select removal targets that enable scenarios in best adequacy with the future in question (long term, mid term or short term). Aware of the uncertainty of evolutionary models, this study also incorporates the simu- lation method as an impactful factor and tries to overcome the potential randomness of the results. Therefore, this paper presents a way to establish a selection criterion the most adequate for the time period focused on.
In order to solve this issue, a ‘‘double-check” method is proposed. First, an analytical evolutionary model simulates the environment over 100 years, through 100 Monte-Carlo runs. Then, among the initial population of year 2009, the objects supposed to be at the origin of the debris detected at a given time are tracked back in time into the simulations, using a collision-detecting program. The ‘‘given per- iod” above mentioned for the presence of debris is based on a future as such that 2029 be considered a short-term scenario, 2059 a mid- term scenario and 2109 a long-term scenario. This step produces three lists of targets for removal (one for each future), and simulations are run once again, through different scenarios involving the removal of particular listed targets in order to verify the appropriateness of the proposed scenarios. The analysis of the results is based both on the mean of the simulations and on the recurrence considering each run.
Three studies were conducted one for each term, and a fourth one completed the work by establishing comparison between short, mid and long-term periods. As a result, three main criteria could be established: the altitude of the objects, the number of targets necessary to remove, and the phenomenon of chain collisions. According to the future that was investigated, the most adequate criterion appeared to be different, consisting in the number of objects in the long-term analysis or the ranking position at short term (linked to the close-time consideration). As a main conclusion and further perspectives, it should be more efficient to consider the collision-probability and mass product together with the time-depending generation of fragments. This would help increasing the precision in the prediction of collision impacts.
Rather than pinpointing specified targets to be removed, the aim of this study is simply to understand the mechanisms at the origin of the population increase around the Earth. Also to demonstrate that a careful definition of selection criteria would enable to adopt a suitable removal process in the period of action or for the goal to be reached.

DOI： http://dx.doi.org/10.1016/j.asr.2017.05.046

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This work aims to study the effect of conservative and non-conservative forces, like Earth’s oblateness, third-body gravitational attraction and atmospheric drag on satellites in high elliptical Molniya and Tundra orbit types for coverage of high latitude regions. This work uses a Kyushu University computational model to make a simulation to propagate the effect of various perturbations on satellites constellation in Tundra and Molniya orbits for 10 years. The computational Model solves the Gaussian planetary equations numerically under effect of orbit perturbations and gives a high accuracy for the interval of propagation for Tundra and Molniya satellites constellations. The results show that the effect of theses forces on different eccentricities 0.2~0.7 is varying, and the daily coverage hours for this satellites constellation increase and decrease according to the change in the argument of perigee or the right ascension of the ascending node. Hence, the over lapping between these satellites in the constellation will be affected. A non-coplanar maneuver done for the satellites that affected by perturbations to correct their positions in order to make a continuous coverage.

その他リンク： https://www.onlinejournal.in/IJIRV3I9/127.pdf

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents a novel method to simultaneously detect multiple trajectories of space debris in an observation image sequence to establish a reliable model for space debris environment in Geosynchronous Earth Orbit (GEO). The debris in GEO often appear faintly in image sequences due to the high altitude. A simple but steady way to detect such faint debris is to decrease a threshold value of binarization applied to an image sequence during preprocessing. However, a low threshold value of binarization leads to extracting a large number of objects other than debris that become obstacles to detect debris trajectories. In order to detect debris from binarized image frames with massive obstacles, this work proposes a method that utilizes a cascade of numerical evaluations and a voting scheme to evaluate characteristics of the line segments obtained by connecting two image objects in different image frames, which are the candidates of debris trajectories. In the proposed method, the line segments corresponding to objects other than debris are filtered out using three types of characteristics, namely displacement, direction, and continuity. First, the displacement and direction of debris motion are evaluated to remove irrelevant trajectories. Then, the continuity of the remaining line segments is checked to find debris by counting the number of image objects appearing on or close to the line segments. Since checking the continuity can be regarded as a voting scheme, the proposed cascade algorithm can take advantage of the properties of voting method such as the Hough transform, i.e., the robustness against heavy noises and clutters, and ability of detecting multiple trajectories simultaneously. The experimental tests using real image sequences obtained in a past observation campaign demonstrate the effectiveness of the proposed method.

DOI： http://dx.doi.org/10.1016/j.actaastro.2016.10.032

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Space debris smaller than 1 mm in size still have enough energy to cause a fatal damage on a spacecraft, but such tiny debris cannot be followed or tracked from the ground. Therefore, IDEA the project for In-situ Debris Environmental Awareness, which aims to detect sub-millimeter-size debris using a group of micro satellites, has been initiated at Kyushu University. First, this paper reviews the previous study on the nature of orbits on which debris may be detected through in-situ measurements proposed in the IDEA project. Second, this paper derives a simple equation that constrains the orbital plane on which debris is detected through in-situ measurements. Third, this paper also investigates the nature and sensitivity of this simple constraint equation to clear how frequently impacts have to be confirmed to reduce the measurement error. Finally, this paper introduces a torus model to describe the collision flux observed from the previous study approximately. This collision flux approximation agrees rather well with the observed collision flux. It is concluded, therefore, that the simple constraint equation and collision flux approximation introduced in this paper can replace the analytical method adopted by the previous study to conduct a further investigation more effectively.

DOI： http://dx.doi.org/10.1016/j.asr.2016.12.036

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Inspired by successful extended missions such as the ISEE-3, an investigation for the extended mission that involves a lunar encounter following a Sun-Earth halo orbit mission is considered valuable. Most previous studies present the orbit-to-orbit transfers where the lunar phase is not considered. Intended for extended missions, the present work aims to solve for the minimum phasing ΔV for various initial lunar phases. Due to the solution multiplicity of the two-point boundary value problem, the general constrained optimization algorithm that does not identify multiple feasible solutions is shown to miss minima. A two-step differential corrector with a two-body Lambert solver is developed for identifying multiple solutions. The minimum ΔV associated with the short-way and long-way approaches can be recovered. It is acquired that the required ΔV to cover all initial lunar phases is around 45 m/s for the halo orbit with out-of-plane amplitude Az greater than 3.5×10^5 km, and 14 m/s for a small halo orbit with Az = 1×10^5 km. In addition, the paper discusses the phasing planning based on the ΔV result and the shift of lunar phase with halo orbit revolution.

DOI： http://dx.doi.org/10.1016/j.actaastro.2016.05.003

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper investigates the Earth escape for spacecraft in a Sun-Earth halo orbit. The escape trajectory consists of first ejecting to the unstable manifold associated with the halo orbit, then coasting along the manifold until encountering the Moon, and finally performing lunar-gravity-assisted escape. The first intersection of the manifold tube and Moon’s orbit results in four intersection points. These four manifold-guided encounters have different relative velocities (v ̈) to the Moon; therefore, the corresponding lunar swingbys can result in different levels of characteristic energy (C3) with respect to the Earth. To further exploit these manifold-guided lunar encounters, subsequent swingbys utilizing solar perturbation are considered. A graphical method is introduced to reveal the theoretical upper limits of the C3 achieved by double and multiple swingbys. The numerically solved Sun-perturbed Moon-to-Moon transfers indicate that a second lunar swingby can efficiently increase C3. Compared to the direct low-energy escape along the manifold, applying a portion of the lunar swingbys before escape is shown to be more advantageous for deep-space mission design.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Currently, the danger due to debris in earth orbit is increasing. Furthermore, methods for the removal of such orbital debris have become the subject of attention. This paper proposes a concept for passive Orbital Debris Removal (ODR). In the passive ODR described in this research, a large area of polyimide foil is opened. Low earth orbit micro-debris decelerate due to their passing through the opened foil, and eventually reenter the atmosphere. In order to achieve efficient debris removal, as part of this research an unfolding mechanism has been invented that can open a large area of polyimide foil in low earth orbit. To demonstrate the effectiveness of this orbital debris removal concept, an event equivalent to the breaking up of a satellite by Chinese anti-satellite testing has been assumed. In order to give consideration to the perturbation of the orbital debris removal spacecraft, removal effectiveness was compared with regard to the direction of orbit injection, the effective cross sectional area, and orbit injection time as parameters.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper briefly introduces efforts into space debris modeling towards a better understanding of space debris environment. Space debris modeling mainly consists of debris generation and orbit propagation. Debris generation can characterize and predict physical properties of fragments originating from explosions or collisions. Orbit propagation can characterize, track, and predict the behavior of individual or groups of space objects. Therefore, space debris modeling can build evolutionary models as essential tools to predict the stability of the future space debris populations. Space debris modeling is also useful and effective to improve the efficiency of measurements to be aware of the present environment.

DOI： http://dx.doi.org/10.20910/IJASE.2016.3.1.5

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study proposes an algorithm to detect orbital objects that are small or moving at high apparent velocities from optical images by utilizing their faint streaks. In the conventional object-detection algorithm, a high signal-to-noise-ratio (e.g., 3 or more) is required, whereas in our proposed algorithm, the signals are summed along the streak direction to improve object-detection sensitivity. Lower signal-to-noise ratio objects were detected by applying the algorithm to a time series of images. The algorithm comprises the following steps: (1) image skewing, (2) image compression along the vertical axis, (3) detection and determination of streak position, (4) searching for object candidates using the time-series streak-position data, and (5) selecting the candidate with the best linearity and reliability. Our algorithm’s ability to detect streaks with signals weaker than the background noise was confirmed using images from the Australia Remote Observatory.

DOI： http://dx.doi.org/10.1016/j.asr.2015.10.034

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This work proposes a method to determine orbital plane of a micron-sized space debris cloud utilizing their impacts on measurement satellites. Given that debris impacts occur on a line of intersection between debris and satellites orbital planes, a couple of debris orbital parameters, right ascension of the ascending node, inclination, and nodal regression rate can be determined by impact times and locations measured from more than two satellites in different earth orbits. This paper proves that unique solution for the debris orbital parameters is obtained from the measurement data, and derives a computational scheme to estimate them. The effectiveness of the proposed scheme is finally demonstrated by a simulation test, in which measurement data are obtained from a numerical simulation considering realistic debris’ and satellites’ orbits.

DOI： http://dx.doi.org/10.1016/j.asr.2015.11.005

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper introduces an effort to precisely describe attitude motion under full orbit perturbations. To define the attitude of an Earth-orbiting spacecraft, this study introduces a reference frame being affected by orbit perturbations. Unlike the commonly adopted reference frame, the reference frame introduced here is fully perturbed, so that it rotates about not only the pitch axis, but also the yaw axis. To incorporate the mutual coupling effect between attitude motion and orbit motion, the method introduced considers the spacecraft as consisting of multiple facets and carefully models orbit perturbation-induced torque that varies the attitude. This paper focuses on the attitude dynamics of a small satellite with relatively low moments of inertia under full orbit perturbations, and provides some interesting results and the outcome from the method introduced.

DOI： http://doi.org/10.2322/tastj.13.45

リポジトリ公開URL： http://hdl.handle.net/2324/4402934

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The In-Situ Debris Environment Awareness System has been developed. The objective of the system is to measure small debris (between 100 μm and several cm) in orbit. The orbital distribution and the size distribution of the debris are not well understood. The size distribution is difficult to measure from the ground, although the size distribution is very important for the risk evaluation of the impact of debris on spacecraft. The in-situ measurement of the size distribution is useful for: 1) verification of meteoroid and debris environment models, 2) verification of meteoroid and debris environment evolution models, 3) real time detection of unexpected events, such as explosions and/or collisions on an orbit. This paper reports the development study of the in-situ debris measurement system and shows demonstration experiments and their results to describe the performance of the micro-debris sensor system. The sensor system for monitoring micro-debris with sizes ranging from 100 μm to a few mm must have a large detection area, while the constraints of space deployment require that these systems be low in mass, low in power, robust and have low telemetry requirements. For this reason, we have been developing a simple trans-film sensor. Thin and conductive stripes (copper) are formed with fine pitch (100 μm) on a thin film of nonconductive material (12.5-μm thick polyimide). A hypervelocity micro-particle impact is detected when one or more stripes are severed by perforation of the film. We designed a debris detector specialized for measuring the micro-debris size and collision rate. We then manufactured and calibrated the detector.

DOI： http://dx.doi.org/10.1016/j.asr.2015.04.009

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

The number of small satellites as those that do not exceed 50kg is rapidly increasing in the low-Earth orbit region. Since the orbital debris mitigation guidelines released by United Nations, Inter-Agency Space Debris Coordination Committee and national space agency does not consider small satellites and typical large satellites separately, small satellites also should conduct post-mission disposal. However most small satellites are launched as piggyback satellites, affordable post-mission disposal of small satellites is different from that of typical large satellites, and this post-mission disposal of small satellites may cause the collisions to other satellites. For developers of small satellites, this paper introduces the effect of small satellites post-mission disposal on sustainable space utilization, which was presented by the authors in previous.

DOI： http://dx.doi.org/10.1109/RAST.2015.7208446

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Unnecessary artificial objects, or so-called space debris, orbiting Earth contaminate the orbital environment and represent a serious problem for sustainable space development and use. One fundamental debris countermeas- ure is object tracking and cataloging. Such catalogs allow spacecraft mission risk assessment and the conducting of collision-avoidance maneuvers. However, the SpaceTrack object catalog released to the public is insufficient be- cause the catalog includes relatively large objects (> 10 cm), only. We propose using two space-based sensors to address this problem and analyze their observational and tracking capabilities. Initial results suggest that approxi- mately 4.2% of objects in low Earth orbit in size of 5-10 cm could be detected by space-based sensors. We also propose collaborative observations with a network of ground-based observatories. The space-based sensors are for detection and initial orbit determination, and the ground-based observatories are for catalog maintenance under collaboration with the space-based sensors. Initial orbit estimates from space-based sensors enable ground ob- servatories to employ the image stacking method. Simulated differences between predicted and true apparent posi- tions and motions indicate that it is possible to observe a target based on orbital data from space-based sensors.

DOI： http://dx.doi.org/10.2322/tastj.12.Pr_27

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Developers of small satellites may think of enlarging their effective cross-sectional area to minimize the long-term presence in the low Earth orbit region. However, the enlargement of their effective cross-sectional area causes the temporal increase of cumulative probability of accidental collisions. This paper evaluates the influence of small satellites’ post-mission disposal by enlarging their cross-sectional area on the future population using an orbital debris environment evolutionary model. According to the result of the future projections, the small satellites’ post-mission disposals by enlarging the effective cross-sectional area have the potential risk of increasing the accidental collision. However small satellites are inserted into orbit below 800 km in this paper, the fragments to be generated by collision expected to decay within short term. The effective number of objects below 2,000 km altitude is not different between the case with post-mission disposals and the case without post-mission disposals.

DOI： http://dx.doi.org/10.2322/tastj.12.Pr_21

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

The purpose of this study is to research about removal effectiveness of debris removal spacecraft. It was investigated whether debris would be removable in one year using the property of spacecraft proposed by the first research. The removal method is passive debris removal. The assumed break up event is equivalent to Chinese Anti Satellite test that occurred in January, 2007. In consideration of a removal spacecraft moving by perturbation, removal effectiveness was compared for directions of orbit injection, effective cross sectional area, and orbit injection time as a parameter.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper demonstrates an initial orbit determination method that solves the problem by a genetic algorithm using two well-known solutions for the Lambert’s problem: universal variable method and Battin method. This paper also suggests an intuitive error evaluation method in terms of rotational angle and orbit shape by separating orbit elements into two groups. As reference orbit, mean orbit ele- ments (original two-lines elements) and osculating orbit elements considering the J2 effect are adopted and compared. Our proposed orbit determination method has been tested with actual optical observations of a geosynchronous spacecraft. It should be noted that this dem- onstration of the orbit determination is limited to one test case. This observation was conducted during approximately 70 min on 2013/ 05/15 UT. Our method was compared with the orbit elements propagated by SGP4 using the TLE of the spacecraft. The result indicates that our proposed method had a slightly better performance on estimating orbit shape than Gauss’s methods and Escobal’s method by 120 km. In addition, the result of the rotational angle is closer to the osculating orbit elements than the mean orbit elements by 0.02°, which supports that the estimated orbit is valid.

DOI： http://dx.doi.org/10.1016/j.asr.2013.11.051

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Upper atmospheric densities during geomagnetic storms are usually poorly estimated due to a lack of clear understanding of coupling mechanisms between the thermosphere and magnetosphere. Consequently, the orbit determination and propagation for low-Earth-orbit objects during geomagnetic storms have large uncertainties. Artificial neural networks are often used to identify nonlinear systems in the absence of rigorous theory. In the present study, an attempt has been made to model the storm-time atmospheric density using neural networks. Considering the debate over the representative of geomagnetic storm effect, i.e. the geomagnetic indices ap and Dst, three neu- ral network models (NNM) are developed with ap, Dst and a combination of ap and Dst respectively. The density data used for training the NNMs are derived from the measurements of the satellites CHAMP and GRACE. The NNMs are evaluated by looking at: (a) the mean residuals and the standard deviations with respect to the density data that are not used in training process, and (b) the accuracy of reconstructing the orbits of selected objects during storms employing each model. This empirical modeling technique and the compar- isons with the models NRLMSIS-00 and Jacchia-Bowman 2008 reveal (1) the capability of neural networks to model the relationship between solar and geomagnetic activities, and density variations; and (2) the merits and demerits of ap and Dst when it comes to char- acterizing density variations during storms.

DOI： http://dx.doi.org/10.1016/j.asr.2013.11.052

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The orbital debris modeling can build evolutionary models as essential tools to predict the current or future orbital debris populations, and also to discuss what and how to do for orbital debris mitigation and environmental remediation. The orbital debris modeling can also devise an effective search strategy applicable for breakup fragments in the geostationary region using ground-based optical sensors, and to evaluate the effectiveness of space-based measurements of objects not tracked from the ground, both to contribute to space situational awareness. Another application of the orbital debris modeling is to estimate attitude motion of space objects to be removed for environmental remediation. This paper briefly introduces efforts into orbital debris modeling and applications at Kyushu University.

DOI： 10.1016/j.proeng.2013.12.040

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The presence of orbital debris is a potential risk for sustainable space development and its utilization for humankind. Prevention of large-scale spacecraft breakup events is a crucial part of countermeasures against orbital debris, and one of the key related technologies is the collision avoidance maneuver. Current observations are insufficient to track objects smaller than 10 cm, which are still large enough to cause catastrophic damage to primary spacecraft. The final goal of this study is to track debris 1 cm and larger in the low Earth orbit region. This paper proposes a space-based optical measurement system as a new promising solution. There are three points to be followed: 1) observation opportunity, 2) orbit determination accuracy and 3) tracking capability. As the first step, this paper focuses on assessing observation opportunity using a newly developed space-based observation simulator. This paper summarizes assessment results in terms of the number of passing objects, imaged objects, image moving velocity in pixels, apparent magnitude, observation occurrence frequency with respect to the observer’s true anomaly, and the relationship between the observation count and interval.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper proposes to apply the space debris modeling techniques to devise an effective search strategy applicable for breakup fragments in the geostationary region. The space debris modeling techniques describe debris generation and orbit propagation to effectively conduct predictive analyses of space objects that include characterizing, tracking, and predicting the behavior of individual and groups of space objects. Therefore, the techniques can predict population of debris from a specific breakup event. The population prediction specifies effectively when, where, and how optical measurements using ground-based telescopes should be conducted. The space debris modeling techniques can also predict motion of debris in successive images taken with ground-based telescopes. The motion prediction specifies effectively and precisely how successive images of objects in the geostationary region should be processed. This paper also validates the proposed search strategy through actual observations, targeting the U.S. Titan IIIC Transtage explosion in the geostationary region.

DOI： 10.2514/1.A32228

記述言語：英語   掲載種別：研究論文（学術雑誌）  

his paper proposes a comprehensive approach to associate origins of space objects newly discovered during optical surveys in the geostationary region with spacecraft breakup events. A recent study has shown that twelve breakup events would be occurred in the geostationary region. The proposed approach utilizes orbital debris modeling techniques to effectively conduct prediction, detection, and classification of breakup fragments. Two techniques are applied to get probable results for origin identifications. First, we select an observation point where a high detection rate for one breakup event among others can be expected. Second, we associate detected tracklets, which denotes the signals associated with a physical object, with the prediction results according to their angular velocities. The second technique investigates which breakup event a tracklet would belong to, and its probability by using the k-nearest neighbor (k-NN) algorithm.
In this paper we conduct optical observations of breakup fragments to verify the proposed approach. We selected a well-known breakup event of the rocket body US Titan 3C Transtage (1968-081E) as the primary observation target, and then we conduct optical observations by campaign between two sensors in Taiwan and one sensor in Japan. While three nights observations, we detect 96 trac- klets that are uncorrelated with the Space Surveillance Network catalogue at the observation epochs, and finally 50 tracklets among them are associated with the breakup event of 1968-081E.

DOI： http://dx.doi.org/10.1016/j.asr.2013.02.008

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The Space Debris Mitigation Guidelines of the Scientific and Technical Subcommittee of the United Nations Committee on the Peaceful Uses of Outer Space consist of seven guidelines to be considered for the mission planning, design, manufacturing and operational (launch, mission and disposal) phases of spacecraft and launch vehicle orbital stages. In order to compare small satellites with large satellites in terms of impact on the orbital debris environment, this paper focuses on guideline 3 in the mitigation guidelines, which limit the probability of accidental collision in orbit. The probability of accidental collision is a function of the effective cross-sectional area. Large satellites have a larger effective cross-sectional area in comparison to small satellites, so that large satellites specify a higher probability of accidental collision than small satellites do. The number of fragments to be generated by a collision is a function of mass. Therefore, in the comparison to small satellites, large satellites also generate more fragments and add them to the environment.

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

This paper focuses on a collision risk of a tether system against other satellites. The tether system in this paper means a spacecraft for orbital debris removal using an electro-dynamic tether, and is expected to prevent the population growth of orbital debris in the low Earth orbit region. However, the tether system may encounter a high collision risk because of its thin and long configuration. Therefore, there is a possibility that the tether system collides with other orbiting satellites when the tether system conducts a mission of orbital debris removal. This paper estimates the collision probability and the success rate until the orbital debris removal mission is over and describes factors contributing to the reduction in the mission success rate.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper briefly introduces efforts made at Kyushu University in the area of orbital debris modeling and applications. The orbital debris modeling, which describes debris generation and orbit propagation, enables us to build orbital debris evolutionary models as essential tools to predict the future orbital debris population, and as applications to discuss what and how to do for orbital debris mitigation and remediation. The orbital debris modeling also enables us to devise an effective search strategy applicable for breakup fragments in the geostationary region using ground-based optical sensors, and to evaluate the effectiveness of space-based measurements of objects not tracked from the ground, both to contribute to space situational awareness. Ultimately, this paper includes atmospheric density modeling necessary for orbital decay and re-entry analyses, and space tether modeling to assess risks of using electrodynamic tethers for removing hazardous objects from the low Earth orbit region.

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

Space debris environment evolutionary model for the geosynchronous Earth orbit region, GEODEEM, developed by Kyushu University was upgraded for better understanding. This paper explain the key features of this upgraded model. One of keys of this upgrade is that all satellites larger than 10 cm in size are tracked individually. The benefits of this upgrade are: 1) collision accidents can be estimated based upon one-by-one collision probabilities, and 2) more realistic scenarios like removing certain objects from orbits can be applied. This paper also present the latest prediction of future space debris environment from 2008 to 2108. The model indicates that explosion is the main debris production mode in next 100 years.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper proposes a strategy to search fragments from breakups in the Geosynchronous Earth Orbit (GEO) region based upon population prediction and motion prediction by means of ground-based optical observations. Breakup fragments have uncertainties in the states such as their position and motion, or even in their existence. Population prediction and motion prediction resolve those uncertainties. Population prediction evaluates the time-averaged distribution of fragments, whose position at a given time is unknown, in the celestial sphere. Motion prediction evaluates the expected motion of fragments appeared in image series acquired by a telescope's CCD camera. This paper logically describes procedures of the search strategy, and provides mathematical expressions of population pre- diction and motion prediction. This paper also validates the search strategy via actual observations, in which a confirmed breakup in the GEO region is selected as a target. It is concluded that the proposed strategy is valid even for searching uncataloged fragments from breakups in the GEO region.

DOI： http://dx.doi.org/10.1016/j.asr.2012.01.012

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

This paper summarizes recent microsatellite impact tests conducted under contract with the NASA Orbital Debris Program Office. The motivation for the impact tests is twofold. First, as new satellite materials continue to be developed, there is a need for impact tests on satellites made of modern materials to better characterize the outcome of future on-orbit satellite fragmentation. Second, it is necessary to extend tests to different velocity regimes to cover potential low-velocity collisions in the geosynchronous region. To date, seven impact tests have been carried out. All microsatellites were totally fragmented and generated more than 1000 fragments each. Fragments down to about 2 mm in size were collected, measured, and analyzed. Main summary of this paper includes size, mass, area-to-mass ratio, and shape distributions of fragments generated from each test and how they vary with size, material type, and impact parameters.

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： http://dx.doi.org/10.1016/j.asr.2011.01.008

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study proposes a motion detection and object tracking technique for GEO debris in a sequence of images. A couple of techniques (called the "stacking method" and "line-identifying technique") were recently proposed to address the same problem. Although these techniques are effective at detecting the debris position and motion in the image sequences, there are some issues concerned with computational load and assumed debris motion. This study derives a method to estimate motion vectors of objects in image sequence and finally detect the debris locations by using a computer vision technique called an optical flow algorithm. The new method detects these parameters in low computational time in a serial manner, which implies that it has an advantage to track not only linear but also nonlinear motion of GEO debris more easily than the previous methods. The feasibility of the proposed methods is validated using real and synthesized image sequences which contain some typical debris motions.

DOI： http://dx.doi.org/10.1016/j.asr.2011.12.010

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（大学，研究機関等紀要）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（大学，研究機関等紀要）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2514/1.11998

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2514/1.11600

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.asr.2003.11.018

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.ijimpeng.2003.09.028

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

Modeling the Orbital Debris Environment

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

Consequences of Continued Grwoth in the GEO and GEO Disposal Orbital Regimes

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2514/2.3786

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

DOI： 10.1016/S0273-1177(01)00398-2

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/S0094-5765(00)00127-2

記述言語：日本語  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/S0273-1177(99)00004-6

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1006/jsvi.1996.0390

記述言語：日本語  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（大学，研究機関等紀要）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

開催年月日： 2024年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：姫路市   国名：日本国  

Solar radiation pressure (SRP) affects spacecraft motion in high-altitude orbits, which depends not only on the satel- lite orbit and attitude but also on its surface optical properties. Metallic surfaces yield anisotropic reflections, and the SRP on such surfaces also represents anisotropy. Considering anistoropic SRP has the difficulty that stems from the fact that anisotropic SRP no longer has an analytical solution and numerical integrations are required. The analytical formulation of anisotropic SRP contributes to the stability analysis and controller design for satellites that exploit SRP. To this end, this paper derives an analytical approximation method to calculate the anisotropic SRP modeled with the Ashikhmin–Shirley model. This paper approximates the anisotropy by using multiple spherical Gaussians. The multi- plication of a spherical Gaussian also results in a spherical Gaussian, and this property enables analytical integration of anisotropic reflections. The approximation accuracy of the anisotropic SRP is numerically verified.

開催年月日： 2024年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

宇宙ゴミの増大を抑制し、また除去を積極的に進めるためには、宇宙企業の活動が不可欠であり、その ためのインセンティブ設計を社会制度として適切に行う必要がある。しかし、現状の不換貨幣システム では課税と助成金・補助金の仕組みをベースとした設計に頼らざるを得ず、現実的な解を得るのに困難 があった。筆者らは過去に新たなデジタル通貨(ADR 通貨)を用いる解を提案しているが、現状の貨幣制度との差から概念が普及しづらいという別の困難がある。そこで本研究では、法定通貨と ADR 通貨が 共存する社会における宇宙企業の企業活動をシリアスゲーム(主目的が娯楽ではないゲーム)としてシミ ュレーションするテキストベースのゲームを生成 AI を用いて開発した。この手法は簡便であり、宇宙 開発に関わる他の様々な諸問題についても、意思決定のシミュレーションに役立つ可能性がある。

開催年月日： 2024年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

本講演は、地球温暖化が宇宙活動の⻑期的持続可能性に与える影響を検証します。地球温暖化による熱 圏寒冷化が、熱圏の大気密度を低下させています。本講演では、大気密度の減少率を仮定し、低軌道宇 宙物体分布の将来推移を評価します。「Reg Launches」，「90%PMD」および「大気密度は低下しない」 をベースラインとします。「Reg Launches」は、過去 8 年間の投入履歴を繰り返すことを意味し、「PMD」 は Post Mission Disposal の略で、「LEO を通過する軌道、または LEO に干渉する可能性のある軌道で 運用フェーズを終了する宇宙機またはロケット上段機体は、予想される残存軌道寿命が 25 年以下の軌 道に移動されるべきである」を意味します。PMD の前の割合は成功確率を表します。講演では、100 年 間の分布増加、100 年後の空間密度および 100 年間の衝突活動などを比較します。

開催年月日： 2024年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

本研究では人工衛星が爆発破砕した場合を対象とした爆発破砕モデルについて検討を行っている.簡易 的な真空容器中にて，CFRP 板と電子部品を含む模擬衛星ならびにアルミニウム板とアルミフレームで 作ったアルミ箱を用いて爆発破砕実験を行っている.爆発源としてはエネルギー推測が可能な PETN 爆 薬を用いている.破砕後の破片回収ならびに高速度撮影結果より，破片寸法，飛散速度を計測し，爆発 破砕モデルを検討している. 本講演では，模擬衛星ならびにアルミ箱を用い，爆発源の位置ならびに質 量を変化させた爆発破砕実験を行い，爆発後の模擬衛星本体の平行速度ならびに回転速度について検討 を行った結果ならびにそれらの発生破砕破片について爆発破砕モデルとの比較を行った結果について 報告する.

開催年月日： 2024年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

サイズ 2 mm 以下の微小デブリをその場計測することで，破砕による環境変化を推定する取組を紹介す る.サイズ 2 mm 以下の微小デブリの環境認識は，宇宙機の防護設計の観点から重要である.そのため， まず微小デブリの環境を適宜更新するための動的環境モデルを紹介する.このモデルは，適応型モンテ カルロフィルタを適用することで衛星破砕による環境変化にも対応できる.また，サイズ 2 mm 以下の 微小デブリの起源を特定することも，破砕による環境変化を推定するために重要である.そのため次に， 非線形最小二乗法を適用することで，微小デブリのその場計測のみで破砕物体を推定できることも紹介 する.加えて，破砕起源の推定手法に一工夫加えることで，2 物体の衝突起源を推定できることも示す.

開催年月日： 2024年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

本発表ではデブリインデックスを用いた軌道許容量の評価手法について最新の研究成果を報告する。 JAXA 研究開発部門では軌道環境への影響を表すデブリインデックスについて研究を行っており、イン デックス制定のために必要な2つのステップ及び、インデックス式を検討した。本研究では質量特性や 空間密度が均一化された軌道環境を用いた数値シミュレーションを行い、提案するインデックス式が評 価物体の持つ破砕の影響を捉えられるか検証する。また初期背景物体の環境を変化させた軌道環境推移 の数値解析を実施し、軌道毎のインデックス合計値と環境推移の傾向の相関性を評価する。軌道許容量 については高度毎に異なる推移傾向を整理し、許容量を論じる上で考慮すべき事項を明らかにする。ま たインデックスで軌道許容量の評価を行う。

開催年月日： 2024年10月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Milan   国名：イタリア共和国  

Active debris removal (ADR) is considered necessary for the stability of the orbital environment because there are already a large number of objects in orbit and it is believed that their number will increase due to mutual collisions. Various studies have been conducted to determine which debris objects should be removed, but the on-orbit environment has changed dramatically in recent years with the addition of large constellations and the occurrence of serious fragmentations. The debris removal targets are not permanent, but must be reviewed according to the situation at any given time. Also, as for the post mission disposal (PMD) for the spacecraft in LEO, it has been considered appropriate and reasonable to de-orbit from the operational orbit into the disposal orbit with orbital lifetime of 25 years or less, but recently there are arguments that it should be shortened to 5 years or even 1 year. It was often considered that ADRs should be conducted to transfer ADR targets to a disposal orbit with orbital lifetime of 25 years, but it is necessary to consider whether the disposal orbit should also be shortened to 5 years or 1 year. There is also a debate as to whether ground safety is acceptable by falling removed large objects to the ground, even though a large number of objects originally re-enter the earth every year and the target objects will re-enter the earth uncontrolled in the future even if not subject to ADR. Therefore, this study discusses ADR targets and mission requirements based on discussions of recent environmental changes and the impact of ground safety. In this study, the debris evolutionary model NEODEEM developed by Kyushu University and JAXA is used to evaluate the effect of removal. First, changes with and without constellation or the altitude of the disposal orbit are discussed. The effects are evaluated for such as the number of objects and collisions, the collision rate, and the number of conjunctions at each altitude calculated with NEODEEM. Debris with high collision rates but low altitudes do not reduce the overall number of objects much after ADR, but the impact for the number of conjunctions for the operational spacecraft will be discussed. Changes in objects falling to the ground with and without ADR are also compared.

開催年月日： 2024年10月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Milan   国名：イタリア共和国  

Relative orbit estimation is a important technique in on-orbit servicing missions not to enlarge the risk of collision. At a far range, the observations are obtained by an optical camera and are unresolved images of the target object, which provide two-dimensional position on a camera image. This observation is also described as two bearing angles, i.e., azimuth and elevation angles from the service satellite to the target. The relative orbit estimation with bearing angles is known as angles-only navigation and has been intensively studied. The difficulty of angles-only navigation stems from the observability of the relative distance. That is, the relative distance norm between the service satellite and the target is weakly observable. Although this difficulty can be avoided by implementing known maneuvers or considering nonlinear motion caused by perturbations, they consume extra fuels or provide a slight improvement of the observability. To enhance the observability, this study fuses the light intensity of the unresolved image, called light curves, with bearing angle observations. The light curves depend on the relative distance between the service satellite and the target, and the data fusion of light curves can compensate for the weakly observability of the relative distance. Light curves include information on not only the target orbit but also the attitude, shape, and optical properties of the target, which are formulated with a bidirectional reflectance distribution function (BRDF). This study uses the Ashikhmin–Shirley model to describe the light curves of the target, because this model can express both isotropic and anisotropic reflection. The BRDF is a highly-nonlinear function of the target state, and the unscented Kalman filter is employed to estimate the relative state of the target. Numerical simulations consider two types of objects: a flat plate and a box-wing satellite, which verify the proposed relative orbit estimation method compared to a conventional angles-only method. Furthermore, two optical properties, i.e., isotropic reflection and anisotropic one of the Ashikhmin–Shirley model, are examined. The simulation results show that the convergence rate of the relative distance is significantly improved by the light curve observations. Fisher information as a quantitative metric is also compared with the conventional method.

開催年月日： 2024年10月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Milan   国名：イタリア共和国  

This paper aims to verify the correlation between the orbital evolution and a debris index and discuss the capacity. The rapid increase in the number of launch traffic due to the growing of space developments raises the possibility of environmental deterioration in orbit and concerns of overloading against a capacity. The deterioration could be generally rephrased as an increase in the number of objects that consequently causes the increase in collision probability or the number of conjunctions. Especially if plenty of non- operational objects are abandoned, the number of collisions with these objects would be raised. The new fragments will cause a rapid increase in the collision probability and the number of conjunctions with nearby operational satellites, immediately after a fragmentation. At higher altitudes, most of the fragments would remain in orbit which keeps the collision probability and the number of conjunctions higher for decades or hundreds. The growth of small debris that is un-trackable from the ground would also be a serious threat to an operational spacecraft. Since these environmental impacts would be changed due to the altitude or evolution period, this study organizes the objective and evaluated terms taking account a capacity. The debris index is an effective tool that can contribute to, for example, the selection of orbits with less environmental impact or the targets of active removal. To realize these objectives, the index should be able to assess how an object affects to environment and how long this risk will persist. The previous paper of this study proposed two processes that should be followed to establish an index. Since the previous study showed the tendency of the proposed index with few numerical simulations, this paper firstly verifies whether the proposed index can evaluate the impacts of fragmentation using a unified background environment, i.e., the mass, area of each object, and the number of objects in each altitude band are the same value. The sensitivity and correlation between the components of the index formula and the orbital environment evolution will be assessed through some numerical simulations using a debris environment evolutionary model. The total index of objects in an altitude band is compared with the trend in the number of objects or collision probability by changing the number of background objects, and the orbital capacity will be discussed. The current environment is also assessed with these above perspectives using the JAXA orbital objects database.

開催年月日： 2024年10月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Prague   国名：チェコ共和国  

開催年月日： 2024年9月

記述言語：日本語   会議種別：口頭発表（招待・特別）  

開催地：北九州市   国名：日本国  

開催年月日： 2024年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Maui, HI   国名：アメリカ合衆国  

開催年月日： 2024年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Busan   国名：大韓民国  

This paper investigates the impact of space debris and global warming on the long-term sustainability of outer space activities. Previous studies have indicated that the thermosphere is becoming increasingly cold due to global warming. As the temperature of the thermosphere decreases, the atmospheric density of the thermosphere also decreases. Based on previous studies, this paper assumes that the rate of decrease in atmospheric density is 2% and 5% per decade since 1971. The baseline scenario uses the initial population as of 1st January 2021 and assumes “Reg Launches” and “90%PMD” with no decrease in atmospheric density. The term “Reg Launches” means repeating the insertion history of the past eight years from 1st January 2013 to 31st December 2020. “PMD” is an acronym for Post Mission Disposal, meaning the guideline that recommends that “Spacecraft or orbital stages that are terminating their operational phases in orbits that pass through the LEO region, or have the potential to interfere with the LEO region, should be de-orbited (direct re-entry is preferred) or where appropriate, maneuvered into an orbit with an expected residual orbital lifetime of 25 years or shorter.” The percentage before PMD represents the probability of success. Comparisons include population growth over 100 years, spatial density after 100 years as a function of altitude, and collision activities over 100 years as a function of altitude. Finally, this paper may conclude that if atmospheric density continues to decrease, the effectiveness of space debris mitigation measures will weaken, and the guidelines may need to be revised to sustain outer space activities.

開催年月日： 2024年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Busan   国名：大韓民国  

Sub-millimeter-size debris still has the potential to break up an operational satellite despite its small size. Nevertheless, it is difficult to observe such tiny debris from the ground and predict orbits accurately, leading to an insufficient environment model of sub-millimeter-size debris. Therefore, a measurement satellite is proposed to detect impacts with sub-millimeter-size debris and record their positions with the time stamp then construct a dynamic environment model. As a preliminary step, this paper introduces a method to estimate two sets of orbital elements, inclination, right ascension of the ascending node, and nodal precession rate, of broken-up objects using position information of detected debris produced by collision. Previous studies have shown it is possible to estimate orbital elements in case of an explosion caused by one object by determining the appropriate initial values and using the iteratively reweighted least square method. For collision, the initial values cannot be found in the same method as previous studies because which object detected debris originated from cannot be known. This paper uses the Lomb-Scargle periodogram, frequency analysis for unequally spaced data to avoid this problem. This approach allows us to find the initial values of the nodal precession rate of two objects without prior separation of the detected data into two, followed by inclination and right ascension of the ascending node by applying the nodal precession rate of J2 perturbation and constraint equation. Furthermore, weighting each plot in the least square method reduces the influence of one of the objects not subject to estimation. In this way, two sets of orbital elements are estimated.

開催年月日： 2024年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Busan   国名：大韓民国  

This paper investigates the fragmentation of the Russian EKRAN 2 spacecraft (International Designator 1977-092A) using three different approaches, which exploded due to dead batteries in June 1978. First, this paper reviews the longitudinal perturbation of fragments from the EKRAN2 spacecraft and hypothesizes that gas and fragments from dead batteries placed outside may have pushed the main body to release appendages such as solar array paddles and phased array antennas. Second, this paper conducts two explosive fragmentation experiments using two identical mock-up satellites. One has a PETN explosive inside the main body, whereas another has the same explosive outside the main body. When the PETN explosive was inside the main body, the mock-up satellite was completely fragmented to release many fragments. When the PETN explosive was outside the main body, on the other hand, only a hole was made on the exterior wall where the PETN explosive was placed to release only fewer small fragments. This fact supports the hypothesis derived from the analysis of the longitudinal perturbation of fragments. Finally, this paper conducts optical measurements of fragments from the EKRAN 2 spacecraft and finds that the light intensity changes at a relatively short period. It is also found that among the EKRAN series spacecraft, some change their light intensity over a relatively short period like fragments from the EKRAN 2 spacecraft, while others do not.

開催年月日： 2023年12月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：長崎県長崎市   国名：日本国  

This paper investigates traklets observed by the Pegasus Observatory at Kyushu University, Fukuoka. First, this paper associates the tracklets with a fragment from the on-orbit fragmentation of the Russian EKRAN 2 spacecraft by using a Plate Solving method. Second, since the light intensity along the tracklets change significantly over a short exposure time, this paper concludes the possibility that the fragment may be rotating rapidly.

開催年月日： 2023年12月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：長崎県長崎市   国名：日本国  

This paper evaluates efficiency of an observation plan for a group of fragmentation debris generated from specific breakup events in low-earth orbit. In this work, space objects detected by an atmospheric radar system called EISCAT Svalbard Radar (ESR) are treated. After consideration of propagation errors utilizing orbital elements in a two- line element set (TLE) including various epochs, an effectiveness of the planning method based on observation directions with high density of propagated orbits of the fragmentation debris is described. Results from a correlation analysis for the observation data obtained from a campaign in 2019 finally verifies practical effectiveness of the proposed planning method.

開催年月日： 2023年12月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：長崎県長崎市   国名：日本国  

This paper verifies whether some orbital parameters of on–orbit satellite fragmentations can be estimated from in–situ debris measurements conducted in elliptic orbits passing through a given altitude range. Previous studies have verified that some orbital parameters of a broken–up object in a circular orbit can be identified when in–situ debris measurement were conducted in circular orbits. For this study, in–situ debris measurements are assumed to be conducted in two elliptical orbits passing through altitudes of 600 km to 800 km and 800 km to 1000 km.

開催年月日： 2023年12月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Sugar Land, TX   国名：アメリカ合衆国  

This study evaluated the environmental impacts of orbital fragmentation such as an anti-satellite test, collision between two objects, and explosion. A debris environment evolutionary model named NEODEEM, jointly developed by Kyushu University and JAXA, was used to predict future populations and calculate collision probabilities after a fragmentation. This study focused on characteristics of the fragmented objects, such as altitude, mass, and whether they belong to a Large Constellation (LC). When a fragmentation occurs in higher altitudes, the new fragments will remain in orbit for a long time. Due to this accumulation, the fragments will not only keep the number of objects and probability of collision higher but also cause the risk of secondary collisions between fragments and background objects. When a collision occurs inside an LC at a lower altitude, the impacts will be short-term because most of fragments decay quickly. However, the number of conjunctions, i.e., operational roads, will increase rapidly because many satellites are operated at the same altitude. This study also discussed a collision probability to an LC taking into account the small size of fragments larger than 1 cm.

開催年月日： 2023年12月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Sugar Land, TX   国名：アメリカ合衆国  

This paper proposes less fuel strategies for space debris removal. To mitigate the risk of space debris cost-efficiently, multi-rendezvous missions are under development. On the other hand, multi-rendezvous missions often require changing orbital planes of removal satellites, which requires a huge amount of ΔV. Therefore, this study focuses on exploiting the J2 perturbation force as an auxiliary force and aims to establish maneuver rules that minimize ΔV consumption while maximizing the benefit of the J2 perturbation. The J2 perturbation equation is explored analytically, which clarifies whether the change in the semi-major axis or the inclination dominates the efficiency of the exploitation. A straightforward criterion is extracted which determines the efficient maneuver based on the initial inclination of the satellite.

開催年月日： 2023年12月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Sugar Land, TX   国名：アメリカ合衆国  

This paper proposes an attitude control method to remove uncooperative spacecraft by laser ablation. To efficiently deorbit space debris using laser ablation, it is necessary to control the attitude motion of the target in advance. A previous attitude controller empirically determines control gains and is easily affected by assumed preconditions. To address this issue, this study proposes an improved attitude control law using laser ablation. By analogy with a magnetic attitude control law, theoretical conditions for designing the control gains are obtained. Numerical examples using the proposed control law are conducted to control the attitude from a random initial rotation of 1 rpm to an arbitrary attitude, which verify the effectiveness of the proposed method.

開催年月日： 2023年12月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Sugar Land, TX   国名：アメリカ合衆国  

This study proposes a relative orbit control law in the laser debris removal method considering the uncertainties of laser ablation and atmospheric drag. A removal spacecraft irradiates laser pulses to a target debris to generate the ablation force for deorbiting. The deorbiting force lowers the target, and the removal spacecraft follows it to maintain its relative position for continuous laser irradiation. In this mission, the difficulty stems from the uncertainties of the magnitude of laser ablation and external disturbances such as atmospheric drag. To tackle this problem, this study derives an adaptive control method using the Gaussian process in which the non-parametric model of the Gaussian process can cancel the uncertainties. Numerical simulations verify the proposed control law under the uncertainties. The proposed control law can contribute to the realization of safer and more secure mission not only for laser debris removal method but also for other debris removal methods and on-orbit services.

開催年月日： 2023年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：富山市   国名：日本国  

This paper proposes a design method for a constellation of satellites. Aiming at improving the prediction accuracy of meteorological disasters (e.g., typhoons, linear rainbands, etc.), observation missions using a constellation of satellites, targeting the East Asian region including Japan have been proposed. An ultra-low orbit is desired from the viewpoint of resolution and weight of the observation equipment, but in general, the swash width from an ultra-low orbit is narrow and it is difficult to observe a specific area at a high frequency. Therefore, this paper proposes the design of a constellation that can observe a specific area with high frequency even with a small satellite in an ultra-low earth orbit.

開催年月日： 2023年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：富山市   国名：日本国  

This paper proposes an attitude control method of an uncooperative spacecraft using lasers. The attitude motion of the spacecraft must be controlled in advance for space debris removal by laser ablation. The control gain in a conven- tional attitude control law is empirically given and is sensitive to assumed preconditions. Thus, this paper improves the conventional attitude control law by providing a method to theoretically obtain the control gain by setting a reference torque based on the angular momentum error. Numerical simulations verify the effectiveness of the control gain designed and robustness against gravity gradient torques and solar radiation pressure torques.

開催年月日： 2023年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：富山市   国名：日本国  

This study proposes a nonparametric regression model to describe the attitude motion of space objects. Understand- ing the attitude of space objects is crucial for accurate orbit propagation. Light curve inversion is known as one of the methods of space objects ’attitude inference. However, previous studies have assumed known shapes for the estimation. Thus, this paper constructs nonparametric attitude and light curve models without shape information using Gaussian process regression. The shape of space objects is implicitly learned from the attitude differences that stem from dis- turbance torques, i.e., solar radiation pressure torques in this paper. Numerical examples include three types of object shape and evaluate the regression models.

開催年月日： 2023年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：富山市   国名：日本国  

This paper proposes a close approach analysis method considering the attitude motion of two colliding objects. De- tailed close approach analysis is important because the number of space objects has been increasing in recent years. Conventional conjunction assessments assume two colliding objects to be point masses with no volume, but they are ob- jects with volume. In the proposed method in this paper, the first step calculates the time of close approach considering two objects as point masses. Next step chooses two poses (i.e., attitude and position) when the distance becomes less than a given threshold, and the third step interpolates the two poses using dual quaternions. Dual quaternions can de- scribe the translational and rotational motions, which ensures the uniquness of the interpolation. Numerical simulations are conducted to verify the proposed method and compre it with a conventional method.

開催年月日： 2023年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：富山市   国名：日本国  

This paper proposes a method to classify LEO objects detected via EISCAT radar, based on orbital characteristics of the fragmentation debris　originated from different breakup events. Since many of the detected objects can be identified with the known cataloged objects, most of them can also be classified as one of the groups of debris correlated to specific breakup events. In this paper, aided by a concept of Admissible Region, a classification method for the radar observation objects in　LEO is derived and applied to results of an observation campaign in 2022.

開催年月日： 2023年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：富山市   国名：日本国  

This paper solves a singular problem to stabilize a space-advertisement formation. The space advertisement is a dot　matrix illuminating in the night sky seen from the ground. Using multiple satellites with light sources, the arbitrary dot matrix can be made by considering relative apparent position of each dot from a representative dot. This study solves a singular problem of a coordinate system which describes the positions of the dots to finally stabilize the dot matrix. This study introduces a new topocentric coordinate system to solve the singular problem and formulates the relative apparent position of the dot as linear functions. The formulation generally describes the relative apparent position of satellites seen from the ground. The proposed formulation reveals a stability of the dot matrix as well as solving the singular problem. The stability of the dot matrix is decomposable into six coefficients related to a set of relative orbital elements. Considering the characteristics of the six coefficients, a stable condition is revealed. Even with semi-major axis difference, the dot matrix can be stabilized during a visible span.

開催年月日： 2023年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：富山市   国名：日本国  

This study proposes the relative orbit control law considering uncertainties of disturbance force. The relative orbit　control of a spacecraft about non-cooperative objects is an promising technology for future on-orbit servicing and debris removal missions. The uncertainties of disturbance force may increase the relative position error, resulting in a high risk of collision. To tackle this problem, this study derives an adaptive control method using Gaussian process. Gaussian process is a data-driven machine learning model and is suitable for function regression problems. Furthermore, Gaussian process can learn non-parametric models and cancel the uncertainties in control architecture. Numerical simulations verify the proposed control law under differential drag.

開催年月日： 2023年10月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Baku   国名：アゼルバイジャン共和国  

This paper examines the effect of shortening the post-mission disposal lifetime, i.e., changing the so- called 25-year rule to 5-year rule. Using NEODEEM, debris evolutionary model developed by Kyushu University and JAXA, we evaluated the change in the on-orbit environment at each altitude in terms of long-term stability and short-term safety such as the number of collision avoidance maneuvers and the collision rate. When evaluated in terms of the long-term total effective number of on-orbit objects, the 25-year rule is sufficiently effective and has been adopted in consideration of the balance with the V required for orbit transfer. However, it is not appropriate to evaluate only by the effective number of objects. For example, the greater the effective number in the low orbit in the initial state, the fewer the overall number appears to increase due to the cancellation of the effect of their decay from the lower altitude and their tendency to increase at high altitude, but in reality, the situation is different at each altitude. Thus, it is necessary to evaluate not only the effective number of objects but also the collision rate, etc. at each altitude in order to assess long-term stability. In addition, if the number of launches increases beyond what has been assumed, it would be necessary to evaluate its impact. It is shown the collision rate at an altitude of around 600 km will increase if the number of launches to high altitude and the PMD compliance rate increases, although the impact of collision is not long term. In the short term, the 5-year rule reduces the collision rate and collision avoidance frequency at an altitude around 600 km more than the 25-year rule. Similarly, if the number of spacecraft descending to an altitude of around 500 km increases due to the 5-year rule, the collision rate and the expected number of collision avoidance maneuvers for the ISS, for example, will increase in the very short term. However, if the 5-year rule is not applied instead of the 25-year rule, and subsequent collisions occur at altitudes around 600 km, the collision rate and expected number of collision avoidance maneuvers will increase later because the fragments fall to a lower altitude. This suggests that the post mission disposal lifetime should be set according to the number and size of objects launched.

開催年月日： 2023年10月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Baku   国名：アゼルバイジャン共和国  

Space debris index is a measure to assesses the environmental impacts of a spacecraft or a mission, and there have been many studies and controversies on its utilization and formulation. Especially, the index formulation is a topic that has many productive studies to accurately represent the impact of the target object or mission on the orbital environment. It is estimated that the higher the value of the index calculated based on the mass of the spacecraft or mission orbit, the greater the impact of the index. However, it is not clear whether a 10-fold increase in the index value will result in a 10-fold deterioration of the environment. Therefore, it is necessary to establish some criteria for evaluating the effect of the index; what changes are good or bad for the orbital environment. This paper discusses the steps which should be taken to establish debris indices that can be widely and easily used by operator, companies, and other stakeholders. These steps are divided into two categories, definitions of criteria and formulations of debris indices. By providing the criteria, the relationship between the value of index and environmental impacts of spacecraft or missions would be revealed. Such criteria also would compare the effects of different indices from the same perspective. Moreover, some specific thresholds of the index could be set taking into accounts orbital capacity. This paper discusses which criteria, such as effective numbers of objects, a collision probability, and a number of conjunctions that are generally used to show the environmental predictions, are suitable for understanding the effects of debris indices. The formulations of space debris indices are also important for widely and easily uses of indices. Currently, some organizations which have debris environment evolutionary models assess spacecraft or mission’s environmental impacts using their models. If debris indices are defined by simple components such as spacecraft’s mass, orbital lifetime, and collision probability, indices assessments would be easily conducted without using debris evolutionary model. In order to formulate such simple index, comparison of indices effects through evaluation of debris evolutionary models is needed. This paper proposes some indices that can be evaluated using evolutionary model, and assesses their short/long-term impacts by criteria proposed in this study. This paper also proposes the indices defined by simple components, and assesses whether the formulas are essentially the same evaluation with indices which use evolutionary model.

開催年月日： 2023年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Kurume-Fukuoka   国名：日本国  

This paper investigates the on-orbit satellite fragmentation of the Russian EKRAN 2 spacecraft, which exploded due to dead batteries in June 1978. This paper reviews the longitudinal perturbation of fragments and hypothesizes that gas and fragments from dead batteries placed outside may push the main body to release appendages such as solar array paddles. To verify this hypothesis, therefore, this paper conducts two explosive fragmentation experiments using two identical mock-up satellites. One has a PETN explosive inside the main body, whereas another has the same explosive outside the main body. When the PETN explosive was inside the main body, the mock-up satellite was completely fragmented to release many fragments. If the PETN explosive was outside the main body, on the other hand, only a hole was made on the exterior wall where the PETN explosive was placed to release only fewer small fragments. Therefore, this paper concludes that gas and fragments from dead batteries placed outside pushed the main body to release appendages.

開催年月日： 2023年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Kurume-Fukuoka   国名：日本国  

This paper briefly introduces the update of NEODEEM the Near-earth Orbit Debris Environmental Evolution Model. NEODEEM was jointly developed by Kyushu University and JAXA to track near-earth space objects. NEODEEM has contributed to the worldwide effort not only to predict the future space debris population but also as an indispensable tool to identify effective measures for space debris mitigation and environmental remediation. The update introduced in this paper includes its orbit propagation and collision probability evaluation algorithm.

開催年月日： 2022年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

This paper briefly introduces a new approach to estimating some orbital parameters of on-orbit satellite fragmentations (precisely, the direction of angular momentum at a specific time and its time change) from in-situ debris measurements. Previous studies have applied a nonlinear least-squares fitting to a constraint equation derived from the fact that a piece of debris detected shares the geocentric position vector with an in-situ debris measurement satellite. However, the new approach applies a nonlinear least-squares fitting to the history of geocentric declination at the detection time. The previous studies have been verified under ideal conditions where all detections are assumed to be at the intersection of the two orbital planes of a broken-up object and an in-situ debris measurement satellite. However, this study verifies using more realistic measurements from a close approach analysis.

開催年月日： 2022年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

To remediate the orbital environment, active debris removal (ADR) from low Earth orbit is required. Laser ablation is a vital technology for contactless active debris removal, where a service satellite irradiates laser pulses to a target satellite to generate the ablation force for deorbiting. Since the ADR method using a laser requires no deorbiting device to attach, the ADR by laser enables simultaneously deorbiting multi-targets, which is a promising ADR technology. As a preliminary study of multi-deorbit, this paper designs the formation with respect to multi-targets to maximize the laser duration or minimize collision probability. Furthermore, the laser system has significant constraints such as laser focal length, laser irradiating angle, and camera angle. Thus, the designed formations must satisfy the constraints of the laser system. To this end, two formations that require attitude control or no attitude control are proposed. Their performances are compared in terms of safety and deorbit efficiency.

開催年月日： 2022年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

As the number of spacecraft and orbital debris is rapidly increasing, Active Debris Removal is becoming an essential technology to maintain a sustainable space environment. SKY Perfect JSAT and RIKEN are developing a laser-equipped ADR satellite that adopts laser ablation technology to generate a thrusting force on the target object. This ADR method does not require any physical contact with the target object, which is a remarkable characteristic compared to the widely proposed methods. The laser satellite can perform detumbling and deorbiting of the target object as long as its relative distance is within the laser range. For that reason, docking or capturing is no longer needed for this ADR method. On the other hand, proximity operations need to be considered over the entire mission period. ADR mission provided by Laser satellite can be divided into several phases, such as detumbling phase and deorbiting phase, and each phase requires individual orbit design. This presentation will show the concept of the orbital design for each mission phase and provides the validation results by using Hill coordinate systems and relative orbital elements.

開催年月日： 2022年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

This presentation describes the status of the Space Debris Index study by the debris modeling team of JAXA's Research and Development Directorate. The debris index which indicates the environmental impact of spacecraft or missions has been the subject of international discussion and research. The modeling team organized the definitions and applications of the debris index and summarized which characteristics of the environmental impact of spacecraft should be evaluated. From this result, we narrowed down the features to be considered, and are working on an index formulation. The index is formulated in terms of short-term and long-term effects on the orbital environment. The environmental evaluation criteria are also discussed to confirm that the index values correctly represent the impact of spacecraft on the orbital environment. This presentation also shows the effect of environmental improvement using the debris index. The objects in the orbit are evaluated based on several indices, and the top 50 objects are removed from the orbit.

開催年月日： 2022年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

There is a growing concern about climate change caused by greenhouse gases. Especially, carbon dioxide has significant influences not only on the lower atmosphere but also on the upper atmosphere such as the thermosphere where space objects are orbiting. One of the problems of increasing carbon dioxide is that it reduces the density of the thermosphere, resulting in a less atmospheric drag on space objects. This paper evaluates the long-term influence of decreasing the atmospheric drag on the space environment and space activities using an orbital debris evolutionary model. In this study, Jacchia-Roberts 1971 atmospheric model is used to calculate the atmospheric density. In addition, this study makes corrections to atmospheric density with considering the long-term density decrease. This paper also reveals the long-term impact of density decrease on space activity by calculating the debris number transition, the extension of debris orbital lifetime, and collision probability with debris. Furthermore, this study shows the change of delta-v and the collision probability with other objects to satisfy the 25-year rule.

開催年月日： 2022年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

JAXA has been evaluating the future space debris environment using a debris evolutionary model named NEODEEM, developed in collaboration with Kyushu University. This evolutionary model is able to generate orbital debris generated by on-orbit collisions and explosions, and also to estimate and evaluate the impact of debris on the long-time orbital environment. In addition, by using this model, ASAT events also may simulate and evaluate, which has become a problem in recent years, can also be simulated. In this presentation, various analysis examples based on this evolutionary model are introduced.

開催年月日： 2022年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

The Breakup model includes cases of collisions and explosions, and this study examines the breakup model for satellite explosions. Explosive fragmentation experiments were conducted using a mock-up satellite in a simple vacuum vessel. Then, the fragment size and typical velocity are measured using the high-speed photographing results and recovered fragments after the experiment, and an explosion breakup model is examined. A PETN explosive has predictable explosive energy and is used as the explosion source. This presentation compares the results obtained by changing the location of the explosion source inside and outside the mock-up satellite. Then, the effect of the location of the explosion source on the broken condition and the breakup model is examined. And It is reported that different results were obtained depending on the location of the explosion source. In addition, the situation of Ekran2 and its fragments was examined as a case of a breakup. As a result, the source of the explosion may be outside.

開催年月日： 2022年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：オンライン   国名：日本国  

This paper investigates on-orbit satellite fragmentations in the geostationary region. First, this paper reviews the on-orbit fragmentation of a US TITAN 3C TRANSTAGE based on a previous study and indicates that it was a relatively major fragmentation. Second, this paper reviews the on-orbit fragmentation of the Russian EKRAN 2 spacecraft based on longitudinal perturbation and indicates that it was a relatively minor fragmentation. Finally, this paper concludes that the gas and fragments generated by the burst of batteries placed outside pushed the main body to release appendages such as solar array paddles.

開催年月日： 2022年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：オンライン   国名：日本国  

The space-advertisement mission gives an artificial constellation in the night sky using a satellite formation with light sources. The formation shape observed from the ground which was not discussed by previous studies is revealed. A proper design of satellites using present equations makes an arbitrary advertisement shape. Moreover, some stable orbits whose advertisement shape can be kept during the visible span are revealed, which makes a stable advertisement design without control.

開催年月日： 2022年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：オンライン   国名：日本国  

This paper describes an analysis of radar observation data detecting space objects in low-earth orbit (LEO), which are correlated to cataloged ones. In this work, the objects detected by an atmospheric radar system called EISCAT Svalbard Radar (ESR) are treated. During the observation campaign in March of 2022 (total 14 hours for two days), about 7 hundred hard targets were detected through the radar facility. This paper shows the results of a correlation analysis between the detected objects and known and tracked ones, or so-called cataloged objects, and discusses them from a viewpoint of identification for space debris generated via collisions and explosions in orbit.

開催年月日： 2022年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：オンライン   国名：日本国  

A fragmentation model representing the situation at the time of generation is necessary for the prediction of the space debris environment. Explosive fragmentation is one of the causes of space debris generation. Explosive fragmentation produces more space debris. Therefore, in this study, an explosion fragmentation experiment using a small mock-up satellite was performed. A PETN explosive installed inside the small mock-up satellite was used as the explosion source. The fragments were collected and photographed with a high-speed camera. This paper reports the results obtained by examining the difference in internal explosive energy and the results obtained with the NASA standard break-up model.

開催年月日： 2022年11月

記述言語：日本語  

開催地：熊本県熊本市   国名：日本国  

This paper briefly introduces a new approach to estimate some orbital parameters of on-orbit satellite fragmentations (specifically, the direction of angular momentum at a specific time and its time change) from in-situ debris measurements. Previous studies have applied a nonlinear least-square method to a constraint equation derived from the fact that a piece of debris detected shares the geocentric position vector with an in-situ debris measurement satellite. However, the new approach applies a nonlinear model fit to the history of geocentric declination at the time of detection. This paper also verifies that the new approach works effectively under ideal conditions where all detections are assumed to be at the line of intersection of the two orbital planes of a broken-up object and an in-situ debris measurement satellite.

開催年月日： 2022年11月

記述言語：日本語  

開催地：熊本県熊本市   国名：日本国  

This paper provides experiment results of a satellite fragmentation due to battery. The current explosion model in the NASA standard breakup model is based on the outcome of rocket upper stage explosions. The NASA breakup model may not be able to describe the physical properties of fragments from satellite battery-induced explosions, however. Therefore, this study conducts satellite battery-induced explosions using mock-up satellites. To simplify the experiment, an 1 g of PETN explosives were used instead of batteries. The explosion experiments were filmed by a high-speed video camera. The delta-velocity of the fragments were obtained from these images. The target satellite was completely fragmented after the experiments. Approximately 40,000 fragments were collected. Each fragment was measured and analyzed based on the methods proposed in the NASA standard breakup model. The size, average cross-sectional area, area-to-mass ratio, and delta-velocity distributions were compared with the NASA standard breakup model.

開催年月日： 2022年11月

記述言語：日本語  

開催地：熊本県熊本市   国名：日本国  

On-orbit servicing, where a service satellite performs missions such as life-extension or deorbit of a target satellite, has been planned by many commercial entities. Relative pose estimation (i.e., attitude and orbit estimation) is essential to conduct on-orbit servicing missions successfully because the target satellite is noncooperative in many practical cases. This paper proposes a satellite pose estimation method that allows us to conduct a more accurate and efficient estima- tion using the unscented Kalman filter (UKF). There is a significant advantage in estimating both attitude and orbit motion simultaneously because they are coulle in general. To this end, the unified parameterization of both attitude and orbit using dual quaternions is applied in this paper. Employing the dual quaternions in the UKF, however, has a difficulty that stems from the algebraic constraints of the dual quaternions. That is, the algebraic constraints of dual quaternions are violated when calculating the weight-mean dual quaternion in the UKF sequence. This paper proposes and compares the following two methods to compute the averaged dual quaternion: 1) dual quaternion linear blending and 2) dual quaternion averaging. These two methods allow us to calculate the weight-mean dual quaternions while keeping the algebraic constraints. Numerical examples for relative pose estimation are conducted to discuss the accuracy and effectiveness of the proposed methods.

開催年月日： 2022年11月

記述言語：日本語  

開催地：熊本県熊本市   国名：日本国  

This paper proposes a control law for simultaneous deorbit using laser ablation. Laser ablation is a vital technology for contactless active debris removal, where a service satellite with a laser system irradiates a target satellite to generate the ablation force for deorbiting. The deorbiting force decelerates the target, and the service satellite must maintain its relative position and continue irradiating. The difficulty of simultaneous deorbiting stems from the relative motion between the service satellite and the target in powered flight because conventional formation flying missions assume that only a service satellite maneuvers. This paper derives the relative equations of motion between the service satellite and the target in powered flight. A control law for the simultaneous deorbit is proposed, which determines the timing and direction of the laser ablation and the electrical thrust so that the formation periodically returns to the desired formation. Numerical simulations are performed for two test cases to verify the control law involving the uncertainties of thrust magnitude.

開催年月日： 2022年11月

記述言語：日本語  

開催地：熊本県熊本市   国名：日本国  

Solar radiation pressure (SRP) is a major disturbance for a spacecraft operated in deep space missions, affecting its orbit and attitude, and high accuracy of SRP calculation is required. SRP calculations are affected by the shape and surface characteristics of the satellite. However, existing computational models do not sufficiently take into account the exact reflective properties of the satellite surface. A detailed reflection model and considering the optical characteristics yield a different SRP and its torque from the conventional ones, resulting in a different attitude motion. In this study, an SRP calculation method that considers exact reflective properties is applied to investigate attitude dynamics using high-fidelity SRP.

開催年月日： 2022年11月

記述言語：日本語  

開催地：熊本県熊本市   国名：日本国  

Low-energy transition orbits in the Earth-Moon three-body problem are known to be chaotic in nature, hence orbit prediction and design are difficult. In this study, in order to predict chaotic behavior, a new method is proposed to approximate high-dimensional chaotic transition trajectories as maps of low-dimensional periapsis maps by dynamic mode decomposition, which is a data-driven approach. Moreover, comparing the approximation errors caused by this method with the dynamical structure of the circle-restricted three-body problem, it is found that orbits with large approximation error are on the boundary of the dynamical structure, therefore the proposed method also leads to the clarification of the dynamical structure of the chaotic orbits.

開催年月日： 2022年11月

記述言語：日本語  

開催地：熊本県熊本市   国名：日本国  

This paper mainly investigates potentials of the “Tomo-e Gozen” system on 1.05 m Kiso Schmidt telescope to be a significant tool for searching missing space debris towards a sustainable space activity. The system is featured by its wide-field and high-cadence videos observations with mosaic CMOS sensors. This paper conducts the investigation through comparing the Tomo-e Gozen's observation data of breakup-originated debris and an observation path based on prediction of the debris population. That work made it clear that the system is useful enough for searching missing space debris. It is also recognized that a long-term observation is needed to complete the task. As well as those results, plotting observation data of uncorrelated target (UCT) objects on a celestial sphere, we confirmed path-like curves which maybe lead to tracking the UCT objects.

開催年月日： 2022年11月

記述言語：日本語  

開催地：熊本県熊本市   国名：日本国  

There is a growing concern about climate change caused by greenhouse gases. Especially, carbon dioxide has significant influences not only on the lower atmosphere but also on the upper atmosphere such as the thermosphere where space objects are orbiting. One of the problems of increasing carbon dioxide is that it reduces the density of the thermosphere, resulting in less drag on space objects. This paper evaluates the influence of decreasing the air drag by an orbital debris evolutionary model. In this study, the motion of space objects is calculated by considering the reduction of atmospheric density in the Jacchia-Roberts 1971 atmospheric model.

開催年月日： 2022年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Paris   国名：フランス共和国  

Because of its large number of satellites, a large constellation (an LC) greatly affects other objects in LEO. Several studies reveal the impact of an LC in LEO missions in various operational scenarios. This study evaluated the environmental impact of an LC explosion in the short- and long-term using the Near-Earth Orbital Debris Environment Evolutionary Model (NEODEEM). Although setting mission scenarios and analysis conditions is important in LC simulations, it is difficult to consider all operational scenarios due to the many combinations. Therefore, this study conducted impact assessments of explosions in an LC, concentrating on the number of explosions, orbital altitude, and scaling factor of the explosions. The results indicated that it is not enough for LC to comply with the current requirement of probability of accidental explosions which is less than 0.001 during the operation. This is because, if the rate is applied directly to an LC with thousands of satellites, continuous explosions (i.e., several satellites explode every year) will occur during the duration of LC. The paper also discusses the behavior of fragments from explosions at different altitudes. The explosions at low altitudes have no significant impact in the long term, although it can cause an incremental change in collision risk in the short term. Similarly, the explosions at high altitudes, such as 1,250 km, have only slightly increments of the expected number of collisions, but its impact could last for over 100 years. The probability of explosions of an LC must be carefully determined through a series of simulations based on the number of satellites and the operational orbit of an LC. This paper also discusses what should be considered in future LC design and operations regarding explosion prevention.

開催年月日： 2022年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Paris   国名：フランス共和国  

Space-advertisement is getting closer with advances in satellite formation flying, which displays an artificial constellation in the night sky. The formation shape composed of pixels of satellites equipping light sources is observed from the ground and is different from formation in relative orbits. For realizing the advertisement shape of high quality, there are two requirements, placing the pixels of the advertisement shape properly and keeping the shape during a visible span. It is not enough to satisfy the requirements of the usual coordinate systems and equations. Considering a topocentric coordinate system, the new transforming equations are derived so that an arbitrary advertisement shape is designed at the target time. Also, stable orbits that keep the formation shape without control are found and an example of stable orbits is presented.

開催年月日： 2022年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Paris   国名：フランス共和国  

Solar radiation pressure (SRP) is a major disturbance for a spacecraft operated in deep space missions, affecting its orbit and attitude, and high accuracy of the SRP calculation is required. The accuracy of SRP calculation is affected by the shape and surface characteristics of the satellite. However, existing computational models do not sufficiently take into account the exact reflective properties of the satellite surface. A detailed reflection model and considering the optical characteristics yield a different SRP and its torque from the conventional ones, resulting in a different attitude motion. In this study, an SRP calculation method that considers the exact reflective properties is applied to investigate the attitude dynamics.

開催年月日： 2022年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Paris   国名：フランス共和国  

Collisions and explosions of satellites generate a large amount of sub-millimeter-size debris, which can cause fatal damage to a spacecraft. However, such tiny debris cannot be tracked from the ground. Therefore, an in-situ debris measurement satellite, which can detect impacts with sub-millimeter-size debris, has been proposed. Based on this concept, previous studies proposed the method to estimate some orbital parameters of the broken-up object. In those studies, it is assumed that the measurement satellite detects impacts at the intersection of the orbital planes of the measurement satellite and the broken-up object. However, simulated measurement data includes fragments contrary to this assumption. Thus, this study introduces a new approach to estimating the orbital parameters of the broken-up object from simulated measurement data. In this study, the inclination, the right ascension of the ascending node, and the nodal precession rate are estimated from the history of geocentric declination using the iteratively reweighted non- linear least square method.

開催年月日： 2022年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Paris   国名：フランス共和国  

Laser ablation is a vital technology for contactless active debris removal, where a service satellite with a laser system irradiates laser pulses to a target satellite to generate the ablation force for deorbiting. The deorbiting force decelerates the target, and the service satellite needs to maintain its relative position and keep irradiating. In other words, both the service satellite and the target are supposed to be deorbited simultaneously, where both satellites have accelerations. The difficulty of simultaneous deorbiting stems from the relative motion between the service satellite and the target in powered flight because conventional formation flying missions assume that only a service satellite maneuvers. This paper derives the relative equations of motion between the service satellite and the target in powered flight. A control law for the simultaneous deorbit is proposed, which determines the timing and direction of the laser ablation and the electrical thrust so that the formation periodically returns to the desired formation. Numerical simulations are performed for two test cases to verify the control law under the uncertainties of thrust magnitude and orbital perturbation.

開催年月日： 2022年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Paris   国名：フランス共和国  

The 21st century is marked by the unprecedented progress of human knowledge in space, quantum mechanics, and machine learning. This progress has in turn lead to a significant increase in satellite launches, with various organizations developing mega-constellations in space to provide new business opportunities. While current predictions estimate that space in Low Earth Orbit will be overcrowded in the future, and sustainability of space will become a critical question as the estimated traffic of 89,000 satellites will be launched by the year 2035. To allow sustainable development of space, especially in Low Earth Orbit, there is a need to develop accurate traffic management and active debris removal mission planning. Lately, several organizations proposed and completed space demonstration experiments for debris removal. Current their designs are part of an ongoing project to develop contact- based debris removal technology. However, this technology poses several problems for satellite removal. We propose a complementary method based on a laser system. The laser is capable to operate from a safe distance by stopping the continuous rotation (detumbling) of space objects. In this paper, we present a case study using the ENVISAT satellite. ENVISAT is an 8,211 kg satellite, launched by European Space Agency. Since 2012, communication has stopped, and it is no longer operational. It is predicted to self-deorbit in the next 150 years. However, the orbital simulation of existing objects found two cataloged space debris which will pass within 200 m., resulting in a close approach every year. The elevated mass of the satellite and the number of close approaches, therefore, pose a considerable threat, leading to the production of debris. SKY Perfect JSAT Corporation is working jointly with Japanese institutions to collaboratively develop laser satellites to stop detumbling and the careful removal of debris. The demonstration mission will be launched by the year 2026-2027. With this case study, a laser-based contactless method can be practiced for removing mega debris like ENVISAT from the Low Earth Orbit.

開催年月日： 2022年2月 - 2022年3月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Beppu-Oita   国名：日本国  

This study proposes a method of classification prior to identification of space debris fragmented in a low earth orbit, which are detected through a ground-based observation. The proposed method is incorporated by a concept of Admissible Region, which can give a reasonable region of unknown two-dimensional parameters such as time-derivative of declination and right ascension for an observational direction. As the two unknown parameters are necessary to estimate orbital elements from observation data obtained through a radar system or a telescope, a method to find their existence region leads to effectively classify the radar observation data based on their orbital elements. The classification method derived in this study is finally verified using results of a correlation analysis between cataloged fragmentation debris and observation data obtained in a campaign at EISCAT Svalbard Radar in 2020.

開催年月日： 2022年2月 - 2022年3月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Beppu-Oita   国名：日本国  

Because of the expansion of outer space activities, space debris is increasing considerably. To sustain the outer space activities, it is necessary to inhibit the generation and increase of space debris by active debris removal. By evaluating “timeliness”, this study determines the space debris to be removed which is a significant issue to improve the orbital environment efficiently. Then, the aims of this study are 1) proposing new evaluation indices considering dangerousness and timeliness and 2) discussing the effects of the indices on future environmental improvement. First, by focusing on the origins of space debris in the future orbital environment from the results of future projections, the necessary factors for the evaluation index are examined. Second, by applying the ridge regression model, the weighting of each factor is evaluated and then new evaluation indices are proposed. Finally, by discussing the future orbital environment following the removals of the objects selected by new evaluation indices, these indices have great effects for future environmental improvement.

開催年月日： 2022年2月 - 2022年3月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Beppu-Oita   国名：日本国  

The effects of GTO debris to LEO environment are revealed using evolutionary model. GTO debris orbits are modeled as a reference of distribution of actual objects in GTO extracted from JAXA’s initial population file. Firstly, three cases of simulation with different perigee altitude were shown taking into accounts the distribution of GTO debris. It indicated that the debris with perigee altitude of over 400 km have long term effects while the debris with perigee altitude of 200 km decay shortly. The effect of continuously generation of GTO debris was secondly investigated. Since the GTO debris has long term orbital life, the number of its debris would keep increasing and accumulate in orbit. Lastly, the risk of GTO debris considering the actual number of debris and future works were discussed.

開催年月日： 2022年2月 - 2022年3月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Beppu-Oita   国名：日本国  

This study addresses and models the features of the global error accumulation generated though a numerical orbit prop- agation. To obtain fundamental findings and insights, the Cowell’s form, Runge-Kutta-Fehlberg (4, 5) method, and a variable step-size method are considered as the form of equation, numerical scheme, and stepping method, respectively. By measuring and observing the error generated, it is revealed that the error grows in proportion to the desired tolerance, squared calculation span, and squared mean motion. The influence of eccentricity is also investigated. The error accumulation model proposed here is valid for orbits whose eccentricity is less than 0.1 under the geopotential and third-body perturbations. Under the atmospheric drag and solar radiation pressure in association with the shadow of the Earth, the features of error accumulation cloud be more or less distorted. The findings and the model presented here enable evaluating the intrinsic error in the result from a numerical orbit propagation in a quantitative way.

開催年月日： 2022年2月 - 2022年3月

記述言語：英語  

開催地：Beppu-Oita   国名：日本国  

This study proposes a method of classification prior to identification of space debris fragmented in a low earth orbit, which are detected through a ground-based observation. The proposed method is incorporated by a concept of Admissible Region, which can give a reasonable region of unknown two-dimensional parameters such as time-derivative of declination and right ascension for an observational direction. As the two unknown parameters are necessary to estimate orbital elements from observation data obtained through a radar system or a telescope, a method to find their existence region leads to effectively classify the radar observation data based on their orbital elements. The classification method derived in this study is finally verified using results of a correlation analysis between cataloged fragmentation debris and observation data obtained in a campaign at EISCAT Svalbard Radar in 2020.

researchmap

開催年月日： 2022年2月 - 2022年3月

記述言語：英語  

開催地：Beppu-Oita   国名：日本国  

Because of the expansion of outer space activities, space debris is increasing considerably. To sustain the outer space activities, it is necessary to inhibit the generation and increase of space debris by active debris removal. By evaluating “timeliness”, this study determines the space debris to be removed which is a significant issue to improve the orbital environment efficiently. Then, the aims of this study are 1) proposing new evaluation indices considering dangerousness and timeliness and 2) discussing the effects of the indices on future environmental improvement. First, by focusing on the origins of space debris in the future orbital environment from the results of future projections, the necessary factors for the evaluation index are examined. Second, by applying the ridge regression model, the weighting of each factor is evaluated and then new evaluation indices are proposed. Finally, by discussing the future orbital environment following the removals of the objects selected by new evaluation indices, these indices have great effects for future environmental improvement.

researchmap

開催年月日： 2022年2月 - 2022年3月

記述言語：英語  

開催地：Beppu-Oita   国名：日本国  

The effects of GTO debris to LEO environment are revealed using evolutionary model. GTO debris orbits are modeled as a reference of distribution of actual objects in GTO extracted from JAXA’s initial population file. Firstly, three cases of simulation with different perigee altitude were shown taking into accounts the distribution of GTO debris. It indicated that the debris with perigee altitude of over 400 km have long term effects while the debris with perigee altitude of 200 km decay shortly. The effect of continuously generation of GTO debris was secondly investigated. Since the GTO debris has long term orbital life, the number of its debris would keep increasing and accumulate in orbit. Lastly, the risk of GTO debris considering the actual number of debris and future works were discussed.

researchmap

開催年月日： 2022年2月 - 2022年3月

記述言語：英語  

開催地：Beppu-Oita   国名：日本国  

This study addresses and models the features of the global error accumulation generated though a numerical orbit prop- agation. To obtain fundamental findings and insights, the Cowell’s form, Runge-Kutta-Fehlberg (4, 5) method, and a variable step-size method are considered as the form of equation, numerical scheme, and stepping method, respectively. By measuring and observing the error generated, it is revealed that the error grows in proportion to the desired tolerance, squared calculation span, and squared mean motion. The influence of eccentricity is also investigated. The error accumulation model proposed here is valid for orbits whose eccentricity is less than 0.1 under the geopotential and third-body perturbations. Under the atmospheric drag and solar radiation pressure in association with the shadow of the Earth, the features of error accumulation cloud be more or less distorted. The findings and the model presented here enable evaluating the intrinsic error in the result from a numerical orbit propagation in a quantitative way.

researchmap

開催年月日： 2021年12月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：横浜市港北区   国名：日本国  

This paper illustrates and explains the benefits of Laser-based Wireless Power Transmission system models, including functional principles and mathematical formulation. Wireless power transfer is a possible solution to deliver continuous, convenient, and unlimited energy supply to satellites. Satellite industries traditionally use photovoltaic cells and nuclear generators to satisfy the demand for electricity required by spacecraft. Current power generation and management systems occupy a considerable portion of up to 10-25% of the satellite's mass. The concept of laser-based wireless power transmission from Space Solar Power Satellite can solve significant problems. The current design of Space Solar Power Satellite primarily focuses on creating a massive satellite to generate and transmit gigawatts of energy to an Earth-based ground receiving antenna. This idea can be adopted for spacecraft by developing a constellation of small-scale Space Solar Power Satellites or Energy Orbit to supply sufficient power to spacecraft within range. The theoretical and simulation modeling allows the analysis of power conversion or transmission for each individual unit in terms of the impacts of laser, transmission efficiency, and photovoltaic-cell thermal property. Maximum power transmission efficiency is calculated based on a linear approximation of power conversation between electricity-to-laser and laser-to-electricity validated by numerical simulation. This efficiency variation depends on the selection of Laser, transmitter, transmission distance, and photovoltaic cells, precisely increasing the maximum transmission efficiency of information in a wireless communication network. Consequently, this paper gives insight into wireless power transmission in general and adequate guidelines of the satellite to satellite power transmission system design in practice.

開催年月日： 2021年11月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：online   国名：日本国  

This paper introduces a method of verifying the effect of a passive debris removal method focusing on the speed. While calculating the number of debris removed by the PDR satellite, the selected way is always ANCAS for its high precision. However, if the number of debris is vast, the time it takes will be too long. As a result, a solution to shortening the computation time is obtained efficiently using a series of prefilters that eliminate many cases from further consideration. This approach produces reliable results efficiently while dealing with the problem.

開催年月日： 2021年11月

記述言語：日本語  

開催地：山形県山形市（オンライン）   国名：日本国  

This paper describes results of an analysis for certain groups of fragmentation debris in low earth orbit, which were detected via EISCAT radar during a campaign in 2020. In order to separate known or so-called the cataloged objects from the actually observed ones, a correlation analysis is conducted. Whereas some objects, especially the targeted space debris in the observation campaign are relatively well sorted, many other ones are not, which seem to be caused from specific effects from a typical radar observation. This paper also discusses about observed objects which were not correlated with the cataloged objects.

開催年月日： 2021年11月

記述言語：日本語  

開催地：山形県山形市（オンライン）   国名：日本国  

This paper proposes an attitude stabilization method for a non-cooperative satellite using laser ablation. Due to the nature of laser ablation, the system has constraints in the direction of control torques. Such constraints disable generating desired　torques in three-dimensional directions, and generated torques partially yield disturbances for attitude stabilization. The proposed method in this paper minimizes the undesirable disturbance torques, where the irradiation spot of laser is theoretically clarified. Numerical simulations are conducted to verify and discuss the effectiveness of the proposed method.

開催年月日： 2021年11月

記述言語：日本語  

開催地：山形県山形市（オンライン）   国名：日本国  

With the expansion of the information infrastructure such as the launch of large constellation of satellites, the orbital environment is becoming more densely populated, and there is a need for the navigation focused on emergency from the viewpoint of Space Situational Awareness. This paper proposes a method for estimating the relative orbit of spacecraft with unknown thrust accelerations. In relative orbital motion, the target motion with unknown maneuver is estimated with optical observations (i.e., azimuth and elevation angles of non-resolved images). The proposed method estimates the thrust history　of the target satellite by expressing it with a Fourier series expansion formula.changes are evaluated.

開催年月日： 2021年11月

記述言語：日本語  

開催地：山形県山形市（オンライン）   国名：日本国  

This paper addresses the degree of an impact of the fidelity of Earth shadows modeled on orbit propagation accuracy for spacecrafts orbiting Earth. When reproducing Earth shadows, there are two essential parts: the geometry and the solar ephemeris. Lots of them are introduced and utilized now for the orbit propagations. With demonstrating the gap of propagation results occurred due to the condition difference, this paper offers a clue of how to consider the fidelities of　Earth shadow and solar radiation pressure properly so that propagation results satisfy desired accuracy.changes are evaluated.

開催年月日： 2021年11月

記述言語：日本語  

開催地：山形県山形市（オンライン）   国名：日本国  

This paper conducts an observability analysis for attitude estimation of space debris with light curves considering self- shadowing. Light curves, which are time-varying apparent brightness of objects, are obtained as photometric observations for attitude estimation of space debris. The difficulty of the attitude estimation with light curves stems from sparse and limited observations. To improve the estimation accuracy, self-shadowing is incorporated with the observability analysis. As a preliminary study, this paper investigates the self-shadowing effect in the light curve observations and its observability changes are evaluated.

開催年月日： 2021年11月

記述言語：日本語  

開催地：山形県山形市（オンライン）   国名：日本国  

While the scale of outer space activities is expanding, space debris is also increasing considerably. To sustain outer space activities, it is necessary to prevent the increase of space debris by Active Debris Removal (ADR). One of the problems in ADR is to determine targets to be removed from the orbital environment. Previous studies have proposed several indices to evaluate whether debris must be removed or not, but different indices yield different results for removal targets. Therefore, further discussion is needed to establish an effective and reliable index. This paper proposes a new index that focuses on　timeliness using space debris evolutionary model and regression models to obtain further improvement effects.over a long period of time because larger time steps can be employed to reduce the computational time.cataloged objects.

開催年月日： 2021年11月

記述言語：日本語  

開催地：山形県山形市（オンライン）   国名：日本国  

To counter the increasing threat of space debris in recent years, simulation tools for projecting the future population of space debris have been developed. It is indispensable for more accurate projection to improve the accuracy of orbit propagation. Therefore, this study compares methods (stepper) and step-size to solve a set of differential equations of motion to find out a better orbit propagation.

開催年月日： 2021年11月

記述言語：日本語  

開催地：山形県山形市（オンライン）   国名：日本国  

The number of objects in LEO region is increasing and the accurate tracking of all objects around the Earth is important. This paper studies the application of dual quaternions to attitude and orbit propagation. Dual quaternions are the extended concept of quaternions, which are widely used to describe attitude angles because of its singularity-free property. Since the set of dual quaternions forms a Lie group under the dual quaternion multiplication, Lie group geometric integration methods can be applied to integrate the state equation. This paper evaluates the accuracy of the calculation between a conventional Runge–Kutta method and the Crouch–Grossman (geometric integration) method. The results show that especially when larger time steps are considered, the Crouch–Grossman method outperforms the conventional Runge–Kutta method in terms of the structure preservation and the accuracy. This means that geometric integration schemes can be useful for propagation over a long period of time because larger time steps can be employed to reduce the computational time.cataloged objects.

開催年月日： 2021年10月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Dubai   国名：アラブ首長国連邦  

Remediation measures, such as Active Debris Removal (ADR) has been studied in order to preserve the space environment. Large derelict objects in crowded orbits because they are the source of numerous small debris in case of fragmentation. The target for removal must be chosen carefully because cost is the major issue in realizing ADR, and it is necessary to remediate the orbital environment as efficiently as possible. Last year, Dr. McKnight et al. presented the top 50 debris removal targets by combining each of the top 50 lists compiled by eleven international teams. This paper discusses the considerations involved in selecting debris removal targets. The study first considered the top 50 objects in each index to be removed then evaluated the consequences of the removal using Near-Earth Orbit Debris Environment Evolutionary Model (NEODEEM), a debris evolutionary model developed by Kyushu University and JAXA. Differences in debris removal targets were studied for long-term stability or short-term safety. The paper discusses why some indices are effective in the short or long term in terms of the orbital distribution of selected targets and the effects of removal in each altitude band. The paper also discusses the differences between removing 50 objects and removing one object each year, and the effects of removal timing and so on. The study found that integrating different indices is effective, and that the removal target must be determined according to the situation. It is more important to remove as much debris as possible as early as possible rather than focusing on an object’s ranking in a list.

開催年月日： 2021年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：St Petersburg   国名：ロシア連邦  

This paper illustrates and explains the benefits of Laser-based Wireless Power Transmission system models, including functional principles and mathematical formulation. Wireless power transfer is a possible solution to deliver continuous, convenient, and unlimited energy supply to satellites. Satellite industries traditionally use photovoltaic cells and nuclear generators to satisfy the demand for electricity required by spacecraft. Current power generation and management systems occupy a considerable portion of up to 10-25% of the satellite's mass. The concept of laser-based wireless power transmission from Space Solar Power Satellite can solve significant problems. The current design of Space Solar Power Satellite primarily focuses on creating a massive satellite to generate and transmit gigawatts of energy to an Earth-based ground receiving antenna. This idea can be adopted for spacecraft by developing a constellation of small-scale Space Solar Power Satellites or Energy Orbit to supply sufficient power to spacecraft within range. The theoretical and simulation modeling allows the analysis of power conversion or transmission for each individual unit in terms of the impacts of laser, transmission efficiency, and photovoltaic-cell thermal property. Maximum power transmission efficiency is calculated based on a linear approximation of power conversation between electricity-to-laser and laser-to-electricity validated by numerical simulation. This efficiency variation depends on the selection of Laser, transmitter, transmission distance, and photovoltaic cells, precisely increasing the maximum transmission efficiency of information in a wireless communication network. Consequently, this paper gives insight into wireless power transmission in general and adequate guidelines of the satellite to satellite power transmission system design in practice.

開催年月日： 2021年2月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

The building of space debris evolutionary models makes it possible to discuss how to reduce space debris and improve future orbital environment. In order to have a better discussion, it is essential to improve the accuracy of estimation in space debris evolutionary models. In collision breakup models implemented in current space debris evolutionary models, it is somewhat unrealistic that the distribution of fragments generated during a collision depends on the primary object. Therefore, this paper proposes a method to determine which object generated each fragment and form the distribution of fragments not only around the primary object but also around the secondary object. This paper also compares future orbital environment before and after the improvement of collision breakup models and describes differences of future orbital environment by improved collision breakup models.

開催年月日： 2021年2月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

Space debris is an emerging global environmental problem. PMD of 90% and ADR of 5 to 10 every year is required for maintaining the status of LEO. Fulfillment rate of PMD is, however, still in unsatisfied level and its associated cost of ADR is unclear. This provides the challenge from both of technology and economics. Previous studies on economics of space debris are mostly analogy from environmental problems on the earth. Environmental economics, holding two Nobel Prize winners, can potentially provide key tool to understand this problem. In this study, we provide how environmental economics merits on understanding and solving debris problem including cost of PMD and ADR. Finally, we discuss requirements for economic scheme which are acceptable in international space scene.

開催年月日： 2021年2月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

The orbital congestion is becoming an urgent issue with increasing space activities, such as satellite constellations for high-speed and large-capacity communications. Therefore, SKY Perfect JSAT Corporation has started out designing and developing an ADR satellite. The satellite applies laser ablation technologies so that it does not require any physical contact with a target object. ADR mission generally requires grasping the rotational motion of the target object in advance and reflecting it in its mission operations. The target object’s motion is usually complicated due to various disturbance torques acting on it. This presentation shows the short-term and long-term variation of attitude and angular velocities of the target object in Low Earth Orbit, considering the shift of the center of gravity.

開催年月日： 2021年2月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

A debris evolutionary model is indispensable for investigating effective debris mitigation measures and for developing international rules regarding space debris. JAXA has been evaluating the future space debris population using an evolutionary debris model named NEODEEM, developed in collaboration with Kyushu University. A baseline file is required for the debris Evolutionary model, which is the initial population data of the on-orbit environment, such as mass characteristics and orbits of all objects larger than 10 cm. JAXA has created its own baseline file by taking into account the area-mass-ratio evaluation from the TLE (Two Line Elements) history, literature review, and uncatalogued objects observed with the JAXA telescope, and so on. The baseline files provided by ESA at IADC have been used for research purposes only, but due to lack of information, for example, evaluation of specific debris removal targets was not possible. In this talk, the methods for developing the baseline file, the results of comparison with some debris models, and the results of debris evolutionary model predicted using the developed baseline files are reported. In particular, the evaluation of debris removal targets and the effectiveness of debris mitigation measures using the developed baseline files are introduced. In addition, the information that can be analyzed from the TLE history survey is introduced.

開催年月日： 2021年2月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都調布市   国名：日本国  

For the purpose of effective utilization of the orbital environment, the environmental capacity tolerance of insertions is studied using an orbital debris evolutionary model, developed in collaboration with Kyushu University. By inserting multiple spacecraft into a specific orbit regime and observing the impact on the orbital environment, the number of spacecraft that can be inserted into orbit (orbit insertion capacity tolerance) is evaluated. In this presentation, the results of studying the orbit insertion capacity tolerance due to differences in orbital regime, the number of inserted spacecraft, etc. Fig.1 demonstrates the difference in Effective Number of objects in LEO (Low Earth Orbit: altitude 200 to 2000 km) with and without 3000 spacecraft inserted into various orbital regimes. At altitudes below 800 km, natural decay due to the atmosphere may suppress the impact of insertions (and the generated debris). At altitudes between 800 and 1000 km, however, a remarkable increase in objects can be observed because of the many orbital residuals.

開催年月日： 2021年1月 - 2021年2月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Sydney   国名：オーストラリア連邦  

Dynamic states such as shape, attitude, and surface properties are essential information to carry out active debris removal (ADR) and/or to check up operational states of satellites. A cost-effective measure is to inversely estimate dynamic states using light curves, a time history of light intensity reflected in surfaces of orbital objects. One of the difficulties of light curve inversion is that estimation accuracy is dependent on initial attitude angles and initial angular velocities, which comes from less information obtained by the observer compared to plural parameters to be estimated. Previous studies have determined initial states by using the image obtained by radar or adaptive optics. The problem is that previous studies require additional expensive equipment and do not take full advantage of cost-effectiveness of light curve inversion. This paper proposes a state estimation technique that can be completed only with light curves without using high-cost extra instruments by focusing on the rapid change of light intensity, called glint. Although high observability in the vicinity of glint is shown in previous studies, it is difficult to use glint as measurement data and estimation accuracy rather drops immediately after glint because of its high frequency. The proposed method in this paper is based on geometric constraints among the Sun, the observer and surfaces of orbital objects in glint detection. This paper formulates constraint conditions of glint mechanism, and also evaluates the accuracy of state estimation method using glint. Physically meaningless values that did not satisfy the geometric constraints in glint detection are presumed to be excluded from the estimation. Thus, numerical simulations verify that the proposed method can estimate the attitude of a space object with higher accuracy than conventional methods shown in previous studies. It is concluded, therefore, that the attitude estimation method using glint can realize an inexpensive and highly accurate attitude estimation that can be completed only with light curves.

開催年月日： 2021年1月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Virtual Event   国名：その他  

Among various satellite actuators, magnetic torquers have been widely equipped for stabilization and attitude control of small satellites. Although magnetorquers are generally used with other actuators, such as momentum wheels, this paper explores a control method where only a magnetic actuation is available. We applied a nonlinear optimal control method, Nonlinear Model Predictive Control (NMPC), to small satellites, employing the generalized minimal residual (GMRES) method, which generates continuous control inputs. Onboard magnetic actuation systems often find it challenging to produce smooth magnetic moments as a control input; hence, we employ Pulse Width Modulation (PWM) method, which discretizes a control input and reduces the burden on actuators. In our case, the PWM approach discretizes control torques generated by the NMPC scheme. This study's main contributions are investigating the NMPC and the GMRES method applied to small spacecraft and presenting the PWM control system’s feasibility.

その他リンク： https://doi.org/10.2514/6.2021-0559

開催年月日： 2020年12月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2020年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：熊本市   国名：日本国  

This study aims to design realistic multi-rendezvous trajectories for multiple removal spacecraft in low earth orbit.　　Genetic Algorithms is adopted to optimize the order of multi-rendezvous and the orbital parameters of the parking orbits,　which minimize the velocity increment necessary for changing orbital planes between removal targets. 　Although single　spacecraft may successfully rendezvous with selected targets within reasonable amounts of velocity increment and time,　subsequent spacecraft need large velocity increment and time to complete the multi-rendezvous.　　Rendezvous trajectory　design by utilizing not only incremental velocity but also nodal regression due to J2 perturbation in LEO obtains the reasonable solutions, however, it is necessary to optimize the whole, not partially to sustain the outer space activities.

開催年月日： 2020年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：zoom.us   国名：日本国  

Space Elevator is a space transportation system for carrying payloads to outer space through tethers that connect between ground and outer space stations. Assumed that the construction cost of a space elevator can be recovered in 10 years, this paper evaluates the survivability of the space elevator after 10 years against space debris impacts. As a result, it is difficult to realize the space elevator without environmental remediation down to less than 10% of the present space debris population.

開催年月日： 2020年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：zoom.us   国名：日本国  

開催年月日： 2020年10月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：The CyberSpace Edition   国名：その他  

Ever since humans have landed on the moon, many space agencies have investigated the Moon, Mars, and asteroids, driven by the quest for knowledge and future space missions. For the interplanetary mission, space engineers are working on the satellite, conceptual design of space habitat, and exploration system. The state of the art in those missions relies on the radioisotope thermoelectric generator or solar panel attached with batteries to store power, which is plagued by certain limitations. For instance, the collection of solar energy is inversely proportional to the distance from the Sun. Moreover, to run the central processing unit, avionics and payload inside the spacecraft requires constant monitors of temperature. In addition, this power generation unit of satellites carries a pack of batteries to store energy, which makes more than 10 - 25 % of the weight of the satellites. In hindsight, space solar power satellite serves a potential for a more reliable source of energy transmission as compared to the traditional method. Space agencies have already studied space solar power station designing concepts for gigawatts wireless power transmission systems from space to Earth to fulfil global electricity demand. Yet another avenue where space solar power satellites support an application is its utility towards rovers and habitat. For instance, the rovers on the Moon and Mars moves very slow to maintain performance for a lifetime. On Mars, sandstorms affect the collection of energy at the attached solar panel to the rover. Furthermore, a difficult to investigate in the far side, crater, and polar region of the Moon, where sunlight is unavailable for a few days. This challenge can be suitably overcome by employing a space solar power satellite, which can be used for wireless power transmission, independent of its location. Such techniques demonstrate possible applications towards power transmission for unmanned aerial vehicles for faster mapping purposes. As such, the dependence of those aerial vehicles towards fixed energy storage becomes alleviated. In this paper, we are comparing power generation by traditional method vs space solar power satellite. Simultaneously the future habitat on Mars and the Moon will receive continuous power by developing a perfect small space solar power satellite system for interplanetary and solar-system investigation mission satellites to achieve continuous power.

開催年月日： 2020年4月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：online   国名：日本国  

SKY Perfect JSAT Co. has launched a new mission, which removes non-functional spacecraft by laser ablation from a satellite-mounted laser with keeping a safe distance, in order to achieve space sustainability in collaboration with RIKEN, JAXA, Nagoya Univ., and Kyushu Univ. Laser ablation takes advantage in control the attitude of tumbling objects. And recent progress of laser technology has increased the feasibility to mount such lasers on small satellite.

開催年月日： 2020年1月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Orlando, FL   国名：アメリカ合衆国  

This research proposes an innovative approach to detumble satellites’ triple-axis angular velocities with only one single-axis magnetic torquer. Since magnetic torque is generated perpendicularly to magnetorquers, no intended control torque along the magnetorquer can be produced, which makes systems underactuated. Our paper introduces a control method using Model Predictive Control (MPC) and compares it with B-dot control algorithm. By applying these control laws to Kyushu University Light Curve Inversion (Q-Li) Demonstration Satellite in numerical simulations, we describe the applicability of these control laws to underactuated systems.

その他リンク： https://doi.org/10.2514/6.2020-1433

開催年月日： 2019年12月

記述言語：英語  

開催地：Sugarland, TX   国名：アメリカ合衆国  

Grasping of dynamic states of space objects such as shape, attitude, and surface properties plays a significant role in removing orbital debris and in monitoring the health of operational satellites. Light Curve Inversion is a cost- effective state estimation technique using light curves, a time history of magnitude obtained by ground-based observations. The problem of this method is, however, that the observer measure only scalar data regardless of plural parameters to be estimated so that estimation accuracy is dependent of the initial values of estimation procedure. This study proposes a high-accurate estimation method using only light curves focusing on their characteristic, especially the sudden change of magnitude, called “glint”. Constrained conditions governing glint detection are shown in this paper. They are essential to exclude meaningless values from initial value candidates by setting attitudes in glint detection as the initial state values. Moreover, they realize a high-accurate estimation regardless of the initial values by efficient update of states and covariance matrix with constrains in the estimation filter.

開催年月日： 2019年12月

記述言語：英語  

開催地：Sugarland, TX   国名：アメリカ合衆国  

The collision probabilities of debris objects with and without Post Mission Disposal (PMD) and Active Debris Removal (ADR) are evaluated and discussed. A debris evolutionary model named NEODEEM was jointly developed by Kyushu University and JAXA for use in predicting future debris populations and calculating collision probabilities. The collision probability in each altitude bin is initially compared with and without PMD or ADR. Then a case involving a large satellite constellation is also discussed. The effective number of debris objects at each altitude for the PMD success rates of the large constellation and the collision probability at each altitude are calculated. The collision probability per unit time will increase when a small satellite utilizes a drag augmentation sail or a tether as a PMD device, but the dwell time will be greatly reduced. A collision with a sail or tether will be non-catastrophic collision. Therefore, the use of such devices will reduce the cumulative collision probability and expected number of debris fragments.

開催年月日： 2019年12月

記述言語：英語  

開催地：Sugarland, TX   国名：アメリカ合衆国  

Debris with size less than 2 mm is called sub-millimeter debris. They have enough energy to cause fatal damage on a spacecraft, but cannot be tracked from the ground. Kyushu University has initiated the development of the in-situ measurement satellite to have a better understanding of the sub-millimeter-size debris environment. In order to investigate the natures of orbital planes on which debris may impact with the measurement satellite, the previous study has developed a collision flux model, to estimate the collision flux of debris into the measurement satellites, assuming both debris and measurement satellites are on circular orbits. This paper generalizes the previous assumption to be applicable to elliptical orbits. This paper proposes an environmental estimation model that estimates the distribution of sub-millimeter-size debris by using in-situ measurements by applying the nature to the algorithm of the particle filter. Finally, the proposed model using the particle filter is verified by numerical simulation using MASTER-2009.

開催年月日： 2019年12月

記述言語：英語  

開催地：Sugarland, TX   国名：アメリカ合衆国  

Photometric data obtained by ground-based observation provide much information of space objects such as their orbit, attitude, shape, and surface properties, which are useful sources for Space Situational Awareness (SSA). Such complicated and coupled information, however, makes state estimation with photometric data difficult, because expressing an object shape and its surface properties requires many parameters for each component. To tackle this problem, this paper formulates the object shape and its surface properties with a fewer number of parameters using spin averaging. Furthermore, they are explicitly related to the dynamics of the rotational motion considering solar radiation pressure. The proposed formulation can approximate light curves to be obtained, reducing the number of parameters for estimation. Numerical examples using the proposed approximation are provided to demonstrate the effectiveness of the proposed formulation.

開催年月日： 2019年12月

記述言語：英語  

開催地：Sugarland, TX   国名：アメリカ合衆国  

Space business in recent years has reached a major turning point. One of the factors is that technological innovation has led to cost reduction and miniaturization of rockets and satellites, and the barrier to enter into space industry has been lowered. Constellation systems are attracting attention in recent years as new technologies. A constellation system is the system that achieves one mission using multiple satellites. Conventional satellite constellations have been used to deploy dozens of large satellites like GPS and Iridium, whereas recent satellite constellations for space broadband systems plan to launch 1000 or more small satellites at an altitude of 1000 km. Such a large-scale system is called a large constellation. There is a possibility that such a small satellite constellation will drastically change the way of space utilization. When a satellite breaks up, hundreds of thousands of space debris are generated (Fig.1). They continue to drift in space because there is not much natural purification effect around 1000 km altitude, and thus debris removal for the large constellation is necessary. Removal methods are categorized into two approaches; active debris removal and passive debris removal (PDR). Active debris removal is typically used for large debris, while passive debris removal is used for small debris (Fig.2). Even small debris need to be removed because they have enough energy to destroy satellites in operation. PDR satellites reduce kinetic energy by letting them penetrate debris and remove them by forcing them into the atmosphere by reducing the orbital radius of the debris. This study investigates the effectiveness of velocity decay of debris using PDR.

開催年月日： 2019年12月

記述言語：英語  

開催地：Fukuoka-shi   国名：日本国  

開催年月日： 2019年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：熊本市   国名：日本国  

The space elevator is a space transportation system to carry payload to outer space through a tether connecting between stations on the ground and in outer space. Its transportation cost is approximately one-tenth of the present transportation cost, so that it is possible to expect a substantial cost reduction. However, considering the collision of the space elevator with space debris, the survival probability of the space elevator after 10 years is nearly 0%. Therefore, this paper proposes a highly redundant system against space debris and an effective environmental remediation.

開催年月日： 2019年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：熊本市   国名：日本国  

Space debris has become a huge problem for outer space activity in the space. Observations are conducted around the world to detect and track space debris. One of the important problems in optical observation is how to get useful information from large amounts of image data to determine the orbit of space debris. In order to determine the orbit of space debris in the geostationary region, this paper proposes a new method to detect space debris and its trajectories from a series of images. Then, a Particle filter is applied to determine the orbit of space debris. This paper also verifies that the proposed method can successful determine the orbit of space debris.

開催年月日： 2019年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：熊本市   国名：日本国  

In order to detect and identify fragmentation space debris in low-earth orbit (LEO), observation experiments using EISCAT radar in the Scandinavian Peninsula have been conducted. This study aims to derive an efficient method for observation of unknown and known space debris originated from break-up events occurred to artificial satellites or spacecraft in LEO. Whereas the past study applied a stepwise method combining predicted orbital position distributions of cataloged space debris and a predictive observation simulation for them based on their Two-Line-Element (TLE) data and orbit propagation algorithms, this study takes an analytical approach using 2-dimensional histogram to the above predicted orbital position distributions considering their time change. The effectiveness of the derived method is also shown through comparing with results of a past observation campaign.

開催年月日： 2019年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：熊本市   国名：日本国  

Outer space activities are currently developing. At the same time, space debris are increasing considerably, so that Active Debris Removal (ADR) is necessary to prevent an increase in space debris that affect outer space activities. One of the problems in ADR is to determine targets to be removed from the environment. Priority Lists depending on various indexes have been proposed, but are too different to trust. This paper compares the resulting space environment based on various Priority List proposed herein to find out the right space debris index that can make the space environment better.

開催年月日： 2019年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：熊本市   国名：日本国  

Cleaning up space debris out there is recently needed for environmental remediation. Tether satellite system is one of those candidates. That satellite system is known that it has many prospects to achieve such missions. However, there are difficulties on analysis of the behavior of those tether satellite systems due to elastic behavior of tether. Because of that, the step-size when integrating the equations of motion is empirically set to a small constant value to stabilize the behavior. In that context, this research proposes a new analysis method which can set the step-size adaptively. In particular, we apply distance function to settle the problem.

開催年月日： 2019年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：徳島県徳島市   国名：日本国  

An impact of space debris smaller than 2 mm, which cannot be detected by ground-based observations can cause a fatal damage on a spacecraft. Therefore, in-situ measurements that detect small debris utilizing on-orbit impact sensors are promoted to monitor the environment of small debris. This paper proposes two statistical methods that detect environmental changes utilizing time-series impact data obtained by in-situ measurements. The first and the second methods focus on drastic and continuous changes of environment, respectively. This paper also demonstrates the statistical detection of environmental changes with numerical simulations. The simulations and discussions in this paper clarifiy correlations between area of impact sensor, mission duration and detectable scale of environmental changes. Outcomes of this paper can contribute to design in-situ measurement missions.

開催年月日： 2019年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：徳島県徳島市   国名：日本国  

開催年月日： 2019年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：徳島県徳島市   国名：日本国  

An impact of space debris smaller than 2 mm, which cannot be detected by ground-based observations can cause a fatal damage on a spacecraft. Therefore, in-situ measurements that detect small debris utilizing on-orbit impact sensors are promoted to monitor the environment of small debris. This paper proposes two statistical methods that detect environmental changes utilizing time-series impact data obtained by in-situ measurements. The first and the second methods focus on drastic and continuous changes of environment, respectively. This paper also demonstrates the statistical detection of environmental changes with numerical simulations. The simulations and discussions in this paper clarifiy correlations between area of impact sensor, mission duration and detectable scale of environmental changes. Outcomes of this paper can contribute to design in-situ measurement missions.

開催年月日： 2019年10月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Washington D.C.   国名：アメリカ合衆国  

Active Debris Removal (ADR) has been studied in order to preserve the space environment. Large debris objects such as defunct rocket upper stages and satellites in crowded regions are considered ADR targets, but it is important to identify which debris objects and how many debris objects should be removed. Future environmental changes have been evaluated by using a space debris evolutionary model that considers future launch traffic, explosions, collisions, and other factors. This study evaluates the effectiveness of ADR strategy by using the Near-Earth Orbital Debris Environment Evolutionary Model (NEODEEM) that was jointly developed by Kyushu University and JAXA. The effectiveness of ADR is evaluated by comparing such different ADR indexes as collision probability multiplied by mass, the expected number of fragments generated, and other indexes. Each index is shown to be effective for suppressing the increase of space debris, even though ranking orders differ for each index. The effects of limiting targets are also discussed, such as debris type (e.g., only rocket upper stages), mass, and orbit range, by showing the relations between limiting ADR targets and the required number of ADR objects to suppress the increase of space debris. For example, limiting ADR targets to rocket upper stages with mass of less than 4 tons is shown to increase the number of debris objects to be removed each year. Moreover, the removal of debris objects at lower altitudes is shown not to be effective, even though such objects have higher collision probabilities. The effect of disposal orbits where debris objects are to be moved is compared by changing the altitude of disposal orbits. The effectiveness of ADR for a large satellite constellation is also discussed.

開催年月日： 2019年10月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Washington D.C.   国名：アメリカ合衆国  

This study aims to develop a new collision avoidance strategy for geostationary spacecraft. Recently, the continuous growth of space objects is increasing the collision risk among them. In the future, it will be necessary to operate the spacecraft while avoiding much space objects. However, there is a limit of fuel loading in a spacecraft, so it will be important to save fuel consuming each collision avoidance maneuvers not to shorten spacecraft lifetime rapidly. The proposed strategy considers the following points to save fuel and extend a spacecraft lifetime as much as possible. The first point is to avoid as many objects as possible at once maneuver so that the maximum collision probability is less than 1.0 × 10%&. The second point is to minimize fuel consumed by collision avoidance maneuvers and the next orbit maintenance maneuver. The last point is to maximize the period to keep a spacecraft in the station-keeping slot. To realize this strategy, multi-objective genetic algorithm optimizes maneuver time and maneuver vector. In the simulation, to simplify, a spacecraft avoids two approaching objects. The Spacecraft conducts collision avoidance maneuver as the East-West control maneuver and the North-South control maneuver, separately. As a result, in the case of once maneuver, collision avoidance is succeeded but the station-keeping period was too short, especially in the case of an East-West control maneuver. Therefore, it needs to conduct many maneuvers before the closest approach.

開催年月日： 2019年9月

記述言語：英語  

開催地：Maui, HI   国名：アメリカ合衆国  

Optical measurements such as photometric observations and imaging observations have been widely applied for the estimation of the shape, surface properties, and attitude motion of space objects. Those informations enable us to improve the efficiency of active debris removal (ADR) and to investigate the health of the satellites. Although photometric observation is low-cost, previous study pointed out that initial values of attitude are necessary for high-precision estimation. Imaging observation by image matching method was examined to estimate those initial values in the previous study, considering that imaging observation is effective, especially for GEO objects. The purpose of this paper is to improve accuracy, robustness, and calculation cost of imaging observation applying machine learning, and to reveal the system requirement of imaging observation of GEO objects. The feasibility of imaging observation with existing optical system was verified, and by imaging simulation with different resolutions. Also comparing Convlutional Neural Network (CNNs) with estimation based on conventional image matching, it was clarified that the problems in the previous research were overcome.

開催年月日： 2019年7月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都文京区   国名：日本国  

開催年月日： 2019年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Matsuyama-Ehime   国名：日本国  

Space debris smaller than 2 mm that cannot be detected by ground-based observations may lead to a spacecraft's missions end. Therefore, multiple institutes and organizations have conducted in-situ measurement projects including the IDEA (In-situ Debris Environmental Awareness) project, which has been initiated at Kyushu University. The previous research has proposed a statistical method that estimates the environment of sub-millimeter-size debris sequentially utilizing in-situ measurements. This paper aims to improve accuracy of the estimation result by a “feedback estimation” method that utilizes the measurement data multiple times. Furthermore, this paper also calculates “total likelihood” to evaluate the accuracy of estimation results quantitatively so that effectiveness of the feedback estimation can be discussed. The evaluation with the total likelihoods suggests that the feedback estimation method can increase the accuracy of the environmental estimation. In conclusion, this paper contributes the improvement in the environmental estimation on sub-millimeter-size debris utilizing in-situ measurement.

開催年月日： 2018年12月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：宇宙航空研究開発機構 調布航空宇宙センター   国名：日本国  

We propose that the cost of ADR (Active Debris Removal) can be paid by circulating digital currency tokens whose values decrease over time. Such tokens are issued by global cooperation (a consortium) of parties interested in space development to parties who actually performed ADR, in exchange with proofs of removals. The tokens represent debts of the consortium, which is repaid through contributions by the token holders (as values of tokens decrease while holding them), who are likely to be benefited by removal of debris. This scheme imposes virtually no cost to the consortium. We have generalized this concept as PoD (Proof of Disposal), which, we believe, provides a more accountable foundation for solving social problems with digital currency than many ICO (Initial Coin Offering) in practice today.

開催年月日： 2018年12月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：宇宙航空研究開発機構 調布航空宇宙センター   国名：日本国  

Kyushu University aims to establish a state estimation technique, called light curve inversion, which extracts dynamic states such as attitude motion and configuration from light curves. Light curves are brightness of space objects as a function of time and are obtained by ground-based observations. In order to demonstrate this technique, “Q-Li” the 3U Cubesat for Light Curve Inversion is being developed in Kyushu University. The primary mission of Q-Li is the on-orbit verification of the light curve inversion by comparing actual state and estimated one by light curve measurements. To this end, Q-Li deploys a membrane to reflect sunlight so that one can be observed from the ground. Q-Li measures her own attitude angles and angular rates in orbit and transmits them to the ground. As the secondary mission, Q-Li detects tiny debris collisions with the membrane by sensors located on its surface. In this workshop, not only the whole systems of Q-Li but also the deployment mechanism of the membrane and light curve inversion technique are presented.

開催年月日： 2018年12月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：宇宙航空研究開発機構 調布航空宇宙センター   国名：日本国  

Optical measurements such as photometric observations and imaging observations have been widely applied for estimating the shape, surface characteristics, and attitude motion of space objects. Photometric observation-based methods use light curves, the time history of the brightness of a space object, whereas imaging observation-based methods use images captured by the optical telescope and processed with adaptive optics. In Kyushu University, studies on the state estimation of space object with photometric observations have been conducted. In addition, an imaging observation-based method to determine an initial value for photometric observations and its feasibility have been studied. The current study describes a photometric observation-based method and verifies its accuracy by numerical simulations. Furthermore, a state estimation method that exploits both photometric observations and imaging observations is presented. The proposed method also shows the efficiency to apply image identification by convolutional neural network, a kind of machine learning, in imaging observations.

開催年月日： 2018年12月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：宇宙航空研究開発機構 調布航空宇宙センター   国名：日本国  

The orbital debris modeling can build evolutionary models as essential tools to predict the current or future orbital debris populations, and also to discuss what and how to do for orbital debris mitigation and environmental remediation. The orbital debris modeling can also devise an effective search strategy applicable for breakup fragments in the geostationary region using ground-based optical sensors, and to evaluate the effectiveness of space-based measurements of objects not tracked from the ground, both to contribute to space situational awareness. Another application of the orbital debris modeling is to estimate attitude motion of space objects to be removed for environmental remediation. This paper briefly introduces efforts into orbital debris modeling and applications.

開催年月日： 2018年12月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：宇宙航空研究開発機構 調布航空宇宙センター   国名：日本国  

Space debris smaller than 2 mm cannot be tracked or detected by ground-based observations even though an impact of such small debris can cause a fatal damage on a spacecraft. Therefore, the environment of sub-millimeter-size debris must be monitored utilizing in-situ measurements. This paper proposes a statistical method to estimate the environment of sub-millimeter-size debris utilizing in-situ measurements. The proposed method consists of a sequential Monte Carlo filter and natures of orbits on which debris may be detected by the satellite. This paper also evaluates that the proposed method can sufficiently estimate the environment utilizing simulated impacts onto the satellite. Furthermore, this paper describes modifications to apply the proposed method to measurement data obtained by a satellite in an elliptic orbit.

開催年月日： 2018年12月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：宇宙航空研究開発機構 調布航空宇宙センター   国名：日本国  

After the long space activities, large numbers of fragments generated by explosions and collisions of space objects are gradually increasing. In recent, many research organizations have reported that as a result of self-proliferation of these space debris without some mitigation process, future space activities will be affected. Also, in the private sector, mega constellation with thousands of satellites are also planned as a continuous communication infrastructure, and it should be necessary to consider the influence on the space environments. In this report, one guideline for improvement of future orbital environment after the result of space debris mitigation effect by some removal indexes for orbital objects with the propagation model of space debris created to predict the future debris distribution.

開催年月日： 2018年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：熊本市   国名：日本国  

Space debris has been jeopardizing the lives of many spacecraft around the Earth since the beginning of the space age. Debris with a size less than 2 mm are called sub-millimeter-size debris.They have enough energy to cause a fatal damage on a spacecraft , but cannot be tracked from the ground.For that reason，Kyushu University has initiated IDEA the project for In-situ Debris Environmental Awareness to have a better understanding of this yet unfamiliar sub-millimeter-size debris environment.In order to investigate the relationship between debris and measurement satellites，the previous study has developed a practical approximation method to calculate the collision flux of debris into measurement satellites，assuming that measurement satellites are on circular orbits.This paper proposes a new approximation method which can be applied to measurement satellites in elliptical orbits.

開催年月日： 2018年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：熊本市   国名：日本国  

This study aims to design realistic multiple space debris removal mission for long-term environmental remediation. In the previous study, as mission criteria, velocity increment for successive orbit transfers and mission duration are optimized. This study examines the case of active debris removal with multiple satellites. Therefore, the multi-objective genetic algorithm with quasi-optimum solutions is adopted to derive optimal solutions.

開催年月日： 2018年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：熊本市   国名：日本国  

Space-based optical observation for space debris has excellent advantages compared to ground-based observation. This paper proposes a new concept to evaluate the coverage performance by a constellation of satellites in Sun-synchronous orbit in terms of the number of orbital planes based on several geometrical models and reasonable assumptions. According to the initial assumptions of the research, when the number of orbital planes is 6 or 7, we find that the constellation will lose the observable coverage of one satellite which circling one circle around the earth.

開催年月日： 2018年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡県久留米市   国名：日本国  

This paper discusses a method to classify and estimate a distribution of the orbital elements for a cloud of debris fragments originated from a specific breakup event by utilizing data obtained from EISCAT radar observation. In the proposed method, by constraining admissible region of unobserved data set which are theoretically necessary to determine their orbits, the candidate objects as well as statistical distributions of their orbital elements are estimated from the original radar observation data. Finally, this study shows an effectiveness of the proposed method based on a real observation data.

開催年月日： 2018年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡県久留米市   国名：日本国  

This paper proposes a method to reevaluate closest approach between space objects. The purpose of this study is to confirm the effectiveness of the proposed method and determine the observation requirements. This study allows operators who own spacecraft to reevaluate closest approach by a telescope. The reevaluation method consists of optical observation, orbit determination, and conjunction assessment. Numerical simulations are conducted under the assumption that a collision occur in a geostationary orbit. The result shows that it is necessary to observe for two nights for orbit determination and three nights for conjunction assessment.

開催年月日： 2018年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡県久留米市   国名：日本国  

開催年月日： 2018年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡県久留米市   国名：日本国  

Relative attitude and inertial property estimation is an important phase in on-orbit servicing missions to provide information necessary for safe approach to a target object. Although the estimation usually uses optical devices, such observations may suffer from sudden change of the optical environment and intensive computational burden. To tackle these problems, this study shows an attitude and inertial property estimation method for an asymmetric target with low-rate observations. Using attitude angles periodically observed, the proposed method enables defining target states with constant parameters, which causes no error in state predictions of Kalman filter scheme even if the observation rate is low. Thus, the proposed estimation method is robust against the data deficiency and applicable with low-cost processors. Furthermore, the low-rate observations make the filtering easy to implement Iterated Extended Kalman Filter. Numerical examples verify the effectiveness of the proposed method and compare the results between Extended Kalman Filter and Iterated Extended Kalman Filter.

開催年月日： 2018年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡県久留米市   国名：日本国  

This paper describes a CubeSat named “Q-Li”, being developed at Kyushu University. The Q-Li intends to verify a light- curve inversion developed at Kyushu University for estimating the attitude motion of a spacecraft. The Q-Li deploys a sail with a high reflectance surface to make it easy to be observed from the ground, and records data of attitude motion using sensors to verify the light curve inversion. The verification can be conducted by comparing attitude motion between the light-curve inversion and the on-orbit measurement. This paper analyzes the mission of the Q-Li by simulating attitude motion and observed light curve. This paper also describes the design of the deployment sail. The design of the sail considers the reliability of deployment and the survivability against debris impacts.

開催年月日： 2018年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡県久留米市   国名：日本国  

This paper proposes and evaluates a method that estimates the environment of sub-millimeter-size debris utilizing in-situ measurements. Space debris smaller than 2 mm are too small to be detected by ground-based observations, in spite of the dangerousness of sub-millimeter-size debris. Therefore, the environment of sub-millimeter-size debris should be estimated on the basis of the in-situ measurement data. This paper establishes an estimation method with a sequential Monte Carlo filter, which befits non-linear estimation problems. The estimation method consists of the natures of the orbits on which debris may be measured in-situ. This paper also evaluates the proposed method by simulations with an existing environmental model. The simulations demonstrate that the proposed method can sufficiently estimate the sub-millimeter-size debris utilizing the in-situ measurement data.

開催年月日： 2018年10月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Bremen   国名：ドイツ連邦共和国  

Even sub-millimeter-size debris could cause a fatal damage on a spacecraft. However, such tiny debris cannot be followed up or tracked from the ground. Therefore, Kyushu University has initiated IDEA the project for In-situ Debris Environmental Awareness, which conducts in-situ measurement of sub-millimeter-size debris. One of the project’s objectives is to estimate the location of on-orbit satellite fragmentations from measurements. The previous study derived a constraint equation that applies for the orbital parameters of a broken-up object. The previous study also concluded that two or more measurement satellites are necessary to properly estimate a couple of orbital parameters of the broken-up object in certain special case. This study finds out that even a single measurement satellite can estimate the orbital parameters of the broken-up object. Furthermore, this study derives a new constraint equation that applies for the nodal regression rate of the broken-up object. Finally, this paper demonstrates an effective procedure for a single measurement satellite to estimate the location of on-orbit satellite fragmentations.

開催年月日： 2018年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Pasadena, CA   国名：アメリカ合衆国  

Space debris smaller than 2 mm, which cannot be tracked nor detected by ground-based observations, may cause a fatal damage on a spacecraft. To understand the environment of such sub-millimeter-size debris sufficiently, in-situ measurements and modeling should be conducted. Therefore, IDEA the project for In- situ Debris Environmental Awareness, which aims to detect sub- millimeter-size debris using a group of micro satellites, has been initiated at Kyushu University. To estimate the debris environment based on in-situ measurements from the project, this paper proposes an environmental model that estimates the population of sub-millimetersize debris utilizing the date, time and location at impact on a measurement satellite. The proposed environmental estimation is based on an algorithm of a particle filter, considering the natures of orbits on which debris can be detected by the in-situ measurement satellite. This paper also evaluates the proposed model with a simulation using MASTER-2009, which is the environmental model developed at European Space Agency. Comparison between the debris population predicted by MASTER-2009 and the simulated estimation verifies that the proposed model can estimate the debris environment. Collision flux estimated by the proposed model is also evaluated to predict the impact rate into the measurement satellite. It is concluded, therefore, that the estimation model proposed and evaluated in this paper can provide a better definition of sub-millimeter-size debris environment with in-situ measurements.

開催年月日： 2018年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Pasadena, CA   国名：アメリカ合衆国  

This paper investigates which debris are highly dangerous to exacerbate the future orbital environment based on the outcomes of an orbital debris evolutionary model with two different algorithms of collision risk assessment. One is “Two- Sphere Overwrap” collision risk assessment, which focuses on the geometrical relation between the orbits of the two colliding objects, calculates the collision risk on the assumption that the objects are closest to each other at the intersections of the orbital planes at an interval of one year. The other is “Cube” collision risk assessment, which focuses on the relative positions of the two colliding objects, calculates the collision risk when both objects are inside a cube with a side of 10 km at an interval of 5 days. The previous study by the second author (Dr. Zemoura) identified harmful debris to be removed based on the outcome of an orbital debris evolutionary model with the “Two-Sphere Overwrap” collision risk assessment. As a result, it was found that there are removal debris with short-term environmental improvement effect and removal debris with long-term environmental improvement effect. This paper identifies harmful debris to be removed based on the outcome of the same orbital debris evolutionary model but with the “Cube” collision risk assessment. Finally, this paper compares harmful debris to be removed between the previous and present outcomes and investigate how the harmful debris to be removed change as the collision risk assessment changes.

開催年月日： 2017年12月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Fukuoka-shi   国名：日本国  

開催年月日： 2017年12月

記述言語：英語  

開催地：Fukuoka-shi   国名：日本国  

開催年月日： 2017年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：熊本市   国名：日本国  

Defining a state of space objects by optical observation is major theme for many researchers. optical measurements of cosmic object enables us to obtain the information of attitude motion, surface characteristics and shape of the object which cannot be got by telemetry data. Using these information, we can contribute to grasp the health. Various methods exist for optical observation, but photometric observation and imaging observation are considered in this research. In this paper, we discuss the estimation of the attitude motion of a space object in the Geostationary region(GEO) using imaging observation. This analysis is based on simulations considering the performance of the AO system and the telescope and atmospheric fluctuation, and proposes the attitude determination method applying the method using computer vision. In the future, we aim at improving the accuracy of dynamic estimation by combining this method with photometric observation and clarifying the system requirements for actual observation.

開催年月日： 2017年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：新潟県新潟市   国名：日本国  

欧州非干渉散乱(EISCAT)レーダーを用いたスペースデブリ観測の研究概要および2016年度に行われた予備実験で得られた観測データ解析の結果について述べる．本研究では，本来地球の超高層大気の組成・動態解析を目的としたEISCATレーダーを地球周回低軌道上におけるスペースデブリ観測に適用することを目的としている．ここでは，３年間の研究計画中，初年度に行われた低軌道上の人工物体検出および同定を目的とした予備実験の概要，観測結果，および観測データから検出された人工物体の解析結果について説明を行う．

開催年月日： 2017年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Adelaide   国名：オーストラリア連邦  

Even sub-millimeter-size debris could cause a fatal damage on a spacecraft. However, such tiny debris cannot be followed up or tracked from the ground. Therefore, Kyushu University has initiated IDEA the project for In-situ Debris Environmental Awareness, which conducts in-situ measurement of sub-millimeter-size debris. One of the project’s objectives is to estimate the location of on-orbit satellite fragmentations from measurements. The previous study derived a constraint equation that applies for the orbital parameters of a broken-up object. The previous study also concluded that two or more measurement satellites are necessary to properly estimate a couple of orbital parameters of the broken-up object in certain special case. This study finds out that even a single measurement satellite can estimate the orbital parameters of the broken-up object. Furthermore, this study derives a new constraint equation that applies for the nodal regression rate of the broken-up object. Finally, this paper demonstrates an effective procedure for a single measurement satellite to estimate the location of on-orbit satellite fragmentations.

開催年月日： 2017年9月

記述言語：英語  

開催地：Adelaide   国名：オーストラリア連邦  

This study aims to devise an effective search strategy for fragments in Highly Elliptical Orbit by developing a precise estimation scheme for the initial breakup states and by updating a population evaluating scheme of the previous studies. As for the estimation of the initial breakup state, a newly developed equation was introduced. This equation restricts initial distribution of orbital planes of fragments by using the parental object’s right ascension, inclination, right ascension of ascending node, and argument of perigee. The advantage of this constraint is that the fragments can be evaluated by using only two orbital elements which can guarantee relatively high propagation accuracy. A hybrid scheme combined with close approach analysis was proposed to estimate the initial breakup state including the breakup date and time. In the observation planning, this study utilized previous strategy aimed for breakups in Geostationary Orbit. This study upgraded the previous strategy by introducing separation angle between observation direction and direction of a fragment, so that high latitude areas are also evaluated properly. As a result, by using officially reported data, it was confirmed that the initial state estimation scheme for breakup can estimate the initial state precisely, and updated method can evaluate the population of fragments having high inclination.

開催年月日： 2017年9月

記述言語：英語  

開催地：Maui, HI   国名：アメリカ合衆国  

Defining a state of space objects by optical observation is major theme for many researchers. optical measurements of cosmic object enables us to obtain the information of attitude motion, surface characteristics and shape of the object which cannot be got by telemetry data. Using these information, we can contribute to grasp the health. Various methods exist for optical observation, but photometric observation and imaging observation are considered in this research. In this paper, we discuss the estimation of the attitude motion of a space object in the Geostationary region(GEO) using imaging observation. This analysis is based on simulations considering the performance of the AO system and the telescope and atmospheric fluctuation, and proposes the attitude determination method applying the method using computer vision. In the future, we aim at improving the accuracy of dynamic estimation by combining this method with photometric observation and clarifying the system requirements for actual observation.

開催年月日： 2017年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Matsuyama-Ehime   国名：日本国  

This paper gives a thought of using narrow field-of-view telescopes to search fragments from breakups in the geostationary region. The previous studies had proposed an effective search strategy and validated it through observation campaigns. However, when this strategy was applied to a narrow field-of-view telescope, the detection rate was far less than expected. This problem was caused by the coordinate transformation. The previous strategy predicts the population as a function of geocentric right ascension and declination while telescopes need topocentric coordinates. Since each fragment at the observation point has its own geocentric distance, the actual detection rate decreases depending on the geocentric distance selected for the coordinate transformation. Especially, the error largely increases when using narrow field-of-view telescopes. Based on the above facts, this study aims to investigate the change of the detection rate caused by the coordinate transformation and to determine the most effective geocentric distance for the transformation. This study uses a result from the previous study targeting fragments from a US Titan 3C Transtage. Pegasus Observatory at Kyushu University, which has a narrow field-of-view of 0.5 deg, is selected for this study. The result indicates that the effects of coordinate transformation can be decreased when the proper geocentric distance is chosen.

開催年月日： 2017年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Matsuyama-Ehime   国名：日本国  

This paper investigates effects of Lorentz force, induced by interference between geomagnetic filed and charged particles, on orbital evolution of charged particles to understand how Lorentz force changes population of sub-millimeter-size debris. This paper analyzes orbital evolutions of sub-millimeter-size fragments from Fengyun-1C deliberately fragmented in early 2007 in terms of orbital lifetime, position angle and angular separation. The difference of orbital lifetime due to Lorentz force is related with the change of the population in radial direction. Position angle and angular separation provide relative motions of charged particles with respect to uncharged ones in both directions of right ascension and declination. This study will be useful for modeling sub-millimeter-size debris.

開催年月日： 2017年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Matsuyama-Ehime   国名：日本国  

Aiming at applying to an Active Debris Removal (ADR) mission, this work proposes an optimal trajectory design to rendezvous with multiple debris utilizing different nodal regression rates between debris ’and removal satellite ’s orbits. Whereas there are some works treating optimal trajectories to remove multiple debris in LEO considering RAAN changes, this work focuses on spacecraft ’ s transfer orbit that can maximize the effect of the J2 perturbation. Considering that non-coplanar orbital planes for two debris cause relatively high velocity increment to transfer between them, a strategy utilizing different nodal regression rates caused by an orbital perturbation is derived, in which an approach of the RAANs for two debris’ orbits is expected only by waiting for a while. Despite of the effectiveness of the utilization of the orbital perturbation, it is often time-consuming to make use of nodal regressions the debris ’ orbits naturally have. Thus, this work utilizes an additional elliptical orbit, which cannot only be injected into from primary debris ’ orbit easily but also maximize the difference of nodal regression rates between the additional orbit and secondary debris ’orbit. An optimization technique called a Multi-Objective Genetic Algorithm is applied in order to simultaneously improve two different objectives: velocity increment and mission duration, and its effectiveness is finally demonstrated through a numerical experiments based on a priority list of environmentally critical space debris.

開催年月日： 2017年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Matsuyama-Ehime   国名：日本国  

In this paper, effects of electromagnetic fields around the Earth on small space debris is studied. Since the space debris are charged by interacting with the ambient plasma, their motion can be affected by the electromagnetic environment of the Earth. For small space debris, the change in the orbit caused by the electromagnetic perturbing force can be remarkable. Therefore, electromagnetic perturbations on debris should be taken into consideration in order to precisely understand the orbital motion for small space debris. This study aims to construct an orbital model for small debris and offer qualitative understanding of perturbations derived from electromagnetic fields of the Earth.

開催年月日： 2017年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Matsuyama-Ehime   国名：日本国  

Debris mitigation measures such as post-mission disposal (PMD) were set by considering the effects thereof using a debris evolutionary model. Many small satellites have recently been deployed in orbit and various plans are proposed for a so-called mega-constellation consisting of thousands of satellites in Low Earth Orbit (LEO). New systems such as an electric propulsion system and air drag augmentation devices are also proposed for satellite de-orbit. Therefore, the impact of them must be discussed in order to preserve the space environment. This study evaluates the debris mitigation measures taken by using the Near-Earth Orbital Debris Environment Evolutionary Model (NEODEEM) that was jointly developed by Kyushu University and JAXA. It revealed that mega-constellations have much impacts on the debris environment, and that the future environment will be affected by the PMD compliance rate and how PMD is achieved.

開催年月日： 2017年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Matsuyama-Ehime   国名：日本国  

Orbital debris smaller than 1 mm in size still have enough energy to cause a fatal damage on a spacecraft, but such tiny debris cannot be followed or tracked from the ground. Therefore, Kyushu University has initiated IDEA the project for In-situ Debris Environmental Awareness. This project aims to measure the sub-millimeter-size debris with a constellation of small satellites and to establish a dynamic environmental model to be updated continuously. A simple equation that constrains the orbital plane on which debris is detected through in-situ measurements has derived in the previous study by the authors. This study proposes an environmental model that estimates the population of sub-millimeter-size debris from in-situ measurement data with the constraint equation. This paper demonstrates and validates this estimation by impact simulations based upon MASTER-2009. The proposed model was validated that it could estimate the distribution of debris sufficiently. This paper also investigates characteristics of the proposed estimation, which suggest effective strategies to improve the environmental estimation.

開催年月日： 2017年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Matsuyama-Ehime   国名：日本国  

Even sub-millimeter-size debris still could cause a fatal damage on a spacecraft. However, such tiny debris cannot be followed up or tracked from the ground. Therefore, Kyushu University has initiated IDEA the project for In-situ Debris Environmental Awareness, which conducts in-situ measurement of sub-millimeter-size debris. One of objectives is to estimate the location of on-orbit satellite fragmentations from measurements. The previous study derived a constraint equation that applies for the orbital parameters of a broken-up object. The previous study also concluded that two or more measurement satellites are necessary to properly estimate the orbital parameters of the broken-up object based on the constraint equation. This study finds out that even a single measurement satellite can estimate the orbital parameters of the broken-up object in some cases, however. Furthermore, this study derives a new constraint equation that applies for the nodal regression rate of the broken-up object. Finally, this paper demonstrates an effective procedure for a single measurement satellite to estimate the location of on-orbit satellite fragmentations.

開催年月日： 2017年4月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Darmstadt   国名：ドイツ連邦共和国  

Space debris smaller than 1 mm in size still have enough energy to cause a fatal damage on a spacecraft, but such tiny debris cannot be followed or tracked from the ground. Therefore, Kyushu University has initiated IDEA the project for In-situ Debris Environmental Awareness. This project aims to measure the sub-millimeter-size debris with a constellation of small satellites. This study proposes a statistical model that estimates the population of sub-millimeter-size debris using in-situ measurement data. This paper demonstrates and validates this estimation by impact simulations based upon MASTER-2009. This paper also investigates characteristics of the proposed estimation, which suggest effective strategies to improve the environmental estimation.

開催年月日： 2017年2月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：San Antonio, TX   国名：アメリカ合衆国  

Space debris smaller than 1 mm in size still have enough energy to cause a fatal damage on a spacecraft, but such tiny debris cannot be followed or tracked from the ground. Therefore, IDEA the project for In-situ Debris Environmental Awareness, which aims to detect sub-millimeter-size debris using a group of micro satellites, has been initiated at Kyushu University. The IDEA project aims to construct the dynamic environmental model that provides a better defi-nition of the current orbital debris environment. This study proposes data as-similation method to estimate the environment of sub-millimeter-size debris us-ing in-situ measurement data. This paper also verifies the proposed model by simulating the measurement and the estimation. The simulation demonstrates that the estimation model can determine the orbital plane of the detected debris approximately.

開催年月日： 2017年2月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：San Antonio, TX   国名：アメリカ合衆国  

開催年月日： 2016年11月

記述言語：日本語   会議種別：口頭発表（招待・特別）  

開催地：福岡市   国名：日本国  

開催年月日： 2016年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡市   国名：日本国  

開催年月日： 2016年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京都小金井市   国名：日本国  

開催年月日： 2016年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：宇宙航空研究開発機構 調布航空宇宙センター   国名：日本国  

For the sustainable human space development activities, space agencies have developed their own orbital debris environment evolutionary model, projected the debris environmental prediction considering various future scenarios, and studied better mitigation ways. Currently, some companies are developing space broadband network systems and planning to deploy hundreds or thousands of satellites into LEO, which might impose enormous impacts on the debris environment. The influences of such large constellations, called MEGA constellations, are necessary and urgent tasks to be evaluated. In Japan, JAXA and Kyushu University have jointly developed the evolutionary model “NEODEEM”. Present study assumes a large constellation with 1,000 small satellites and evaluates its impacts on the debris environment. The mechanisms of the environmental deteriorations are explained and then various scenarios are simulated and compared to each other.

開催年月日： 2016年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：宇宙航空研究開発機構 調布航空宇宙センター   国名：日本国  

Space debris is the collection of defunct objects made by human being in space. One of the causes of space debris source/sink is space weather (for example, solar flare, solar energetic particle, geomagnetic storm) effect on space debris. To evaluate the effects of long term space weather activities on space debris environmental changes, this study conducts some simulations under different space weather activities using NEODEEM, a Near-Earth Orbital Debris Environment Evolutionary Model. F10.7 and Kp indexes are used as space weather related parameters. As a result, it is found that space debris environment would become significantly worse because of collision cascading even with no launches in the case of low solar activity, like as solar cycle 24.

開催年月日： 2016年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：宇宙航空研究開発機構 調布航空宇宙センター   国名：日本国  

It is important to observe not only the shape and surface characteristic of space objects but also their change over time to correlate them and understand their origin and behavior. In case of objects in low Earth orbit, we cannot track always them. For example, we may lose an object while it is in Earth’s shadow, so that we may need to identify the lost object when it comes up again. Then, estimation of space object behavior using optical measurements is essential to identify it again. Therefore, it is necessary to figure out how space object behavior changes through measurements using medium- and small-aperture telescopes. Space object behavior in optical measurements have been studied for a long time. The imaging correction method using adaptive optics and the attitude and shape estimation method using photometric observation are picked up in this presentation.

開催年月日： 2016年9月

記述言語：英語  

開催地：Guadalajara   国名：メキシコ合衆国  

In this paper, the health of geosynchronous spacecraft is monitored by using light curve observations. For example, whether or not solar paddles are properly deployed, and whether or not the antenna points toward the earth. In order to monitor the health status, an unscented Kalman filter (UKF) is used to estimate rotational states, such as quaternions and angular velocities. Also multiple-model adaptive estimation method is adopted for what?. Running several parallel UKFs, the MMAE method determines the most probable shape of the target spacecraft. Each filter has a different shape model, and the state is computed by the weighted sum of each filter’s estimate. The attitude and shape estimation method is shown in this paper. This study will be useful for checking up the operational states of three-axis stabilized geosynchronous spacecraft in a complex form.

開催年月日： 2016年9月

記述言語：英語  

開催地：Guadalajara   国名：メキシコ合衆国  

The influences of MEGA satellite constellation on the orbital environment are evaluated with the evolutionary model. Walker delta pattern constellation with 1000 satellites on the orbit of 1200 km altitude is assumed as a basic scenario. Various conditions are considered to study the mechanisms of the environmental changes. The constellation satellites can cause the congestion of space debris in two altitude ranges, lower orbit after disposal or initial higher orbit. Population increase in lower orbit affect to the environment for short span, and that in initial higher orbit has impact for long span.

開催年月日： 2016年9月

記述言語：英語  

開催地：Guadalajara   国名：メキシコ合衆国  

This study aims to design realistic multiple space debris removal missions from the perspective of fuel efficiency and environmental remediation. As mission criteria, velocity increment for successive orbit transfers, the expected number of fragments and mission duration are optimized. This study converts a multiple space debris collecting mission to a multi-objective combinational optimization problem. Therefore, the multi-objective genetic algorithm with random weighting methods is adopted to derive pareto optimal solutions. In order to achieve non-coplanar orbital transfer with a smaller velocity increment, the transfer strategy utilizing J2 perturbation via parking orbits is proposed.

開催年月日： 2016年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Maui, HI   国名：アメリカ合衆国  

The 20-kg class microsatellite carrying debris impact sensors IDEA OSG 1 contributes to timely mapping and tracking capabilities for space debris in sub-millimeter size regime are essential to model the low earth orbit (LEO) environment and to improve spaceflight safety. IDEA OSG 1 will sample the sub-millimeter size debris environment in one of the most congested region in LEO by detecting impacts of sub-millimeter size debris and provide key data about the size, the time, and the location of impacted sub-millimeter size debris in near real time.

開催年月日： 2016年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：北海道函館市   国名：日本国  

This paper describes an evaluation and improvement for a scheme to estimate orbital parameters of sub-millimeter-size debris cloud using impact data on measurement satellites. Sub-millimeter-size debris generated from a satellite fragmentation have a greater possibility to collide with measurement satellites on a line of intersection between the debris’ and measurement satellite’s orbital planes. If enough impact data from at least two measurement satellites in different orbits are given, a couple of debris’ orbital parameters, which define their orbital plane, can be efficiently identified. This work evaluates a performance of the proposed scheme based on data of near collision obtained from conjunction analyses, which consider a real break-up event and virtual measurement satellites in orbits. An improvement method of data screening is finally proposed and the effectiveness of the proposed method is demonstrated through error analyses for the measurement data from the numerical simulations.

開催年月日： 2016年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：北海道函館市   国名：日本国  

Space debris is the collection of defunct objects made by human being in space. One of the causes of space debris generation is space weather effect to space debris. In past time, many satellites were broken because of space weather effect, solar energetic particle, atmosphere drag, and so on. NEODEEM (Near-Earth Orbital Debris Environment Evolutionary Model) is the space debris evolutionary model developed by Kyushu University and JAXA. It helps us to evaluate how space weather activities contribute to the space debris environment changes. This paper performs some simulations under different space weather activities on NEODEEM. F10.7 solar flux is used as space weather related parameter. This paper also introduces the effects of space weather activities to long term space debris environment changes.

開催年月日： 2016年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：北海道函館市   国名：日本国  

This paper briefly introduces efforts into space debris modeling towards a better understanding of space debris environment. Space debris modeling mainly consists of debris generation and orbit propagation. Debris generation can characterize and predict physical properties of fragments originating from explosions or collisions. Orbit propagation can characterize, track, and predict the behavior of individual or groups of space objects. Therefore, space debris modeling can build evolutionary models as essential tools to predict the stability of the current or future space debris populations. Space debris modeling is also useful and effective to improve the efficiency of measurements to be aware of the present environment.

開催年月日： 2016年5月

記述言語：英語   会議種別：口頭発表（招待・特別）  

開催地：Jeju   国名：大韓民国  

This paper briefly introduces efforts into space debris modeling towards a better understanding of space debris environment.

開催年月日： 2016年2月

記述言語：日本語  

開催地：名古屋大学   国名：日本国  

開催年月日： 2015年12月

記述言語：日本語  

開催地：北九州市   国名：日本国  

開催年月日： 2015年12月

記述言語：日本語  

開催地：北九州市   国名：日本国  

This paper briefly introduces IDEA the project for In-situ Debris Environmental Awareness, aiming a prompt and clear understanding of the current submillimeter-size debris environment in the low Earth orbit region. Orbital debris, even smaller than 1 mm, may cause a fatal damage on a spacecraft. Therefore, knowledge on submillimeter-size debris should be incorporated in design of spacecraft. However, the current submillimeter-size debris environment has not been defined well because measurements are quite limited in terms of orbital regimes and not continuously available yet. Thus, the IDEA project proposes to deploy a group of micro satellites, which conduct in-situ and near real-time measurements of submillimeter-size debris, into any orbital regimes to be monitored. This paper also introduces a simple constraint equation applicable for orbital planes on which debris contribute to the collision flux that a measurement satellite may experience. Finally, this paper reveals that two measurement satellites or more are necessary to properly estimate the orbital parameters of a broken-up object.

開催年月日： 2015年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：鹿児島県鹿児島市   国名：日本国  

In this paper, a scheme to estimate orbital parameters of debris cloud using impact data on measurement satellites is proposed. Sub-millimeter-sized debris generated from a spacecraft’s breakup event have greater possibility to conflict measurement satellites on a line of intersection between two orbital planes. If enough impact data from at least two measurement satellites in different orbits are given, a couple of debris’ orbital parameters, which correspond to their orbital plane, can be efficiently identified. The effectiveness of the proposed scheme is finally validated through measurement data obtained from a numerical simulation of debris impacts between target debris and two measurement satellites.

開催年月日： 2015年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：鹿児島県鹿児島市   国名：日本国  

The “IDEA project” has been initiated at Kyushu University in 2011 to estimate the environment on sub-millimeter-sized debris that cannot be detected from ground-based observations. A piece of sub-millimeter-sized debris has large kinetic energy enough to cause fatal damage on a spacecraft, so that the environment of sub-millimeter-sized debris must be understood for safe and secure space development and utilization. For this purpose, the project aims to develop the small measurement satellites and construct the in-situ measurement network with satellite constellation. The feasibility study of the first satellite named “IDEA-1” has been conducted at Kyushu University, and now IDEA-1 is in the process of production at ASTROSCALE based on outcome of the feasibility study. This paper describes the outline of space debris issue, history of small satellite development at Kyushu University, IDEA project and IDEA-1. Post IDEA-1 is also considered at Kyushu University. IDEA-1 has two impact sensors to measure only the position of impact with a piece of debris. This paper also discusses what should be included in the post IDEA-1.

開催年月日： 2015年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：鹿児島県鹿児島市   国名：日本国  

Kyushu University established International Centre for Space Weather Science and Education shortly ICSWSE in April 2012. The ICSWSE is leading two major research areas: 1) magnetized environment of the Earth and 2) space debris environment. To contribute to the protection of space environment and space situational awareness the ICSWSE fuses these two major research areas into one new project through a technical and human network established under the MAGnetic Data Acquisition System / Circum pan Pacific Magnetometer Array (MAGDAS/CPMN) project at the ICSWSE. Now the ICSWSE is willing to establish a measurement network for space debris using small-aperture optical telescopes and a small satellite constellation being named DEBris Data Acquisition System / In-situ Debris Environmental Awareness (DEBDAS/IDEA). The telescopes are well organized to be robotically and remotely controlled including sophisticated image processing techniques and orbit estimation software. The satellites are conducting in-situ measurements of micron-size debris using an easy-to-operate new sensor developed at JAXA. Data acquired from the systems will be analyzed and modeled in a manner coupled with space weather science to provide a better understanding of the present and future space environment. The ICSWSE also aims at education for practical astronomy and space engineering at Kyushu University collaborative measurements in combination between robotic telescopes and small satellites space environmental awareness and space science including debris generation and resulting environment. origin identification. Practical astronomy provides you with planning and observation processing and detection and Space engineering provides you with small satellite design production and operation.

開催年月日： 2015年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Maui, HI   国名：アメリカ合衆国  

開催年月日： 2015年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Kobe-Hyogo   国名：日本国  

開催年月日： 2015年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Kobe-Hyogo   国名：日本国  

開催年月日： 2015年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Kobe-Hyogo   国名：日本国  

開催年月日： 2015年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Kobe-Hyogo   国名：日本国  

開催年月日： 2015年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Kobe-Hyogo   国名：日本国  

開催年月日： 2015年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Istanbul   国名：トルコ共和国  

The number of small satellites as those that do not exceed 50kg is rapidly increasing in the low-Earth orbit region. Since the orbital debris mitigation guidelines released by United Nations, Inter-Agency Space Debris Coordination Committee and national space agency does not consider small satellites and typical large satellites separately, small satellites also should conduct post-mission disposal. However most small satellites are launched as piggyback satellites, affordable post-mission disposal of small satellites is different from that of typical large satellites, and this post-mission disposal of small satellites may cause the collisions to other satellites. For developers of small satellites, this paper introduces the effect of small satellites post-mission disposal on sustainable space utilization, which was presented by the authors in previous.

その他リンク： http://dx.doi.org/10.1109/RAST.2015.7208446

開催年月日： 2015年5月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Jeju Island   国名：大韓民国  

開催年月日： 2014年12月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：宇宙航空研究開発機構 調布航空宇宙センター   国名：日本国  

Investigation on the Observation of LEO objects by Small Optical System

開催年月日： 2014年12月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：宇宙航空研究開発機構 調布航空宇宙センター   国名：日本国  

The orbital debris modeling can build evolutionary models as essential tools to predict the current or future orbital debris populations, and also to discuss what and how to do for orbital debris mitigation and environmental remediation. The orbital debris modeling can also devise an effective search strategy applicable for breakup fragments in the geostationary region using ground-based optical sensors, and to evaluate the effectiveness of space-based measurements of objects not tracked from the ground, both to contribute to space situational awareness. Another application of the orbital debris modeling is to estimate attitude motion of space objects to be removed for environmental remediation. This paper briefly introduces efforts into orbital debris modeling and applications.

開催年月日： 2014年12月

記述言語：日本語  

開催地：宇宙航空研究開発機構 調布航空宇宙センター   国名：日本国  

Orbital Object Observation Strategy Based on a Global Weather Model

開催年月日： 2014年12月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：宇宙航空研究開発機構 調布航空宇宙センター   国名：日本国  

Evaluation of the impacts of near-Earth-orbit Debris Removal and Track of Impactful Events' Origin

開催年月日： 2014年12月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：宇宙航空研究開発機構 調布航空宇宙センター   国名：日本国  

Orbital Object Detection Algorithm Using Streaks

開催年月日： 2014年12月

記述言語：日本語  

国名：日本国  

Kyushu University established International Centre for Space Weather Science and Education, shortly ICSWSE, in April 2012. The ICSWSE is leading two major research areas: 1) magnetized environment of the Earth, and 2) space debris environment. To contribute to the protection of space environment and space situational awareness the ICSWSE fuses these two major research areas into one new project through a technical and human network established under the MAGnetic Data Acquisition System / Circum pan Pacific Magnetometer Array (MAGDAS/CPMN) project at the ICSWSE. Now, the ICSWSE is willing to establish a measurement network for space debris using small-aperture optical telescopes and a small satellite constellation, being named DEBris Data Acquisition System (DEBDAS). The telescopes are well organized to be robotically and remotely controlled, including sophisticated image processing techniques and orbit estimation software. The satellites are conducting in-situ measurements of micron-size debris using an easy-to-operate new sensor developed at JAXA. Data acquired from the systems will be analyzed and modeled in a manner coupled with space weather science to provide a better understanding of the present and future space debris environment. The ICSWSE also aims at education for practical astronomy and space engineering at Kyushu University, collaborative measurements in combination between robotic telescopes and small satellites, space environmental awareness and space science, including debris generation and resulting environment. Practical astronomy provides you with planning and observation, processing and detection, and origin identification. Space engineering provides you with small satellite design, production, and operation.

開催年月日： 2014年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡市   国名：日本国  

This paper verifies the feasibility of sensing attitude motion of a rocket body remained in space by using a small satellite not released from the rocket body. satellite can bear up under the space. This paper analyzes the mission by assuming the H-2A upper stage and whether the Especially, the satellite is analyzed in the point of thermal and electrical balance.

開催年月日： 2014年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡市   国名：日本国  

“Space environment observed by telescope” offered at Kyushu University is a practical course to learn astronomical observation and analytical methods for the observational results. In the course, one of the two groups aimed at observing artificial objects such as an artificial satellite and an abandoned rocket body in Earth’s orbit. In this paper, a tracking method to observe artificial objects in Low Earth Orbit (LEO) is described. Then, using image sequences captured on July 11 in 2014, results of an analysis to identify a target object, CZ-3 R/B are shown.

開催年月日： 2014年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡市   国名：日本国  

An educational program of astronomy and space engineering was established by cooperated academic staffs in various fields at Kyushu University since 2011, and related activities have been performed under the title of “Pegasus Project”. The purposes of this project lie in 1) providing interdisciplinary courses under the keyword “the Universe”, 2) practicing of management education using the system of the star guide qualification and contributing to the general public by outreach activities. The interdisciplinary education free from boundaries fixed between academic subjects yielded to broaden interest and to make students understand that academic subjects were linked closely with each other. It was also confirmed that it led students to have high motivation for learning and that it resulted maturing. Furthermore, outreach activities (i.e. visiting lectures and star parties) mainly carried out by qualified students as a star guide were expected not only to render services to the general public but also to promote sociability (ability of planning, presentation and communication) of students themselves. A developed course using a larger telescope is arrange for senior students. Through observations of transient objects (i.e. small solar system bodies and supernovae) or of artificial objects (i.e. satellites and space debris), they learn the technique of scientific and engineering approaches.

開催年月日： 2014年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：長崎県長崎市   国名：日本国  

This paper proposes a new algorithm to detect apparently fast orbital objects by optical observations. The algorithm improves target object’s signal-to-noise-ratio against background by summing signals along expected streak direction. The signal-to-noise-ratio can be improved with proportional to square root of summed pixel number, theoretically. This algorithm is applied to actual observation datasets to confirm its feasibility. The application test results that the algorithm can detect an object appeared on images as streaks even if pixels’ intensity of each streak are weaker than background noise. It indicates that the algorithm can improve efficiency of geosynchronous object survey conducted by JAXA. The algorithm is applied to actual observation datasets to confirm its feasibility. The test results that the algorithm newly detects three detections correlated to two objects. It is also estimated that the darkest result of the three detections is composed of pixels with low signal intensity 0.66.

開催年月日： 2014年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：長崎県長崎市   国名：日本国  

This paper present, method of calculating on original apply to search safety radius of the space elevator cable in the troposphere assuming strong window. The authors can’t write down the detail of experiment due to regulation of the quantity in this paper, but checked the Long column equation whether it was proper. The positive point on this method, can get analytically solution(but wind pressure distribution is idealized).Furthermore, able to clarify the stress properties in the time during reinforced cable, through the figure of analysis results. Then, can estimate an appropriate cable radius at initial cable[1.0mm respond to 1t (cruiser mass)], medium term[3.0mm respond to 10t ], and operative term[9.7mm respond to 30t ].

開催年月日： 2014年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：長崎県長崎市   国名：日本国  

This research intends to build a dynamic model on micron-size orbital debris environment that is updated every time small satellites send impact data to the ground. A piece of micron-size debris can cause fatal damage on a spacecraft because of its high impact velocity. However, measurement data of micron-size debris are quite limited because its size is too small to be observed from the ground. Therefore, we have initiated IDEA the project for in- situ debris environmental awareness to aim to construct an in-situ debris measurement network using a constellation of small satellites. This dynamic model can provide a better definition of the current orbital debris environment to contribute safe and secure space development. For optimization of the satellites constellation and dynamic modeling on micron-size debris environment, this paper investigates the detectability of debris in terms of orbital parameters and time.

開催年月日： 2014年9月 - 2014年10月

記述言語：英語  

開催地：Toronto   国名：カナダ  

This paper proposes an efficient method to detect and track for debris in Geosynchronous Earth Orbit (GEO) using an image sequence and a voting scheme. The proposed method utilizes several motion features appearing in an image sequence which are obtained from a telescope fixed for the azimuth and elevation angles at a certain frame interval. Basically, linear trajectories of debris are detected using line segments which connect candidates of debris in different image frames. The line segments with image displacements over a limit value are removed using a couple of motion prediction techniques for GEO debris. The motion prediction techniques enable us to accelerate the voting scheme based on statistical features on motion direction and displacement computed from the line segments, and finally to detect trajectories of debris while removing ones of stars and noises. The effectiveness of the proposed method　is demonstrated through observation image sequences acquired from the image sensor of the telescope called TAOS in Taiwan.

開催年月日： 2014年9月 - 2014年10月

記述言語：英語  

開催地：Toronto   国名：カナダ  

Kyushu University has initiated a project to understand the current micron-size debris environment by small satellites equipped with impact sensors. The objective of this study is to establish an estimation approach to identify an orbit on which a breakup event occurs using the measurement data from the satellites. This study assumes that two measurement satellites on different earth orbits get impacted with micron-size debris. In addition, this study is based on the presumption that the measurement satellite gets impact data at the line of node intersecting with the orbit of breakup object. This paper focuses on the Chinese anti-satellite missile test in 2007 and the US and Russian satellites accidental collision in 2009 to verify this estimation approach. In this study, a non-linear least squares method is used in order to estimate right ascension of the ascending node and inclination, which define an orbital plane. Using spherical trigonometry (a Napier’s rule), an equation to estimate unknown obital elements is derived. Results from this study confirm that the proposed in-situ measurements technique can identify the orbital plane on which the above breakup events occurred.

開催年月日： 2014年9月 - 2014年10月

記述言語：英語  

開催地：Toronto   国名：カナダ  

This study aims to secure future Earth-to-Moon commercial space travels starting from year 2045. After evaluating risky objects for the mission, the present study focuses on the next step: active debris removal in order to eliminate the related risks. The current proposal consists in launching a mother satellite into the identified objects’ orbital region that corresponds to 600km-800km-altitude range and 82o/98o inclination orbits according to previous results. The mother satellite has a simple cubic shape equipped with six devices (Boys). Each Boy is released from the satellite and attached to one target object. More precisely, this study focuses on the last step of the removal, by trying to analyze and optimize the final approach, the capture, and the de-orbit phases. To optimize the efficiency of the capture phase, the angular velocity, the attitude and the shape of the target have to be considered and evaluated for a better adequacy of the Boy with the object. After its release, the device hits the front side of the target, and according to the impact angle of the device on the target surface, the full adhesion of the boy to the object produces a force that modifies the attitude motion of the target object. To simulate the impact of this adhesive force, the Space Systems Dynamics Laboratory in Kyushu University has developed a complete propagator that associates an orbit propagator to an attitude motion simulator. Indeed, the attitude motion of an object is linked to its orbit motion, due to the mutual coupling effect of orbit perturbations and external torques that change the attitude. Therefore, this propagator allows performing a higher precision estimation for both orbit and attitude motions, which leads to first results concerning the configuration of the target after contact with the Boy. From this estimation, it is possible to evaluate the most adequate point of release for the Boy together with the best timing for the release. Then, de-orbit is operated by 9s-impulse burning from Boy’s thrusters to perform the descent of the target’s orbit. To stabilize this operation, this step is also simulated so as to characterize the impact of the thrust on the object’s motion and the shape of the descent orbit.

開催年月日： 2014年9月 - 2014年10月

記述言語：英語  

開催地：Toronto   国名：カナダ  

Kyushu University has proposed a strategy applicable to optical search and origin identification of fragmentation debris generated by breakups of spacecraft and rocket bodies. This strategy can predict the population and the motion of fragments by using debris modelling techniques. An observation of fragments from a specific breakup was actually conducted by applying the proposed strategy. The target was the US Titan 3C Transtage (1968-081E) exploded in February 1992 in the Geosynchronous Earth Orbit region. In this observation, the Time Delay Integration method was adopted to detect fragments. This method can detect moving faint objects by adjusting a rate of charge transfer in the Charge Coupled Device sensor to their motion on images. In the case of the survey of unknown fragments, the predicted motion can be used as the charge transfer. As the result of this observation, thirty- one unknown objects were detected, and orbit determinations of seven objects have succeeded. The origins of these seven objects were estimated by comparing the estimated orbits with candidates, and one object was identified to the target object. Finally, this paper reviews the proposed search strategy by comparing with the twenty-eight catalogued 1968-081E fragments.

開催年月日： 2014年9月 - 2014年10月

記述言語：英語  

開催地：Toronto   国名：カナダ  

The geostationary region is a unique natural resource that is useful for mankind activities. If accidental collisions take place in the geostationary region, space communities would suffer great inconveniences. Therefore, it is necessary to assess collision risk in this particular region. Kyushu University has developed GEODEEM, an orbital debris evolutionary model, which simulates prolonged debris environment in the geostationary region. GEODEEM calculates the time-averaged probability of collision of a spacecraft with debris. This method cannot properly characterize debris periodically approaching operational spacecraft because the actual position of debris is not considered. Instead, this study adopts “Conjunction Analysis,” so that the relative distance between a spacecraft and debris is computed to evaluate the collision probability at the time of the closest approach. The purpose of this paper is to put forward the necessity of orbital debris removal in the geostationary region by presenting interesting results from “Conjunction Analysis”. Finally, this paper proposes a selection of debris to be removed.

開催年月日： 2014年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Maui, HI   国名：アメリカ合衆国  

Orbital object catalogue maintenance capability should be improved to correspond to future orbital environment because space objects population grows continuously. This paper proposes a follow-up observatory consists of uses of our new image-processing algorithm and the multi-telescope observation method. The algorithm enables to improve SNR of streaks by summing their signal intensities. The observatory applies the algorithm to recover SNR of objects unintentionally appeared as streaks in field of view. However, the improvement capability is limited to a square root of streak length as maximum, theoretically. The proposed observatory uses multi-telescope sets to recover rest of degraded SNR. The feasibility of the algorithm is confirmed by an application test to actual observation datasets. The test resulted that the algorithm enables to detect an object appeared with streaks darker than background noise, e.g. 0.66. This paper summarizes that the observatory can recover observation efficiency degradation due to unintentional appearance as streaks without on-site operation or complex instrument.

開催年月日： 2014年8月

記述言語：英語  

開催地：Moscow   国名：ロシア連邦  

Kyushu University established International Centre for Space Weather Science and Educa- tion, shortly ICSWSE, in April 2012. The ICSWSE is leading two major research areas. One is magnetized environment of the Earth, and the other is space debris environment. Now, the ICSWSE fuses these two major research areas into one new project to contribute to the protection of space environment and space situational awareness. The ICSWSE has already established a technical and human network under the MAGnetic Data Acquisition System / Circum pan Pacific Magnetometer Array (MAGDAS/CPMN) project. Now, the ICSWSE is willing to establish a measurement network for space debris using small-aperture optical tele- scopes and small satellite constellation under the technical and human network, being named DEBris Data Acquisition System (DEBDAS). The telescopes are well organized to be robot- ically and remotely controlled, including sophisticated image processing techniques and orbit estimation software. The satellites are conducting in-situ measurements of micron-size debris using an easy-to-operate new sensor developed at JAXA. Data acquired from the systems will be analyzed and modeled in a manner coupled with space weather science to provide a better understanding of the present and future space debris environment. The ICSWSE also aims at education for practical astronomy and space engineering at Kyushu University, collaborative measurements in combination between robotic telescopes and small satellites, space environ- mental awareness and space science, including debris generation and resulting environment. Practical astronomy provides you with planning and observation, processing and detection, and origin identification. Space engineering provides you with small satellite design, produc- tion, and operation.

開催年月日： 2014年8月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Moscow   国名：ロシア連邦  

This paper proposes an algorithm to detect small or apparently fast orbital objects from optical images making use of their faint streaks. In the conventional algorithm, a high signal-to- background-noise-ratio (e.g., 3 or more) is required to detect objects. In our algorithm, we sum signals along the streak direction to improve sensitivity. By applying this algorithm to multi- images, we can detect lower signal-to-noise ratio objects. The algorithm consists of following steps; 1) take local sums of signal intensity on each pixel along preliminarily predicted streak direction, 2) find middle point candidates of streaks on each image, 3) search candidates of a sequence of points aligning in a straight line, and 4) select the candidate with the best linearity and reliability. In this paper, we focus on objects around geosynchronous orbit where most of streaks are oriented to South-North direction. We note that it is not reasonable to apply this algorithm to low Earth orbit objects having no specific streak direction because of limited computational resources. It requires orbit information from other facilities (e.g., space-based sensors). We confirmed that we can detect a streak appeared on images with approximately 1 signal-to-background-noise-ratio with applying the algorithm.

開催年月日： 2014年5月

記述言語：英語  

開催地：University of Strathclyde, Glasgow   国名：グレートブリテン・北アイルランド連合王国(英国)  

開催年月日： 2014年5月

記述言語：英語  

開催地：University of Strathclyde, Glasgow   国名：グレートブリテン・北アイルランド連合王国(英国)  

開催年月日： 2014年5月

記述言語：英語  

開催地：University of Strathclyde, Glasgow   国名：グレートブリテン・北アイルランド連合王国(英国)  

開催年月日： 2014年3月

記述言語：日本語  

開催地：九州大学西新プラザ   国名：日本国  

開催年月日： 2014年2月

記述言語：日本語  

開催地：福岡市   国名：日本国  

開催年月日： 2014年1月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Santa Fe, NM   国名：アメリカ合衆国  

The paper analyses escape trajectories utilizing lunar gravity assist and unstable manifolds of the Sun-Earth L2 point. There are 4 cases of crossing resulting from the intersection of the manifold tubes associated with the halo orbits and the orbit of the Moon. The 4 crossings have different V-infinity with respect to the Moon. The corresponding lunar gravity assists can result in a range of excess velocities with respect to the Earth. The results can be applied to the design of low-energy escape trajectories as well as the orbit control to bind spacecraft into the Earth system.

開催年月日： 2014年1月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Santa Fe, NM   国名：アメリカ合衆国  

This research aims to secure Earth-Moon travels for common people from 2045. Therefore, the capacity to predict the debris environment along this orbit is required. The idea is to identify the objects that may intersect the transfer orbit in 2045. Collision probability calculation gives the criterion to evaluate this degree of dangerousness in order to decide on the objects that must be removed. However, removal should be performed in advance, on the objects that generate the identified debris. Original debris removal baseline has been set as year 2020 to give enough time to conduct an effective debris remediation process.

開催年月日： 2014年1月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Santa Fe, NM   国名：アメリカ合衆国  

This study investigates abrupt orbital changes, i.e., orbital anomalies of the very old upper-stages Titan Transtages inserted into the geostationary orbit (GEO) region in 1960s and 1970s to find evidences of breakups. The product of the solar reflectivity (Cr) and the area-to-mass ratio (A/m) will be estimated before and after the orbital anomalies of the Transtages. To find evidences of breakups, characteristics of temporal distributions of CrA/m are compared between before and after the orbital anomalies. The known breakup of the Transtage 1968-081E will be utilized as the reference of the comparison study.

開催年月日： 2014年1月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Santa Fe, NM   国名：アメリカ合衆国  

Space System Dynamics Laboratory in Kyushu University has initiated IDEA, the project for In- situ Debris Environmental Awareness to correctly understand current space debris problem. One method selected by IDEA project is using multi-measurement satellites that have a dust impact detector. Latest mission analysis demonstrated that a constellation of measurement satellites is very fruitful to detect micron-size debris. As future action assignments, we are going to analyze how many micron-size debris collide against a dust impact detector on the IDEA satellites and study how we can identify the orbits of breakup objects by using the collision data.

開催年月日： 2014年1月

記述言語：日本語  

国名：日本国  

開催年月日： 2013年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡市   国名：日本国  

Recently, space debris issues draw attention as what is impossible to overlook. However, we have only ground-based observation for space debris. Hence, this paper reveals the dynamics of environmental fluctuation caused by breakup events in order to identify them by using space-based measurements. The result was that maximum collision flux of space debris derived from breakup events is on the parent object’s orbit plane.

開催年月日： 2013年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡市   国名：日本国  

This paper investigates a possibility for a micro satellite to measure the impact velocity of micron-size debris not being tracked from the ground. This paper also establishes a method to determine the orbit of the debris impacted, and evaluates the effect of error in measurement of the velocity on error in orbit determination.

開催年月日： 2013年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡市   国名：日本国  

Kyushu University has established a method of origin identification of fragments from breakups in the geostationary region. This method can identify right origin of uncorrelated targets by comparing measured angular velocity and predicted angular velocity. Ground-based optical survey observations in February 2013, dedicated to possible 1967-066G fragments, have detected 87 uncorrelated targets and successfully followed up 3 uncorrelated targets. This paper explains the above method and the result of its application to these UCTs.

開催年月日： 2013年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡市   国名：日本国  

The geostationary orbit is a unique natural resource that is useful for mankind activities. If accidental collisions occur in the geostationary region, space communities suffer great inconveniences. This paper estimates and evaluates the collision probability between a geostationary satellite controlled to stay at a specified longitude slot and its uncontrolled neighbors. Then this paper also investigates whether or not these uncontrolled neighbors should be removed.

開催年月日： 2013年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：鳥取県米子市   国名：日本国  

The JAXA has been evaluating the risk of the micro-debris impact with spacecraft with regard to ADEOS-II (Midori-II) satellite anomalies. The results showed the damage on the wire harness and other equipment even when the impact of the micro-debris was due to particles in the range of 100um to several millimeters. It is difficult to obtain data on the environment space in required to evaluate the frequency of impact on a satellite by micro-debris, and currently, we are unable to get real-time data. Under these circumstances, it is urgent that environmental data be measured to understand the effect of impact by micro-debris on the safe operation of a satellite and the accurate evaluation of the frequency of these impacts. This paper reports a new-type active dust sensor and a In-situ Observation of Micrometeoroid and Orbital Debris by ELMOS satellite.

開催年月日： 2013年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：鳥取県米子市   国名：日本国  

Developers of small satellites may think of enlarging their effective cross-sectional area to minimize the long-term presence in the low Earth orbit region. However, the enlargement of their effective cross-sectional area causes the temporal increase of cumulative probability of accidental collisions. This paper evaluates the influence of small satellites ppost-mission disposal by enlarging their cross-sectional area on the future population using an orbital debris environment evolutionary model. According to the result of the future projections, the small satellites ppost-mission disposals by enlarging the effective cross-sectional area have the potential risk of increasing the accidental collision. However in the case that small satellites are inserted into orbit below 800 km, the fragments to be generated by collision expected to decay within short term. The effective number of objects below 2,000 km altitude is not different between the case with post-mission disposals and the case without post-mission disposals.

開催年月日： 2013年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：鳥取県米子市   国名：日本国  

This paper proposes Asia-Pacific regional collaboration for long-term sustainability of outer space activities. This regional collaboration aims to establish an orbital debris measurements network using ground-based optical and small aperture telescopes to be deployed in Asia-Pacific region and a group of small satellites detecting micron-sized debris. This measurements network aims at a prompt and clear understanding of the current orbital debris environment. This regional collaboration also offers capacity building in the area of space environmental science and engineering for students and young researches in Asia-Pacific region. Both activities will be cooperated with International Centre for Space Weather Science and Education of Kyushu University.the case with post-mission disposals and the case without post-mission disposals.

開催年月日： 2013年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：鳥取県米子市   国名：日本国  

The Earth orbital environment has been fouled by debris for decades and it is a threat for safe and sustainable space development and its utilization. There are two major countermeasures for this threat; one is protection and the other is collision avoidance. However, current collision avoidance maneuvers may be applicable only for objects larger than 10 cm and it is ten times larger than present maximum of protectable size. This study proposes a collaborative observation between space-based sensors and ground observatories. According to an initial analysis, approximately 10% of small objects in the Low Earth Orbit can be discovered by a single space-based sensor in four years. And it is found that an orbit initially determined by the single space-based sensor has enough accuracy to detect object smaller than 5 cm by ground observatories with assumed specifications.

開催年月日： 2013年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Maui, HI   国名：アメリカ合衆国  

The Earth orbit has been contaminated by artificial objects for decades. Therefore, Space Situational Awareness (SSA) is one of the most important actions for safe and sustainable space development and its utilizations. Orbital objects tracking and maintaining their catalog is the fundament of the activities. To improve the effectiveness of SSA activities, objects tracking capability should be enhanced in terms of applicable size limitation. This paper proposes a collaborative observation method consists of space-based sensors and ground observatories. The proposed method aims to discover and track faint objects in Low Earth Orbit (LEO) by ground observatories using initial orbit estimation result provided by space-based sensors. This follow-up observation is based on an assumption that signal amplification using the image stacking method developed by Japan Aerospace Exploration Agency (JAXA) can be applied to faint LEO objects. However, the applicability of this method is confirmed only for objects in geostationary orbit. Therefore this paper assesses the feasibility of faint LEO object detection using the image stacking method. This paper concluded that the image stacking method based on the space-based observation is applicable for ground observations of LEO objects. And it is also concluded that the proposed ground observatories are able to observe objects smaller than 1 – 5 cm by single 1 m telescope with the image stacking method.

開催年月日： 2013年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Nagoya-Aichi   国名：日本国  

Wireless power transmission is useful in the environment where has difficulty to build electrical equipment. Currently, ground use is enthusiastic; however, space use has wide possibilities, but visualizing utilization is still developing. For future use of wireless power transmission in space, this research tries to clarify the possibility for the necessary equipment verification environment by small satellite. This research takes four steps. First step designs the verification satellite that satisfies the requirement for size, structural strength, mission and operational component, and satellite operation. Second considers the possible experiment contents used by the designed satellite. Third clarifies the requirements according to the contents of experiments. Final step identifies the feasibility of the verification satellite by comparison with demanded requirements and acceptable requirements for verification satellite. This paper mainly indicates about the first step of research. Paper describes the prototype design of verification satellite and experiment contents that can be achieved by the satellite.

開催年月日： 2013年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Nagoya-Aichi   国名：日本国  

Developers of small satellites may think of enlarging their effective cross-sectional area to minimize the long-term presence in the low Earth orbit region. However, the enlargement of their effective cross-sectional area causes the temporal increase of cumulative probability of accidental collisions. This paper evaluates the influence of small satellites’ post-mission disposal by enlarging their cross-sectional area on the future population using an orbital debris environment evolutionary model. According to the result of the future projections, the small satellites’ post-mission disposals by enlarging the effective cross-sectional area have the potential risk of increasing the accidental collision. However small satellites are inserted into orbit below 800 km in this paper, the fragments to be generated by collision expected to decay within short term. The effective number of objects below 2,000 km altitude is not different between the case with post-mission disposals and the case without post-mission disposals.

開催年月日： 2013年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Nagoya-Aichi   国名：日本国  

This paper introduces an effort on going at Kyushu University to precisely describe attitude motion under full orbit perturbations. Five people in total are participating in this effort because of their own objectives. For example, some people apply this effort to understand dynamics of light curve, the change of light intensity or visible magnitude of space objects in optical measurements. Other people apply this effort to conduct a feasibility study of using small satellites to demonstrate wireless power transmission in space. This effort introduces a reference frame being affected by orbit perturbations and the mutual coupling effect of orbit perturbations that generate external torques to change the attitude. This paper focuses on attitude dynamics of a small satellite with relatively low moments of inertia under full orbit perturbations and provides some interesting results and outcome from this effort.

開催年月日： 2013年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Nagoya-Aichi   国名：日本国  

開催年月日： 2013年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Nagoya-Aichi   国名：日本国  

The orbital debris modeling, which describes debris generation and orbit propagation, can build orbital debris evolutionary models as essential tools to predict the current or future orbital debris populations, and also to discuss what and how to do for orbital debris mitigation and remediation. The orbital debris modeling can also devise an effective search strategy applicable for breakup fragments in the geostationary region using ground-based optical sensors, and to evaluate the effectiveness of space-based measurements of objects not tracked from the ground, both to contribute to space situational awareness. Another application of the orbital debris modeling is to estimate attitude motion of space objects to be removed for environmental remediation. This paper briefly introduces efforts being made at Kyushu University in the area of orbital debris modeling and applications.

開催年月日： 2013年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Nagoya-Aichi   国名：日本国  

This paper proposes a method to effectively estimate scales of breakup events in the geostationary region. The proposed method is based on the orbital debris modeling techniques, which describes generation and orbit propagation of debris. Previous methods require orbital parameters resulting from follow-up observations, whereas the proposed method is so practical to require only tracklets in image sequences. The proposed method is designed to revise estimation of a scale of a breakup event used in the breakup model by applying the observation data correlated with the event. Iterating the scale estimation, one can understand the current situation of fragmentation debris environment better in comparison with initial guess situation. Thus, the proposed method will contribute to enhance effectiveness of search strategies for undiscovered fragmentation debris, estimation of current space situations, and prediction of future space situations. As a result of demonstration of the proposed method it is confirmed that estimated scales of several breakup events are converged after iterations by applying actual observation data acquired by optical search surveys. It is concluded that the proposed method can perform as a part of an iterative search strategy for characterizing spacecraft breakup events.

開催年月日： 2013年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Nagoya-Aichi   国名：日本国