Publisher：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

Language：English  

DOI： 10.1038/s42004-024-01116-3

Web of Science

PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

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Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

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Scopus

Publisher：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

Scopus

Language：English   Publisher：International Symposium on Space Technology and Science  

<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

Language：English   Publisher：THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

<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

Publisher：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

Publisher：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

Scopus

Publisher：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

Scopus

Language：English   Publisher：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

Language：English   Publishing type：Research paper (scientific journal)  

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

Publisher：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

Language：English   Publishing type：Research paper (scientific journal)  

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

Publisher：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

Publisher：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

Publisher：Journal of Guidance, Control, and Dynamics  

DOI： 10.2514/1.G005961

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

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

Publisher：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

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publisher：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

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Language：English   Publishing type：Research paper (scientific journal)  

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

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Other Link： https://doi.org/10.3389/frspt.2022.867236

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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

Publisher：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

Publisher：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

Language：English   Publishing type：Research paper (scientific journal)   Publisher：THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

<p>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 1 mm 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.</p>

DOI： 10.2322/tastj.20.10

CiNii Research

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Repository Public URL： http://hdl.handle.net/2324/4755253

Publisher：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

Publisher：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

Publisher：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

Publisher：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

Publisher：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

Language：English   Publisher：Space Solar Power Systems Society  

<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

Publisher：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

Language：English   Publishing type：Research paper (scientific journal)  

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

Repository Public URL： http://hdl.handle.net/2324/4741657

Language：English   Publishing type：Research paper (scientific journal)  

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.

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2514/1.G005877

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2514/1.G004966

Repository Public URL： http://hdl.handle.net/2324/4481550

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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.

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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.

Other Link： https://www.onlinejournal.in/IJIRV3I9/127.pdf

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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.

Language：English   Publishing type：Research paper (scientific journal)  

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.

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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

Repository Public URL： http://hdl.handle.net/2324/4402934

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (international conference proceedings)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：Japanese   Publishing type：Research paper (scientific journal)  

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.

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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.

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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.

Language：Japanese   Publishing type：Research paper (scientific journal)  

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.

Language：English   Publishing type：Research paper (scientific journal)  

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.

Language：Japanese   Publishing type：Research paper (scientific journal)  

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.

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

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.

Language：English   Publishing type：Research paper (scientific journal)  

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

Language：English   Publishing type：Research paper (scientific journal)  

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

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DOI： 10.2514/1.11998

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DOI： 10.2514/1.11600

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DOI： 10.1016/j.asr.2003.11.018

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DOI： 10.1016/j.ijimpeng.2003.09.028

Language：Japanese   Publishing type：Research paper (scientific journal)  

Modeling the Orbital Debris Environment

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

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DOI： 10.2514/2.3786

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DOI： 10.1016/S0273-1177(01)00398-2

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DOI： 10.1016/S0094-5765(00)00127-2

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DOI： 10.1016/S0273-1177(99)00004-6

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DOI： 10.1006/jsvi.1996.0390

Language：Japanese  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Event date： 2023.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Sugar Land, TX   Country：United States  

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.

Event date： 2023.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Sugar Land, TX   Country：United States  

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.

Event date： 2023.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Sugar Land, TX   Country：United States  

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.

Event date： 2023.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Sugar Land, TX   Country：United States  

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.

Event date： 2023.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山市   Country：Japan  

Small Satellite Constellation Design for Meso-scale meteorological Phenomena

Event date： 2023.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山市   Country：Japan  

Attitude Control of an Uncooperative Satellite by Laser Ablation

Event date： 2023.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山市   Country：Japan  

Gaussian Process Regression for Photometric Attitude Estimation

Event date： 2023.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山市   Country：Japan  

Close Approach Analysis Method Considering Attitude and Shape with Dual Quaternions

Event date： 2023.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山市   Country：Japan  

An Object Classification Based on Cataloged Objects of Fragmentation Debris　Utilizing EISCAT Observation Data

Event date： 2023.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山市   Country：Japan  

Singular problem and drift stability of space-advertisement formation

Event date： 2023.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山市   Country：Japan  

Relative Orbit Control Under Uncertain Accelerations Using Gaussian Process Regression

Event date： 2023.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Kurume-Fukuoka   Country：Japan  

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.

Event date： 2023.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Kurume-Fukuoka   Country：Japan  

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.

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都調布市   Country：Japan  

A Correlation Analysis between Space Debris Detected by an EISCAT Radar and Cataloged Ones

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都調布市   Country：Japan  

Formation Design for Multi-deorbit Using Laser Ablation

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都調布市   Country：Japan  

Orbit Design for ADR Mission Using Laser Satellite

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都調布市   Country：Japan  

A Study of Utilization and Formulation of Space Debris Index

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都調布市   Country：Japan  

Evaluation of Sustainable Space Development by Considering the Long-term Change in the Upper Atmosphere

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都調布市   Country：Japan  

Analysis of Orbital Debris Environment Using Debris Evolutionary Model

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都調布市   Country：Japan  

Effect of Source Location on Mock-up Satellite Fragmentation

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都調布市   Country：Japan  

Origin Identification of Breakup Event from In-situ Debris Measurements

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Investigation into Fragmentation of the Russian EKRAN 2 Spacecraft

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Stabilization of Space-advertisement Satellite Formation

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

A Correlation Analysis between Objects Detected by an EISCAT Radar and Cataloged Ones

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Effect of Internal Explosion Energy on Satellite Breakup

Event date： 2022.11

Language：Japanese  

Venue：熊本県熊本市   Country：Japan  

Origin Identification of Breakup Event from In-situ Debris Measurements

Event date： 2022.11

Language：Japanese  

Venue：熊本県熊本市   Country：Japan  

Fundamental Research on Explosion Fragmentation Test Methods for A Mock-up Satellite

Event date： 2022.11

Language：Japanese  

Venue：熊本県熊本市   Country：Japan  

Pose Estimation with Dual Quaternions

Event date： 2022.11

Language：Japanese  

Venue：熊本県熊本市   Country：Japan  

Simultaneous Deorbiting of Formation Flying with Non-Cooperative Objects

Event date： 2022.11

Language：Japanese  

Venue：熊本県熊本市   Country：Japan  

Analysis of Satellite Attitude Dynamics by Applying a High-Fidelity Solar Radiation Pressure

Event date： 2022.11

Language：Japanese  

Venue：熊本県熊本市   Country：Japan  

Analysis of Chaotic Orbits in the Earth–Moon Three–Body Problem Using Data–Driven Analysis

Event date： 2022.11

Language：Japanese  

Venue：熊本県熊本市   Country：Japan  

Space Debris Environment in the GEO Regime Viewed from Tomo-e Gozen Data

Event date： 2022.11

Language：Japanese  

Venue：熊本県熊本市   Country：Japan  

Evaluation of Sustainable Space Development with Considering Climate Change

Event date： 2022.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Paris   Country：France  

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.

Event date： 2022.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Paris   Country：France  

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.

Event date： 2022.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Paris   Country：France  

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.

Event date： 2022.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Paris   Country：France  

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.

Event date： 2022.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Paris   Country：France  

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.

Event date： 2022.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Paris   Country：France  

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.

Event date： 2022.2 - 2022.3

Language：English   Presentation type：Oral presentation (general)  

Venue：Beppu-Oita   Country：Japan  

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.

Event date： 2022.2 - 2022.3

Language：English   Presentation type：Oral presentation (general)  

Venue：Beppu-Oita   Country：Japan  

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.

Event date： 2022.2 - 2022.3

Language：English   Presentation type：Oral presentation (general)  

Venue：Beppu-Oita   Country：Japan  

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.

Event date： 2022.2 - 2022.3

Language：English   Presentation type：Oral presentation (general)  

Venue：Beppu-Oita   Country：Japan  

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.

Event date： 2022.2 - 2022.3

Language：English  

Venue：Beppu-Oita   Country：Japan  

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

Event date： 2022.2 - 2022.3

Language：English  

Venue：Beppu-Oita   Country：Japan  

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

Event date： 2022.2 - 2022.3

Language：English  

Venue：Beppu-Oita   Country：Japan  

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

Event date： 2022.2 - 2022.3

Language：English  

Venue：Beppu-Oita   Country：Japan  

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

Event date： 2021.12

Language：English   Presentation type：Oral presentation (general)  

Venue：横浜市港北区   Country：Japan  

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.

Event date： 2021.11

Language：English   Presentation type：Oral presentation (general)  

Venue：online   Country：Japan  

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.

Event date： 2021.11

Language：Japanese  

Venue：山形県山形市（オンライン）   Country：Japan  

A Correlation Analysis for Specific Fragmentation Space Objects Detected via EISCAT Radar

Event date： 2021.11

Language：Japanese  

Venue：山形県山形市（オンライン）   Country：Japan  

Attitude Stabilization of Non-Cooperative Satellite Using Laser Ablation

Event date： 2021.11

Language：Japanese  

Venue：山形県山形市（オンライン）   Country：Japan  

Relative Orbit Estimation of Spacecraft under Unknown Thrust Acceleration

Event date： 2021.11

Language：Japanese  

Venue：山形県山形市（オンライン）   Country：Japan  

Orbit Propagation Accuracy from Earth Shadow Reproduction Point of View

Event date： 2021.11

Language：Japanese  

Venue：山形県山形市（オンライン）   Country：Japan  

Analytic Observability Analysis of Light Curve with Self-Shadowing

Event date： 2021.11

Language：Japanese  

Venue：山形県山形市（オンライン）   Country：Japan  

Selection of Targets to Be Removed with Considering Timeliness

Event date： 2021.11

Language：Japanese  

Venue：山形県山形市（オンライン）   Country：Japan  

Improvement of Orbit Propagation of Space Debris Focusing on Stepper

Event date： 2021.11

Language：Japanese  

Venue：山形県山形市（オンライン）   Country：Japan  

Attitude and Orbit Calculation Using Dual Quaternions

Event date： 2021.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Dubai   Country：United Arab Emirates  

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.

Event date： 2021.6

Language：English   Presentation type：Oral presentation (general)  

Venue：St Petersburg   Country：Russian Federation  

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.

Event date： 2021.2

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都調布市   Country：Japan  

Orbital Debris Modeling in Kyushu Univ.

Event date： 2021.2

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都調布市   Country：Japan  

Overview of Space Debris from Economics

Event date： 2021.2

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都調布市   Country：Japan  

Analysis on Attitude Motion of ADR Target in LEO

Event date： 2021.2

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都調布市   Country：Japan  

Development of JAXA's Original Baseline File for Debris Evolutionary Model

Event date： 2021.2

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都調布市   Country：Japan  

Study of the Environmental Capacity Tolerance of Insertions Using the Orbital Debris Evolutionary Model

Event date： 2021.1 - 2021.2

Language：English   Presentation type：Oral presentation (general)  

Venue：Sydney   Country：Australia  

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.

Event date： 2021.1

Language：English   Presentation type：Oral presentation (general)  

Venue：Virtual Event   Country：Other  

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.

Other Link： https://doi.org/10.2514/6.2021-0559

Event date： 2020.12

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2020.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本市   Country：Japan  

Design of the Spacecraft Rendezvous Orbits for ADR to the Large-scale Space Debris in LEO

Event date： 2020.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：zoom.us   Country：Japan  

Can Space Elevator Survives until its Construction Cost Can Be Recovered?

Event date： 2020.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：zoom.us   Country：Japan  

Event date： 2020.10

Language：English   Presentation type：Oral presentation (general)  

Venue：The CyberSpace Edition   Country：Other  

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.

Event date： 2020.4

Language：English   Presentation type：Oral presentation (general)  

Venue：online   Country：Japan  

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.

Event date： 2020.1

Language：English   Presentation type：Oral presentation (general)  

Venue：Orlando, FL   Country：United States  

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.

Other Link： https://doi.org/10.2514/6.2020-1433

Event date： 2019.12

Language：English  

Venue：Sugarland, TX   Country：United States  

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.

Event date： 2019.12

Language：English  

Venue：Sugarland, TX   Country：United States  

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.

Event date： 2019.12

Language：English  

Venue：Sugarland, TX   Country：United States  

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.

Event date： 2019.12

Language：English  

Venue：Sugarland, TX   Country：United States  

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.

Event date： 2019.12

Language：English  

Venue：Sugarland, TX   Country：United States  

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.

Event date： 2019.12

Language：English  

Venue：Fukuoka-shi   Country：Japan  

Event date： 2019.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本市   Country：Japan  

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.

Event date： 2019.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本市   Country：Japan  

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.

Event date： 2019.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本市   Country：Japan  

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.

Event date： 2019.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本市   Country：Japan  

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.

Event date： 2019.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本市   Country：Japan  

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.

Event date： 2019.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：徳島県徳島市   Country：Japan  

Statistical Analysis on Detection of Environmental Changes of Space Debris utilizing In-situ Measurements

Event date： 2019.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：徳島県徳島市   Country：Japan  

Event date： 2019.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：徳島県徳島市   Country：Japan  

Quantification of satellite mission end risk due to space debris impact

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Washington D.C.   Country：United States  

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.

Event date： 2019.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Washington D.C.   Country：United States  

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.

Event date： 2019.9

Language：English  

Venue：Maui, HI   Country：United States  

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.

Event date： 2019.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都文京区   Country：Japan  

Event date： 2019.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Matsuyama-Ehime   Country：Japan  

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.

Event date： 2018.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

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.

Event date： 2018.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

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.

Event date： 2018.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

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.

Event date： 2018.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

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.

Event date： 2018.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

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.

Event date： 2018.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

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.

Event date： 2018.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本市   Country：Japan  

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.

Event date： 2018.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本市   Country：Japan  

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.

Event date： 2018.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本市   Country：Japan  

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.

Event date： 2018.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡県久留米市   Country：Japan  

An Identification of Space Debris Utilizing EISCAT Radar Observation

Event date： 2018.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡県久留米市   Country：Japan  

Improving Accuracy of Conjunction Assessment using Optical Observation

Event date： 2018.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡県久留米市   Country：Japan  

Event date： 2018.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡県久留米市   Country：Japan  

Attitude and Inertial Property Estimation for an Asymmetric Object

Event date： 2018.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡県久留米市   Country：Japan  

Development of “Q-Li” the CubeSat for Verification of Light-Curve Inversion

Event date： 2018.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡県久留米市   Country：Japan  

Environmental Estimation of Sub-millimeter-size Debris Utilizing In-situ Measurements

Event date： 2018.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Bremen   Country：Germany  

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.

Event date： 2018.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Pasadena, CA   Country：United States  

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.

Event date： 2018.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Pasadena, CA   Country：United States  

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.

Event date： 2017.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Fukuoka-shi   Country：Japan  

Event date： 2017.12

Language：English  

Venue：Fukuoka-shi   Country：Japan  

Event date： 2017.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本市   Country：Japan  

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.

Event date： 2017.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：新潟県新潟市   Country：Japan  

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．

Event date： 2017.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Adelaide   Country：Australia  

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.

Event date： 2017.9

Language：English  

Venue：Adelaide   Country：Australia  

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.

Event date： 2017.9

Language：English  

Venue：Maui, HI   Country：United States  

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.

Event date： 2017.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Matsuyama-Ehime   Country：Japan  

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.

Event date： 2017.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Matsuyama-Ehime   Country：Japan  

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.

Event date： 2017.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Matsuyama-Ehime   Country：Japan  

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.

Event date： 2017.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Matsuyama-Ehime   Country：Japan  

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.

Event date： 2017.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Matsuyama-Ehime   Country：Japan  

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.

Event date： 2017.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Matsuyama-Ehime   Country：Japan  

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.

Event date： 2017.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Matsuyama-Ehime   Country：Japan  

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.

Event date： 2017.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Darmstadt   Country：Germany  

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.

Event date： 2017.2

Language：English   Presentation type：Oral presentation (general)  

Venue：San Antonio, TX   Country：United States  

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.

Event date： 2017.2

Language：English   Presentation type：Oral presentation (general)  

Venue：San Antonio, TX   Country：United States  

Event date： 2016.11

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：福岡市   Country：Japan  

Event date： 2016.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡市   Country：Japan  

Event date： 2016.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都小金井市   Country：Japan  

Event date： 2016.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

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.

Event date： 2016.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

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.

Event date： 2016.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

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.

Event date： 2016.9

Language：English  

Venue：Guadalajara   Country：Mexico  

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.

Event date： 2016.9

Language：English  

Venue：Guadalajara   Country：Mexico  

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.

Event date： 2016.9

Language：English  

Venue：Guadalajara   Country：Mexico  

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.

Event date： 2016.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Maui, HI   Country：United States  

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.

Event date： 2016.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道函館市   Country：Japan  

Evaluation and Improvement of a Determination Method for Sub-millimeter-size Debris Orbital Plane

Event date： 2016.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道函館市   Country：Japan  

Space Debris Environment Changes and Forecasts Associated With Space Weather Activities

Event date： 2016.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道函館市   Country：Japan  

Towards A Better Understanding of Space Debris Environment

Event date： 2016.5

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Jeju   Country：Korea, Republic of  

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

Event date： 2016.2

Language：Japanese  

Venue：名古屋大学   Country：Japan  

Event date： 2015.12

Language：Japanese  

Venue：北九州市   Country：Japan  

Event date： 2015.12

Language：Japanese  

Venue：北九州市   Country：Japan  

IDEA the Project for In-situ Debris Environmental Awareness

Event date： 2015.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鹿児島県鹿児島市   Country：Japan  

A Determination of Debris Orbital Plane Using More Than One Measurement Satellites

Event date： 2015.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鹿児島県鹿児島市   Country：Japan  

Current status and future development of "IDEA" the project to monitor sub-millimeter-sized debris environment using small satellites

Event date： 2015.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鹿児島県鹿児島市   Country：Japan  

Innovative Globalization of Space Weather Science and Education Based on International Observation Network

Event date： 2015.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Maui, HI   Country：United States  

Event date： 2015.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Kobe-Hyogo   Country：Japan  

Event date： 2015.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Kobe-Hyogo   Country：Japan  

Event date： 2015.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Kobe-Hyogo   Country：Japan  

Event date： 2015.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Kobe-Hyogo   Country：Japan  

Event date： 2015.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Kobe-Hyogo   Country：Japan  

Event date： 2015.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Istanbul   Country：Turkey  

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.

Other Link： http://dx.doi.org/10.1109/RAST.2015.7208446

Event date： 2015.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Jeju Island   Country：Korea, Republic of  

Event date： 2014.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

Investigation on the Observation of LEO objects by Small Optical System

Event date： 2014.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

Orbital Debris Modeling and Applications

Event date： 2014.12

Language：Japanese  

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

Orbital Object Observation Strategy Based on a Global Weather Model

Event date： 2014.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

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

Event date： 2014.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

Orbital Object Detection Algorithm Using Streaks

Event date： 2014.12

Language：Japanese  

Country：Japan  

Optical and In-situ Debris Measurements in Collaboration with Space Weather Science and Education

Event date： 2014.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡市   Country：Japan  

Feasibility about Mission Aiming at Sensing Attitude Motion of Rocket Body

Event date： 2014.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡市   Country：Japan  

Observation and Motion Analysis of Artificial Objects in Low Earth Orbit by a Tracking Method

Event date： 2014.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡市   Country：Japan  

Practical Study on General Space Education: Activities of Pegasus Project in Kyushu University

Event date： 2014.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：長崎県長崎市   Country：Japan  

A moving object detection algorithm using faint streaks

Event date： 2014.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：長崎県長崎市   Country：Japan  

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 ].

Event date： 2014.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：長崎県長崎市   Country：Japan  

Dynamic Modeling on Micron-size Orbital Debris Environment

Event date： 2014.9 - 2014.10

Language：English  

Venue：Toronto   Country：Canada  

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.

Event date： 2014.9 - 2014.10

Language：English  

Venue：Toronto   Country：Canada  

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.

Event date： 2014.9 - 2014.10

Language：English  

Venue：Toronto   Country：Canada  

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.

Event date： 2014.9 - 2014.10

Language：English  

Venue：Toronto   Country：Canada  

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.

Event date： 2014.9 - 2014.10

Language：English  

Venue：Toronto   Country：Canada  

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.

Event date： 2014.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Maui, HI   Country：United States  

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.

Event date： 2014.8

Language：English  

Venue：Moscow   Country：Russian Federation  

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.

Event date： 2014.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Moscow   Country：Russian Federation  

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.

Event date： 2014.5

Language：English  

Venue：University of Strathclyde, Glasgow   Country：United Kingdom  

Event date： 2014.5

Language：English  

Venue：University of Strathclyde, Glasgow   Country：United Kingdom  

Event date： 2014.5

Language：English  

Venue：University of Strathclyde, Glasgow   Country：United Kingdom  

Event date： 2014.3

Language：Japanese  

Venue：九州大学西新プラザ   Country：Japan  

Event date： 2014.2

Language：Japanese  

Venue：福岡市   Country：Japan  

Event date： 2014.1

Language：English   Presentation type：Oral presentation (general)  

Venue：Santa Fe, NM   Country：United States  

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.

Event date： 2014.1

Language：English   Presentation type：Oral presentation (general)  

Venue：Santa Fe, NM   Country：United States  

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.

Event date： 2014.1

Language：English   Presentation type：Oral presentation (general)  

Venue：Santa Fe, NM   Country：United States  

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.

Event date： 2014.1

Language：English   Presentation type：Oral presentation (general)  

Venue：Santa Fe, NM   Country：United States  

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.

Event date： 2014.1

Language：Japanese  

Country：Japan  

Event date： 2013.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡市   Country：Japan  

Study about Identification of Breakup Events by Observation of Micron-size Debris Environmental Fluctuation

Event date： 2013.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡市   Country：Japan  

Deliberation of the Method for Measuring Velocity of Micron-size Debris Using Micro Satellite

Event date： 2013.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡市   Country：Japan  

Origin Identification of Uncorrelated Fragments from Breakups

Event date： 2013.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡市   Country：Japan  

Risk Assessment of Collision between Geostationary Satellite and Its Uncontrolled Neighbors

Event date： 2013.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鳥取県米子市   Country：Japan  

In-situ Observation of Micrometeoroid and Orbital Debris by ELMOS

Event date： 2013.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鳥取県米子市   Country：Japan  

Influence of Small Satellites on Sustainable Space Utilization

Event date： 2013.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鳥取県米子市   Country：Japan  

Asia-Pacific Regional Collaboration for Long-term Sustainability of Outer Space Activities

Event date： 2013.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鳥取県米子市   Country：Japan  

Small Orbital Debris Tracking Using Space-based Optical System in Low Earth Orbit

Event date： 2013.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Maui, HI   Country：United States  

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.

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya-Aichi   Country：Japan  

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.

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya-Aichi   Country：Japan  

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.

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya-Aichi   Country：Japan  

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.

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya-Aichi   Country：Japan  

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya-Aichi   Country：Japan  

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.

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya-Aichi   Country：Japan  

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.

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya-Aichi   Country：Japan  

For safe and sustainable space activities, orbital debris environment must be remediated. When active debris removal (ADR) is considered, the target’s attitude motion should be known for a succession of the removal mission. This is because of a way to remove debris by targeting them and exerting some sort of forces on the targets actively. The information on target’s attitude can be estimated from light curves. Indeed, there is a way to observe the attitude directly, but it costs much. As for the way to estimate it from light curves, it cost much less than the former way. However, before working on the estimation, dynamics of the target motion should be revealed as well as how the light curves corresponding to it can be observed. On the other hand, suitable targets of ADR are massive objects since the number of the targets that can be removed during single ADR mission. Thus, this study models the massive object’s motion and the light curves. This paper describes the modeling results and discussions.

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya-Aichi   Country：Japan  

Light curves observation attracts the attention of researchers to investigate and estimate spacecraft’ attitude motion from the measurement because the spacecraft they concern is most likely orbital debris that should be removed for better space environment. This estimation technique is often derived from asteroid’s research. This technique might come into some problems when the technique is applied to objects in low earth orbit because the spacecraft is exposed to different perturbation and disturbance forces that differ from asteroids. Therefore, it is important to model the orbit and the attitude motion very precisely to obtain good estimation. This paper presents that how the light curves change with different perturbations and disturbance forces about a rocket body that is a major target for active debris removal.

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya-Aichi   Country：Japan  

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya-Aichi   Country：Japan  

This paper describes development of a satellite simulator with precise dynamics model including a coupled orbit and attitude motion. In addition, this paper demonstrates orbit determination, attitude determination, and attitude control system from sun sensors model, magnetic sensor model, and gyro model. For attitude controller, magnetic torquers model are installed, and demonstrate two attitude control modes. This simulator will be useful to s small satellite development in Kyushu University, and it is supposed to be used for other application such as ground-based optical observation, and light curve modeling. As an optional support for users, this simulator can visualize its motion using OpenGL.

Event date： 2013.6

Language：English  

Venue：Nagoya-Aichi   Country：Japan  

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya-Aichi   Country：Japan  

The purpose of this research is to estimate as-yet-unknown environment of tiny debris between 100 μm and 1 mm . Because of its high velocity, even though micron size debris, it is quite possible to cause critical damage on spacecraft. It might be a major obstacle to future development of space technology. Therefore, for the safe and secure space developments, ever-growing the importance of provision about micron size debris. However, micron size debris cannot be observed from grand-based sensors because it is too small. Thus, measurement data are very limited. We have to construct a novel measurement system for micron size debris. This paper introduce IDEA the project for In-situ Debris Environmental Awareness that aims to construct an in-situ measurement network using a group of nano satellites and the usage of actual measurement data acquired from IDEA-1 satellite.

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya-Aichi   Country：Japan  

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya-Aichi   Country：Japan  

Event date： 2013.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya-Aichi   Country：Japan  

Event date： 2013.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Nantou   Country：Taiwan, Province of China  

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.

Event date： 2013.5

Language：English  

Venue：Chiba   Country：Japan  

Event date： 2013.4

Language：English  

Venue：Darmstadt   Country：Germany  

Event date： 2013.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Darmstadt   Country：Germany  

Event date： 2013.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Darmstadt   Country：Germany  

Event date： 2013.4

Language：English  

Venue：Darmstadt   Country：Germany  

Event date： 2013.4

Language：English  

Venue：Darmstadt   Country：Germany  

Event date： 2013.4

Language：Japanese  

Venue：東京都文京区   Country：Japan  

Dynamic Modeling on Orbital Debris Environment

Event date： 2013.3

Language：Japanese  

Venue：埼玉大学   Country：Japan  

Event date： 2013.2

Language：English   Presentation type：Oral presentation (general)  

Venue：Kauai, Hawaii   Country：United States  

Orbital debris has become an inevitable problem for the future space exploration, and spacecraft is suggested to remove orbital debris. To fulfill this mission, you need to know target’s attitude motion when installing a mitigation-related device. To support, we developed a simulator of orbit, attitude, and light curve to see how an object behaves. This paper presents a process to simulate virtual rocket body’s observation in LEO assuming an existing telescope in Kyushu University, and to estimate the triaxial ratio, the spin axis, and the shape model. The real observation is supposed to be held in the near future.

Event date： 2013.2

Language：English   Presentation type：Oral presentation (general)  

Venue：Kauai, Hawaii   Country：United States  

This paper aims to characterize a spacecraft explosion event using correlated observations. Outcomes of the characterization measure will enable us to make current space situational awareness accurate, and to predict realistic future space situations. An event to be characterized in this paper is a breakup of the rocket-body Titan 3C Transtage (1968-081E) exploded at 09:31 GMT on 21 February 1992 in the geostationary region. Characteristics to be evaluated include delta-velocity (ΔV) given to each fragment though the event, and a size distribution of the breakup fragments (i.e., the number of fragments generated by the event). This paper also discusses how effective the evaluated characteristics of a breakup event will contribute to re-visiting observation plans for the breakup fragments.

Event date： 2013.1

Presentation type：Symposium, workshop panel (public)  

Venue：福岡アメリカン・センター   Country：Japan  

Orbital Debris Modeling and Applications at Kyushu University

Event date： 2013.1

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

Feasibility study for Space-Based optical observation mission of space Debris

Event date： 2013.1

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

Prediction of Orbital Debris Population with an Orbital Debris Evolutionary Model

Event date： 2013.1

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

R&D on in-situ measurement MMOD sensors at JAXA

Event date： 2013.1

Venue：宇宙航空研究開発機構 調布航空宇宙センター   Country：Japan  

Measurement and modeling of breakup events in the geostationary region

Event date： 2012.12

Venue：Kuala Lumpur   Country：Malaysia  

Event date： 2012.12

Presentation type：Oral presentation (general)  

Venue：Kuala Lumpur   Country：Malaysia  

Event date： 2012.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大分県別府市   Country：Japan  

Overview on Kyushu Earth Observation Satellite QSAT-EOS

Event date： 2012.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大分県別府市   Country：Japan  

Selecting Debris to Be Removed and Their Effectiveness

Event date： 2012.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大分県別府市   Country：Japan  

Space Education for Senior Students using Pegasus Telescope

Event date： 2012.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大分県別府市   Country：Japan  

The Mission Analysis of the Space-based Optical Observation for Orbital Debris

Event date： 2012.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大分県別府市   Country：Japan  

IDEA: In-situ Debris Environmental Awareness

Event date： 2012.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大分県別府市   Country：Japan  

Characteristics of the Venus Earth Gravity Assist (VEGA)

Event date： 2012.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京都   Country：Japan  

Event date： 2012.10

Presentation type：Oral presentation (general)  

Venue：Nalples   Country：Italy  

This paper discusses how we can identify colliding objects to be removed from the low Earth orbit region for sustainable space development and utilization for humankind. Here we compare two different approaches to identify colliding objects to be removed. One approach keeps a view on the possibility of multiple removals. Thus, this approach specifies orbital regions where objects are crowded, and then compares mass between the objects in the crowded region to select candidates. Another approach thinks of impact on the current/future space debris environment. Thus, this approach compares the cumulative probability of accidental collision and/or the expected number of fragments added to the environment due to the accidental collisions to select candidates. Comparison in the effectiveness between the four different approaches in total will be conducted through future projections of the space debris environment in the low Earth orbit region. This paper uses NEODEEM, a space debris evolutionary model for the near Earth orbit region, to conduct this comparison.

Event date： 2012.10

Presentation type：Oral presentation (general)  

Venue：Nalples   Country：Italy