研究者業績
基本情報
- 所属
- 国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 准教授総合研究大学院大学 先端学術院 宇宙科学コース 准教授
- 学位
- 博士（工学）(東京大学)
- 研究者番号
- 90836222
- ORCID ID
https://orcid.org/0000-0002-8445-1575- J-GLOBAL ID
- 201801006720467786
- Researcher ID
- GXH-5604-2022
- researchmap会員ID
- B000312477
経歴
5-
2023年4月 - 現在
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2019年3月 - 2023年3月
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2018年4月 - 2019年2月
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2017年6月 - 2017年12月
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2016年10月 - 2016年12月
学歴
3-
2015年4月 - 2018年3月
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2013年4月 - 2015年3月
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2010年4月 - 2013年3月
主要な受賞
7-
2015年3月
論文
59-
Space Science Reviews 220(1) 2024年1月24日 査読有りAbstract Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum $\varDelta $V capability of $600\text{ ms}^{-1}$. Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule.
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Journal of Evolving Space Activities 1 2023年12月 査読有り
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8th IAA Planetary Defense Conference 2023年4月 筆頭著者責任著者
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Acta Astronautica 196 42-56 2022年7月 査読有り筆頭著者責任著者
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The Journal of the Astronautical Sciences 2022年2月4日 査読有り筆頭著者責任著者
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Journal of Guidance, Control, and Dynamics 2022年 査読有り筆頭著者責任著者Asteroid exploration has been attracting more attention in recent years. Nevertheless, we have just visited tens of asteroids, whereas we have discovered more than 1 million bodies. As our current observation and knowledge should be biased, it is essential to explore multiple asteroids directly to better understand the remains of planetary building materials. One of the mission design solutions is utilizing asteroid flyby cycler trajectories with multiple Earth gravity assists. An asteroid flyby cycler trajectory design problem is a subclass of global trajectory optimization problems with multiple flybys, involving a trajectory optimization problem for a given flyby sequence and a combinatorial optimization problem to decide the sequence of the flybys. As the number of flyby bodies grows, the computation time of this optimization problem expands maliciously. This paper presents a new method to design asteroid flyby cycler trajectories utilizing a surrogate model constructed by deep neural networks approximating trajectory optimization results. Because one of the bottlenecks of machine learning approaches is the heavy computation time to generate massive trajectory databases, we propose an efficient database generation strategy by introducing pseudo-asteroids satisfying the Karush–Kuhn–Tucker conditions. The numerical result applied to Japan Aerospace Exploration Agency’s DESTINY+ mission shows that the proposed method is practically applicable to space mission design and can significantly reduce the computational time for searching asteroid flyby sequences.
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EARTH PLANETS AND SPACE 73(1) 2021年12月The science operations of the spacecraft and remote sensing instruments for the Martian Moon eXploration (MMX) mission are discussed by the mission operation working team. In this paper, we describe the Phobos observations during the first 1.5 years of the spacecraft's stay around Mars, and the Deimos observations before leaving the Martian system. In the Phobos observation, the spacecraft will be placed in low-altitude quasi-satellite orbits on the equatorial plane of Phobos and will make high-resolution topographic and spectroscopic observations of the Phobos surface from five different altitudes orbits. The spacecraft will also attempt to observe polar regions of Phobos from a three-dimensional quasi-satellite orbit moving out of the equatorial plane of Phobos. From these observations, we will constrain the origin of Phobos and Deimos and select places for landing site candidates for sample collection. For the Deimos observations, the spacecraft will be injected into two resonant orbits and will perform many flybys to observe the surface of Deimos over as large an area as possible.
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Acta Astronautica 180 679-692 2021年3月
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Journal of Guidance, Control, and Dynamics 43(4) 645-655 2020年3月 査読有り筆頭著者責任著者Recent low-thrust space missions have highlighted the importance of designing trajectories that are robust against uncertainties. In its complete form, this process is formulated as a nonlinear constrained stochastic optimal control problem. This problem is among the most complex in control theory, and no practically applicable method to low-thrust trajectory optimization problems has been proposed to date. This paper presents a new algorithm to solve stochastic optimal control problems with nonlinear systems and constraints. The proposed algorithm uses the unscented transform to convert a stochastic optimal control problem into a deterministic problem, which is then solved by trajectory optimization methods such as differential dynamic programming. Two numerical examples, one of which applies the proposed method to low-thrust trajectory design, illustrate that it automatically introduces margins that improve robustness. Finally, Monte Carlo simulations are used to evaluate the robustness and optimality of the solution.
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Proceedings of the International Astronautical Congress, IAC 2020- 2020年Comet Interceptor, to be launched in 2028, is a recently-selected ESA/JAXA mission aimed to perform the first fly-by of a pristine long-period comet. As part of the mission's Phases A/B (feasibility analysis and preliminary design), this work preliminarily analyzes the attitude performance of JAXA's contribution to the mission, SC B1: one of the two small-spacecraft piggybacked along with ESA's main spacecraft. This study primarily focuses on the characterization of the dust environment, modelization of dust particle impacts, and analysis of attitude performance through the dust environment. Monte Carlo simulations are implemented to assess the performance of the attitude control system within a highly-active dust environment, for various fly-by altitudes and a worst-case 70-km/s fly-by speed. Results evidence the need for a wide-angle camera, and conclude that image acquisition shall tolerate angular velocities of several degrees per second. Solutions for improved attitude performance are also evaluated (i.e., upgrading of reaction wheels and angular momentum pre-loading), and a larger reaction wheels aligned with the camera line of sight is shown to provide largest performance improvements. Such strategies, nevertheless, still result in pointing errors and angular velocities that are only compatible with a short-exposure, wide-angle science camera.
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AIAA Scitech 2020 Forum 1 2020年Low-energy transfers reduce the total ∆V in deep space missions by exploiting multibody dynamics. However, searching for initial guesses in highly nonlinear systems is often a demanding task and it has been heavily dependent on professionals. In this paper, we aim to automate this initial guess search by using deep reinforcement learning (RL) algorithms. Minimum fuel transfer problems from low-Earth orbit to three-body orbits are redefined in the RL framework with the ∆V vector as an action. Since a common RL algorithm, deep deterministic policy gradient, fails to find long time-of-flight transfers, we extend it by explicitly separating a null action from the continuous action space. We demonstrate our algorithm successfully finds long transfers from a wide variety of initial states in both two and three dimensional problems.
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AIAA Scitech 2020 Forum 1 2020年Trajectory design of spacecraft considering probabilistic uncertainties attracts attention for successful missions. Tube stochastic optimal control is proposed to solve this problem, but this theory has not handled situations under imperfect information of spacecraft’s states. This research proposes a novel approach to solve stochastic optimal control problems under imperfect information and applied it to spacing problems of trajectory correction maneuvers. The spacing problem was solved by the proposed method without an assumption of linear dynamics. Numerical simulations illustrate the expected fuel consumption of the optimized solution is less than the solution of the previous research.
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Proceedings of the International Astronautical Congress, IAC 2020-October 2020年Micro/nano-satellite technology development first started as either an educational or research tool primarily at universities and has spread rapidly across the world and found many practical applications. Recent technology advancement has enabled micro/nano satellites to become one of the platforms for deep space science and exploration missions. In order to provide an opportunity for students and researchers worldwide to propose a mission of deep space science and exploration using a micro/nano satellite, the 7th Mission Idea Contest (MIC) will focus on these missions. This is because the technological field of LEO satellites is already well-established, and so we consider that creation of a deep space mission will give the young generation more motivation towards the “Frontier.” MIC has provided aerospace engineers, college students, consultants, scientists, and anybody interested in space with opportunities to present their creative ideas and gain attention internationally. The 7th Mission Idea Contest (MIC7) is to open a door to new opportunities for proposing a deep space mission using a micro/nano satellite. There are several examples and emerging opportunities for micro/nano satellites in these types of missions. In this paper, we briefly introduce the past Mission Idea Contests and present examples of deep space missions using micro/nano satellites for MIC7, and follow this with a discussion on why it is important for UNISEC-Global to organize a “Mission Idea Contest for Deep Space Science and Exploration .
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Proceedings of the International Astronautical Congress, IAC 2020-October 2020年Martian Moons eXploration (MMX) is a mission to Martian moons under development in JAXA with international partners to be launched in 2024. This paper introduces the system definition and the latest status of MMX program. “How was water delivered to rocky planets and enabled the habitability of the solar system?” This is the key question to which MMX is going to answer in the context of our minor body exploration strategy preceded by Hayabusa and Hayabusa2. Solar system formation theories suggest that small bodies as comets and asteroids were delivery capsules of water, volatiles, organic compounds etc. from outside of the snow line to entitle the rocky planet region to be habitable. Mars was at the gateway position to witness the process, which naturally leads us to explore two Martian moons, Phobos and Deimos, to answer to the key question. The goal of MMX is to reveal the origin of the Martian moons, and then to make a progress in our understanding of planetary system formation and of primordial material transport around the border between the inner- and the outer-part of the early solar system. The mission is to survey two Martian moons, and return samples from one of them, Phobos. In view of the launch in 2024, the phase-A study was completed in February, 2020. The mission definition, mission scenario, system definition, critical technologies and programmatic framework are introduced int this paper.
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AIAA Scitech 2020 Forum 1 PartF 2020年© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Solar electric propulsion is a key enabling technology that has improved the efficiency of space transport. With specific impulses that are typically ten times higher than the chemical counterpart, electric motors allow a considerable saving in propellant mass at the expense of longer times of flight. However, the length of the transfer process and the specific operational needs require to develop a different operational concept for the navigation and orbit control that can be sustained during the different phases of the mission. In this paper, a trade-off is performed among several operational concepts and solutions for multi-revolutions SEP transfers with application to the DESTINY+ mission. The GTO-to-Moon low-thrust transfer is first computed in a high-fidelity model with a tangential thrust strategy and later optimized with a five-order Legendre-Gauss-Lobatto collocation method. The impact of eclipses, radiation, thrust outages and misfires, and orbit tracking is analyzed in detailed and included in the transcript optimal problem as algebraic constraints where possible. Numerical results show that the driving factors for the optimal trajectory are related to the operations of the spacecraft rather than the final mass or time of flight.
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Journal of Spacecraft and Rockets 1 PartF 2020年 査読有り筆頭著者
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JOURNAL OF THE ASTRONAUTICAL SCIENCES 67(3) 950-976 2020年1月 査読有りThis paper presents the trajectory design for EQUilibriUm Lunar-Earth point 6U Spacecraft (EQUULEUS), which aims to demonstrate orbit control capability of CubeSats in the cislunar space. The mission plans to observe the far side of the Moon from an Earth-Moon L2 (EML2) libration point orbit. The EQUULEUS trajectory design needs to react to uncertainties of mission design parameters such as the launch conditions, errors, and thrust levels. The main challenge is to quickly design science orbits at EML2 and low-energy transfers from the post-deployment trajectory to the science orbits within the CubeSat's limited propulsion capabilities. To overcome this challenge, we develop a systematic trajectory design approach that 1) designs over 13,000 EML2 quasi-halo orbits in a full-ephemeris model with a statistical stationkeeping cost evaluation, and 2) identifies families of low-energy transfers to the science orbits using lunar flybys and solar perturbations. The approach is successfully applied for the trajectory design of EQUULEUS.
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IEEE Aerospace & Electro. Systems Magazine 2019年11月 査読有り
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33rd Annual AIAA/USU Conference on Small Satellites SSC18(VII-05) 1-5 2019年8月3日 査読有り
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IEEE AEROSPACE AND ELECTRONIC SYSTEMS MAGAZINE 34(4) 38-44 2019年4月 査読有り
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Advances in the Astronautical Sciences 168 281-300 2019年Recent low-thrust space missions have highlighted the importance of designing trajectories that are robust against uncertainties. In its complete form, this process is formulated as a nonlinear constrained stochastic optimal control problem. This problem is among the most complex in control theory, and no practically applicable method to low-thrust trajectory optimization problems has been proposed to date. This paper presents a new algorithm to solve stochastic optimal control problems with nonlinear systems and constraints. The proposed algorithm uses the unscented transform to convert a stochastic optimal control problem into a deterministic problem, which is then solved by trajectory optimization methods such as differential dynamic programming. Two numerical examples, one of which applies the proposed method to low-thrust trajectory design, illustrate that it automatically introduces margins that improve robustness. Finally, Monte Carlo simulations are used to evaluate the robustness and optimality of the solution.
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Advances in the Astronautical Sciences 168 4015-4026 2019年Autonomous orbit determination method using active maneuvers and inter-satellite ranging between multiple spacecraft is applicable to general dynamics situations, but large uncertainty of information about maneuvers results in inaccurate orbit estimation. This paper proposes an accurate and robust estimation method using sequential filter, RTS smoother, and EM algorithm. Proposed method estimates not only states but also maneuver results. Results from simulations of Mars-Phobos system show that the proposed method improve orbits determination accuracy.
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Advances in the Astronautical Sciences 168 301-318 2019年Temporarily-captured orbiters (TCOs) are a new population of asteroids that are temporarily gravitationally bound around the Earth-Moon system. Because of its small geocentric distance and energy, short-term exploration with small Δv is expected possible. This study aims to construct low-energy transfers to 2006 RH120, one of the TCOs, from low-Earth orbit using an analogy with the Earth-Moon low-energy transfers. The initial guess was sought by back-propagating perturbed 2006 RH120’s trajectory, then it was optimized through the direct multiple shooting method. The result shows that various transfers are possible with rendezvous Δv below 100 m/s, and they form diverse family structures.
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Proceedings of the International Astronautical Congress, IAC 2019-October 2019年Copyright © 2019 by the International Astronautical Federation (IAF). All rights reserved. DESTINY+ (Demonstration and Experiment of Space Technology for INterplanetary voYage, Phaethon fLyby and dUSt analysis) is a small-sized high-performance deep space vehicle proposed at ISAS/JAXA. The trajectory design of DESTINY+ is divided into several phases. First phase is an orbit injection into an extended elliptical orbit launched by the Epsilon rocket with the additional solid kick motor. Second phase is many revolutions transfer to raise apogee altitude by low thrust propulsion system to the moon orbit nearby. And at third phase, the distant flyby and the swing-by around the moon is designed to give DESTINY+ momentum to escape Earth gravitational field. At an interplanetary phase, DESTINY+ goes to an Asteroid Phaethon for flyby observation. After the Phaethon flyby, DESTINY+ is planned to go back toward Earth for gravity assist and go to another asteroid 2005UD which thought to have split from Phaethon. This paper discusses DESTINY+'s low-thrust trajectory design. As for the many revolution transfer phase, the low-thrust trajectory is optimized by the multi-objective optimization using genetic algorithm. In this phase, we minimize the time of flight, the passage of time of radiation belt, the work time of low thrust propulsion system and the maximum eclipse period. After the spacecraft reaches to the moon's orbit, it utilizes the moon swing-by several times to connect to the transfer trajectory for Asteroid Phaethon. From these studies, we can show the feasibility of the mission design of DESTINY+,.
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Advances in the Astronautical Sciences 168 653-667 2019年© 2019, Univelt Inc. All rights reserved. The candidate science orbits for two JAXA missions heading to three-body system, EQUULEUS and MMX, are presented in this paper. Both of these missions need to conduct science observations while coping with tight engineering constraints such as thermal and power budgets. Due to these requirements, eclipses may become a significant issue for both missions. To minimize or avoid eclipses, we introduce key design parameters for synodic resonant periodic orbits: the synodic ratio and the elongation angle between the Sun and the two primaries. By combining these parameters, we can obtain science orbits that avoid or minimize eclipses in a full ephemeris model. This approach is demonstrated for the science orbit design of both EQUULEUS and MMX.
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SPACEFLIGHT MECHANICS 2019, VOL 168, PTS I-IV 168 653-667 2019年The candidate science orbits for two JAXA missions heading to three-body system, EQUULEUS and MMX, are presented in this paper. Both of these missions need to conduct science observations while coping with tight engineering constraints such as thermal and power budgets. Due to these requirements, eclipses may become a significant issue for both missions. To minimize or avoid eclipses, we introduce key design parameters for synodic resonant periodic orbits: the synodic ratio and the elongation angle between the Sun and the two primaries. By combining these parameters, we can obtain science orbits that avoid or minimize eclipses in a full ephemeris model. This approach is demonstrated for the science orbit design of both EQUULEUS and MMX.
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SPACEFLIGHT MECHANICS 2019, VOL 168, PTS I-IV 168 4015-4026 2019年 査読有りAutonomous orbit determination method using active maneuvers and intersatellite ranging between multiple spacecraft is applicable to general dynamics situations, but large uncertainty of information about maneuvers results in inaccurate orbit estimation. This paper proposes an accurate and robust estimation method using sequential filter, RTS smoother, and EM algorithm. Proposed method estimates not only states but also maneuver results. Results from simulations of Mars-Phobos system show that the proposed method improve orbits determination accuracy.
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SPACEFLIGHT MECHANICS 2019, VOL 168, PTS I-IV 168 301-318 2019年 査読有りTemporarily-captured orbiters (TCOs) are a new population of asteroids that are temporarily gravitationally bound around the Earth-Moon system. Because of its small geocentric distance and energy, short-term exploration with small Ay is expected possible. This study aims to construct low-energy transfers to 2006 RH120, one of the TCOs, from low-Earth orbit using an analogy with the Earth-Moon low-energy transfers. The initial guess was sought by back-propagating perturbed 2006 RH120's trajectory, then it was optimized through the direct multiple shooting method. The result shows that various transfers are possible with rendezvous Ay below 100 m/s, and they form diverse family structures.
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SPACEFLIGHT MECHANICS 2019, VOL 168, PTS I-IV 168 281-300 2019年 査読有り筆頭著者Recent low-thrust space missions have highlighted the importance of designing trajectories that are robust against uncertainties. In its complete form, this process is formulated as a nonlinear constrained stochastic optimal control problem. This problem is among the most complex in control theory, and no practically applicable method to low-thrust trajectory optimization problems has been proposed to date. This paper presents a new algorithm to solve stochastic optimal control problems with nonlinear systems and constraints. The proposed algorithm uses the unscented transform to convert a stochastic optimal control problem into a deterministic problem, which is then solved by trajectory optimization methods such as differential dynamic programming. Two numerical examples, one of which applies the proposed method to low-thrust trajectory design, illustrate that it automatically introduces margins that improve robustness. Finally, Monte Carlo simulations are used to evaluate the robustness and optimality of the solution.
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東京大学大学院 工学系研究科 航空宇宙工学専攻 2018年3月 査読有り
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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 41(2) 377-387 2018年2月 査読有りLow-thrust propulsion is a key technology for space exploration, and much work in astrodynamics has focused on the mathematical modeling and the optimization of low-thrust trajectories. Typically, a nominal trajectory is designed in a deterministic system. To account for model and execution errors, mission designers heuristically add margins, for example, by reducing the thrust and specific impulse or by computing penalties for specific failures. These conventional methods are time-consuming, done by hand by experts, and lead to conservative margins. This paper introduces a new method to compute nominal trajectories, taking into account disturbances. The method is based on stochastic differential dynamic programming, which has been used in the field of reinforcement learning but not yet in astrodynamics. A modified version of stochastic differential dynamic programming is proposed, where the stochastic dynamical system is modeled as the deterministic dynamical system with random state perturbations, the perturbed trajectories are corrected by linear feedback control policies, and the expected value is computed with the unscented transform method, which enables solving trajectory design problems. Finally, numerical examples are presented, where the solutions of the proposed method are more robust to errors and require fewer penalties than those computed with traditional approaches, when uncertainties are introduced.
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Proceedings of the International Astronautical Congress, IAC 2018-October 2018年Copyright © 2018 by the International Astronautical Federation. EQUULEUS is a Lunar L2 orbiter and a 6-Unit CubeSat by JAXA and the University of Tokyo. OMOTENASHI is a 6-Unit CubeSat by JAXA, the world's smallest Lunar lander. EQUULEUS and OMOTENASHI are among the 13 secondary payloads selected by NASA to be launched with Exploration Mission-1 in 2019. Despite their limited size and cost, EQUULEUS and OMOTENASHI are challenging missions, especially in terms of trajectory design and control. EQUULEUS exploits the Earth-Sun-Moon chaotic dynamics and enter a libration point orbit around the L2 of the Earth-Moon system, using a new water propulsion system with low thrust and little propellant. This “Orbit Control Experiment†is one of the main objectives of the mission. OMOTENASHI executes a semi-hard landing that requires breaking the spacecraft to a stop just a few-hundred meters above the Moon's surface. Both missions present new and unique challenges, where the design of the nominal trajectory is mainly driven by the constrains on orbital control capabilities, and operational and robustness considerations. This paper presents the current baselines, and give an overview of the new techniques developed for their design.
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AIAA Guidance, Navigation, and Control Conference, 2018 (210039) 2018年1月1日 査読有りLow-thrust propulsion is a key technology for space exploration, and much work in astrodynamics presents low-thrust trajectory design methods. Typically, a nominal trajectory is designed in a deterministic system. To account for model and execution errors, mission designers heuristically add margins - for example, by reducing the thrust and specific impulse or by computing penalties for specific failures. These conventional methods are time-consuming, done by hand by experts, and lead to conservative margins. This paper introduces a new method to compute nominal trajectories, taking into account disturbances. The proposed method, tube stochastic differential dynamic programming, is a modified algorithm of stochastic differential dynamic programming to handle the control constraints. The proposed algorithm, which is inspired by the tube model predictive control in the field of robotics, employs the sigma points to create a tube and computes the expected value by the unscented transform. Finally, numerical examples present that the proposed solutions automatically introduce the margin against uncertainty and therefore gain good robustness against uncertainties.
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Proceedings of the International Astronautical Congress, IAC 2018-October 2018年 査読有りCopyright © 2018 by the International Astronautical Federation (IAF). All rights reserved. Martian Moons eXploration (MMX) is a mission under study in ISAS/JAXA to be launched in 2024. This paper introduces the mission design of MMX mission. “How was water delivered to rocky planets and enabled the habitability of the solar system?†This is the key question to which MMX is going to answer. Solar system formation theories suggest that rocky planets must have been born dry. Delivery of water, volatiles, organic compounds etc. from outside the snow line entitles the rocky planet region to be habitable. Small bodies as comets and asteroids play the role of delivery capsules. Then, dynamics of small bodies around the snow line in the early solar system is the issue that needs to be understood. Mars was at the gateway position to witness the process, which naturally leads us to explore two Martian moons, Phobos and Deimos, to answer to the key question. The goal of MMX is to reveal the origin of the Martian moons, and then to make a progress in our understanding of planetary system formation and of primordial material transport around the border between the inner- and the outer-part of the early solar system. The mission is to survey two Martian moons, and return samples from one of them. Following the mission concepts study results presented in the previous conference, the following items will be reported in this paper. First, based on the mission goals and objectives defined, the requirements to the systems and operations are derived and their feasibility is evaluated. Second, as to the key technologies issues identified, partial models are built and their performance is evaluated. And third, collaborations with overseas space agency are discussed and the programmatic framework is defined.
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日本航空宇宙学会論文集 65(6) 219-226 2017年 査読有りEarth observation satellites can improve the flexibility of observation sites by having “maneuverability,” and low-thrust obtained by ion thruster will be a promising method for orbital change for micro-satellites. Designing low-thrust trajectories for these satellites is a multi-revolution and multi-objective (time/fuel-optimal) optimization problem, which usually requires high computational cost to solve numerically. This paper derives an analytical and approximate optimal orbit change strategy between two circular orbits with the same semi-major axis and different local time of ascending node, and proposes a graph-based method to optimize the multi-objective criteria. The optimal control problem results in a problem to search a switching point on the proposed graph, and mission designers can design an approximate switching point on this graph, by using two heuristic and reasonable assumptions that 1) the optimal thrust direction should be tangential to orbit and 2) the optimal thrust magnitude should be bang-bang control with an intermediate coast. Finally, numerical simulation with feedback control algorithm taking thrust margin demonstrates that the proposed method can be applicable in the presence of deterministic and stochastic fluctuation of aerodynamic disturbances.
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SICE Journal of Control, Measurement, and System Integration 10(3) 192-197 2017年 査読有り
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2016 55th Annual Conference of the Society of Instrument and Control Engineers of Japan, SICE 2016 654-659 2016年11月18日 査読有り© 2016 The Society of Instrument and Control Engineers - SICE. This paper presents the planning, flight results and lessons learned of flyby guidance experiments of interplanetary micro-spacecraft PROCYON. PROCYON is the world's first interplanetary micro-spacecraft and was launched on 3rd December, 2014. Orbital control of interplanetary micro-spacecraft is challenging because of severe restriction and lower reliability on spacecraft system. For guidance strategy of PROCYON, we have introduced an innovative guidance strategy by two-stage stochastic programming for thrust-direction-constrained problem. Although the flight experiment has many difficulties especially on navigation, the flight result shows that we successfully demonstrate that PROCYON has been guided to the target point with objective guidance accuracy, which is within 100[km] on B-plane at 3,000,000[km] distance from the Earth. These results contributes the future flyby navigation and guidance for interplanetary micro-spacecraft, which has severe constraints and lower reliability on spacecraft system.
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AIAA/AAS Astrodynamics Specialist Conference, 2016 2016年Solar sail spacecraft is attractive for deep-space exploration since it can control the trajectory without any propellant. On the other hand, it has greater uncertainties in the dynamical system than the conventional spacecraft. Therefore, the solar sail trajectory should be designed with enough robustness against the disturbances. Similarly to the duty cycle in low-thrust trajectory design, a typical method designs a nominal trajectory with an underestimated acceleration model, and controls the solar sail spacecraft to follow the nominal trajectory by shedding the excess thrust in the actual operation. However, this method might be conservative or not robust enough to disturbances. To derive the robust trajectory, this paper introduces Stochastic Differential Dynamic Programming, which solves the quadratically expanded Bellman equation for the stochastic-optimal control problem. Numerical examples show that the proposed trajectories have more robustness to disturbances, and the expected value of performance becomes better.
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Advances in the Astronautical Sciences 158 239-258 2016年This paper proposes a robust-optimal trajectory design method for uncertain system to minimize the expected value of cost-to-go function in Dynamic Programming. The fundamental idea is introducing Stochastic Differential Dynamic Programming (SDDP), which solves stochastic-optimal control problem by the second-order expansion of Bellman's equation around reference trajectory. Most recent studies have focused on trajectory optimization assuming that the spacecraft can control the trajectory perfectly as planed however, the assumption is violated in realistic operations where uncertain events, such as navigation error or uncertainty on dynamical system, perturb the predetermined trajectory. Conventionally, experienced specialists empirically determine "margin" on optimal low-thrust trajectory by duty cycle or forced coast period. A proposed SDDP autonomously provides "margin" in optimization for future feedback as well. Numerical results by V-infinity leveraging problem show that SDDP has "margin" without duty cycle or coast period. Monte-Carlo simulation shows the SDDP solution has better performance than DDP considering uncertainty.
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Proceedings of the International Astronautical Congress, IAC 2016年Copyright © 2016 by the authors. All rights reserved. The Exploration Mission-1 (EM1) is the first test flight of NASA's new Space Launch System. Scheduled for launch in 2018, EM1 will carry the Orion Multi-Purpose Crew Vehicle (MPCV) into a cislunar orbit, together with a secondary payload composed by 13 cubesat. Two of these cubesat are currently proposed by JAXA: EQUULEUS, a 6U Earth-Moon Lagrangian-Point orbiter (in collaboration with the University of Tokyo); and SLSLIM, a 6U Moon lander. This paper presents the mission analysis work for EQUULEUS, while a second paper presents the mission analysis work for SLSLIM. EQUULEUS mission objectives are demonstrating cubesat orbit control techniques within the Sun-Earth-Moon regions; understanding the Earth's radiation environment; characterizing the flux of impacting meteors at the far side of the Moon; and demonstrating future exploration scenarios with a deep-space port at the Lagrange points. Following MPCV disposal, EQUULEUS is separated by the upper stage towards a lunar flyby, which, if not corrected, would result in an Earth escape trajectory. For this reason, after one-day orbit determination a trajectory correction maneuver is performed by the onboard thrusters to pump up the flyby perilune and put the spacecraft into an Moon-return orbit. Exploiting Sun perturbations, multiple lunar flybys and small trajectory correction maneuvers, EQUULEUS will be finally placed into a libration orbit around the Earth-Moon L2 point. We present the trajectory design process and a few sample trajectories, with the current baseline and the launch window analysis. Several astrodynamics techniques are described, including the search for Lunar-return orbits in the Earth-Sun Circular Restricted Three-Body Problem (first introduced by Lantoine in [1], and further developed by Garcia [2] for EQUULEUS and other applications); and the design of Libration orbits and low-energy transfers in real ephemeris.
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IFAC PAPERSONLINE 49(17) 391-396 2016年 査読有りThis paper presents a method to design robust trajectories against possible faults of lover-thrust engines. Recently, increasing number of space probes with love-thrust engines have. been developed. Due to the insufficient reliability of low-trust propulsion system, almost all probes with ion engines have experienced the failure of engines. Conventional methods to design the low-thrust trajectory have pursued fuel minimum solution to only one target celestial body, which does not necessarily mean the maximization of mission achievement. In other words, it Can enhances accomplishment to intelligently change the trajectory when engine failures occur. In this research, the objective function is defined as expected scientific gain and the optimal solution is searched by a proposed method. Resulting method. Bellman Rapidly-exploring Random Trees (Bellman RRT) are efficiently extended by applying the Bellman equation. Finally, the numerical simulation demonstrated that the Bellman RRT improved the mission achievement using real deep space exploration scenario. (C) 2016, IFAC (International Federation Control) Hosting By Elsevier Ltd. All rights reserverd.
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SPACEFLIGHT MECHANICS 2016, PTS I-IV 158 4269-4290 2016年 査読有りWe consider the interplanetary trajectory design problem posed by the 8th edition of the Global Trajectory Optimization Competition and present the end-to-end strategy developed by the team ACT-ISAS (a collaboration between the European Space Agency's Advanced Concepts Team and JAXA's Institute of Space and Astronautical Science). The resulting interplanetary trajectory won 1st place in the competition, achieving a final mission value of J = 146.33 [Mkm]. Several new algorithms were developed in this context but have an interest that go beyond the particular problem considered, thus, they are discussed in some detail. These include the Moon-targeting technique, allowing one to target a Moon encounter from a low Earth orbit; the 1-k and 2-k fly-by targeting techniques, enabling one to design resonant fly-bys while ensuring a targeted future formation plane; the distributed low-thrust targeting technique, admitting one to control the spacecraft formation plane at 1,000,000 [km]; and the low-thrust optimization technique, permitting one to enforce the formation plane's orientations as path constraints.
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SPACEFLIGHT MECHANICS 2016, PTS I-IV 158 239-258 2016年 査読有りThis paper proposes a robust-optimal trajectory design method for uncertain system to minimize the expected value of cost-to-go function in Dynamic Programming. The fundamental idea is introducing Stochastic Differential Dynamic Programming (SDDP), which solves stochastic-optimal control problem by the second-order expansion of Bellman's equation around reference trajectory. Most recent studies have focused on trajectory optimization assuming that the spacecraft can control the trajectory perfectly as planed; however, the assumption is violated in realistic operations where uncertain events, such as navigation error or uncertainty on dynamical system, perturb the predetermined trajectory. Conventionally, experienced specialists empirically determine "margin" on optimal low-thrust trajectory by duty cycle or forced coast period. A proposed SDDP autonomously provides "margin" in optimization for future feedback as well. Numerical results by V-infinity leveraging problem show that SDDP has "margin" without duty cycle or coast period. Monte-Carlo simulation shows the SDDP solution has better performance than DDP considering uncertainty.
MISC
28主要なWorks(作品等)
4主要な共同研究・競争的資金等の研究課題
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日本学術振興会 学術変革領域研究(B) 2020年10月 - 2023年3月
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日本学術振興会 科学研究費助成事業 若手研究 2019年4月 - 2023年3月
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科学技術振興機構(JST) 研究成果最適展開支援プログラム(A-STEP) トライアウト 2020年10月 - 2022年3月
メディア報道
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Tellus 宙畑 2021年11月24日 インターネットメディア人工衛星の軌道を3回に分けて学ぶ連載の最終回。人工衛星でよく使われる軌道についてひとつずつ解説していきます。
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Tellus 宙畑 2021年10月28日 インターネットメディア人工衛星の軌道記事の第2弾！今回はPythonを使って人工衛星の軌道を表現していきます。
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Tellus 宙畑 2021年10月6日 インターネットメディア人工衛星はどのように動いているのでしょうか。人工衛星の軌道解説シリーズ、第一弾は軌道と用途の関係を徹底解説します！
