橋本 樹明

This paper discusses landing response control methods of planetary exploration spacecrafts on the basis of momentum exchange principles. Concretely, the methods adopt momentum exchange impact dampers (MEIDs) that absorb the controlled object's momentum with extra masses close to the object (damper masses). For example, this paper shows Upper-MEID (U-MEID) that launches the damper mass upward and Lower-MEID (L-MEID) that drops the damper mass downward. Moreover, Generalized-MEID (G-MEID) consisting of U-MEID and L-MEID is introduced. The optimal design parameters of the G-MEID mechanism in a single-axis case for the landing of a spacecraft are investigated. Simulation investigation verifies that the G-MEID mechanism is superior than any other MEID mechanisms from the point of view of reduction of the maximum rebound of the spacecraft. Moreover, the effectiveness of the G-MEID whose U-MEID adopts an active actuator (G-Hybrid MEID) is verified in the view of the rebound reduction performance and the robustness against the landing ground stiffness and spacecraft's mass variations. © 2012 The Japan Society of Mechanical Engineers.

JAXA is planning exploration missions to the moon, following upon the Kaguya (SELENE) mission., These missions aim to demonstrate some new technologies, observe the moon scientifically, investigate technical, social and political feasibility of utilizing the moon. For the first step of the missions, the phase A study of SELENE-2 has started from the summer of 2007. This mission will demonstrate the effectiveness of several technologies including precision landing, hazard avoidance, surface mobility, and night survival technologies. In situ geological and geophysical observations will be conducted to improve our knowledge on the origin and the evolution of the moon. Investigating the lunar surface conditions and its potential for in situ resource utilization will provide key information for future human exploration missions. This paper presents the current status of the SELENE-2 mission, its objectives, its design, and other important aspects of its development such as international cooperation. (C) 2010 Elsevier Ltd. All rights reserved.

JAXA is planning moon exploration missions following Kaguya (SELENE), whose missions include technology demonstrations, scientific observations, investigations for future moon utilization, and social or political purposes. SELENE-2 is the first Japanese moon lander and its phase-A study started in the summer of 2007. SELENE-2 will demonstrate precision landing, hazard avoidance, surface mobility, and night survival technologies. In-situ geological and geophysical observations will contribute to improve the knowledge on the origin and the evolution of the moon. Investigations of surface environment and possible in-situ resource will be useful for future human exploration. In this paper, recent progress of research and development for SELENE-2 is presented.

JAXAでは「かぐや」に続く月探査ミッションとして月惑星への着陸および移動探査技術の獲得を主目的としたSELENE-2計画を検討している,現在はフェーズA(プリプロジェクト)段階にあり,2010年代半ばの打ち上げを目指している.本稿ではSELENE-2ミッションの現状と今後の動向について紹介する.

はやぶさ探査機による小惑星イトカワ表面の画像から小惑星表面の巨礫の組織観察を行うことができた.イトカワ表面の巨礫は,大まかにいって不均質な破壊強度を持つものと,均質な破壊強度をもつものに分けられる.前者は角礫岩と考えても矛盾はない.一方,後者の組織は一般的なLLコンドライトには見られない.衝撃によってかなり溶融した普通コンドライト隕石は,そうでないものよりも均質でより高い破壊強度を持つことを考慮すると,後者の巨礫はそのような隕石と類似の岩質をもつかもしれない.これらの巨礫はイトカワの祖先天体で形成されたと考えられる.高解像度画像は小惑星の地史を検討する手段として非常に有効である.

JAXA is planning moon exploration missions following Kaguya (SELENE), whose missions include technology demonstrations, scientific observations, investigations for future moon utilization, and social or political purposes. As the next step of moon mission, SELENE-2 is planed and phase-A study of it has been conducted since the summer of 2007. SELENE-2 will demonstrate precision landing including hazard avoidance, surface mobility, and night survival technologies. For science, in-situ geological and geophysical observations are essential to improve the knowledge on the origin and the evolution of the moon. Investigations of surface environment and possible in-situ resource will contribute future human exploration. International coordination and contribution arc also important aspect of SELENE-2. In this paper, recent study status of SELENE-2 is presented.

In lunar and planetary exploration, a spacecraft is required to select and land in a safe area autonomously. For this purpose, hazard recognition, and obstacles detection methods using a three dimension elevation map constructed from laser range data has been proposed. However, the hardware of laser sensor is generally heavy, consumes a lot of power, and requires a long time to scan a large area. On the other hand, a camera is relatively small and has lower power consumption. Therefore, we propose a method of hazard recognition by using shadows, terrain features, and a priori information such as sun angle or geological knowledge of an image, without the need to construct a three dimensional elevation map. The method detects obstacles like craters and rocks the same way that human intuitively finds obstacles. Concretely, the method detects the edge of the obstacles (such as craters and ridge) by spatial difference of brightness obtained from an image. From shadow and sun light direction, some obstacles like large rocks and craters can be detected. The paper shows the effectiveness of the proposed method by simulation. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

JAXA has been developing a system to provide a long duration, good quality microgravity environment based on a capsule, named the Balloon-based Operation Vehicle, that can be released from a balloon. In this paper we will describe the Balloon-based operation vehicle itself and the experiments using GPS performed - in cooperation with Delft University of Technology - on the gondola of the balloon in 2008 (single baseline estimation) and 2009 (full attitude determination and relative positioning). The attitude calculated using raw observations from a GPS receiver during the 2009 experiment is compared with Sun Aspect Sensors' and Geomagnetic Aspect Sensor's results and moreover with the attitude as provided by the receiver itself.

JAXA is planning moon exploration missions following Kaguya (SELENE), whose missions include technology demonstrations, scientific observations, investigations for moon utilization, and social or political purposes. For the first step of moon landing missions, SELENE-2 is planed and phase-A study of it has been conducted since the summer of 2007. SELENE-2 will demonstrate precision landing including hazard avoidance, surface mobility, and night survival technologies. For science, in-situ geological and geophysical observations is essential to improve the knowledge on the origin and the evolution of the moon. Investigations of surface environment and possible in-situ resource will contribute future human exploration. International coordination and contribution are also important aspect of SELENE-2. In this paper, present study status of SELENE-2 is presented.

A Magnetic Bearing Wheel (MBW) with inclined magnetic poles has been developed. This paper deals with dynamics interaction between a satellite and the MBW. In the MBW-satellite system, the MBW rotor is coupled with the satellite by magnetic bearing forces and torques and there is some possibility that the magnetic bearing controller makes the satellite nutation unstable. In this paper, equations of motion of the MBW-satellite system are formulated by Kane's method and based on the stability analysis of this system, it is shown that both cross feedback control of rotor gimbal angle and integrator in the ordinary magnetic bearing controller are instability factors of the satellite nutation. However, this nutation is stabilized with cross feedback control of the satellite angular rate estimated by a minimal order observer from the magnetic bearing control torques. The effects of the disturbance feedback controller in our 3rd report on the system stability are also considered, and the results show that the system stability is not affected by the disturbance feedback controller.

Recent advances in the characterization of small body surfaces with stereophotoclinometry are & discussed. The principal data output is an ensemble of landmark maps (L-maps), high-resolution topography/albedo maps of varying resolution that tile the surface of the body. Because they can have a resolution comparable to the best images, and can be located on a global reference frame to high accuracy, L-maps provide a significant improvement in discriminatory power for studies of small bodies, ranging from regolith processes to interior structure. These techniques are now being used to map larger bodies such as the Moon and Mercury. L-maps are combined to produce a standard global topography model (GTM) with about 1.57 million vectors and having a wide variety of applications. They can also be combined to produce high-resolution topography maps that describe local areas with much greater detail than the GTM. When combined with nominal predictions from other data sources and available data from other instruments such as LIDAR or RADAR, solutions for the spacecraft position and camera pointing are the most accurate available. Examples are drawn from studies of Phobos, Eros, and Itokawa, including surface characterization, gravity analysis, spacecraft navigation, and incorporation of LIDAR or RADAR data. This work has important implications for potential future missions such as Deep Interior and the level of navigation and science that can be achieved. © The Meteoritical Society, 2008.

A Magnetic Bearing Wheel (MBW) with inclined magnetic poles which is composed of six electromagnets and six displacement sensors and enables a 5-DOF magnetic bearing, has been developed. This paper deals with equations of motion of the MBW. In general, these equations are formulated in consideration of only the rotor imbalance. However, besides the imbalance, there are actually other disturbance factors in the magnetic bearing and the ordinary equations are difficult to simulate the actual disturbance properties of the MBW. In this paper, the more accurate equations of motion of the MBW are formulated in consideration of all disturbance factors of the MBW including property differences among six electromagnets. In addition, the accuracy of the proposed equations is verified by the coincidence of simulation and experimental results.

衛星に搭載された太陽センサーは出来るだけ精度良く太陽方向を測定し,その信号は衛星の姿勢安定化に使用される.「ひので」(Solar-B)衛星に搭載された望遠鏡は今までにない高い角分解能で太陽を観測する装置であり,衛星には極めて高い姿勢安定化が要求された.このために,我々は,ランダム誤差1 秒角(3σ),±0.5 度視野にわたりバイアス誤差2 秒角(p-p)という高い位置決定精度で太陽方向を測定することができる超高精度太陽センサー「UFSS」を開発した.性能検証モデル品を用いて高精度計測を可能とする手法を確立し,フライトモデル製作に向けた性能検証を行い,フライト品設計に反映させた.また確立した計測手法を用いてフライト品の性能検証を行った.

ドラッグフリー技術に基づいた新しい自由落下カプセルを,2006年5月に高高度気球B200を用いて高度40km から投下し,微小重力実験が行われた。今回の最初の試験飛行により,三陸大気球観測所の制御室とカプセルとの間での無線通信,ドラッグフリー制御,そして飛行シーケンスを分析するための基本的データを得ることに成功した.

The second flight of microgravity experiment system using a free fall capsule from a high altitude balloon was conducted in May 2007. Using a drag free control, around 10(-4) G gravity conditions were obtained for 30 seconds. Results of a combustion experiment with Japanese sparker conducted inside the microgranity experimental unit were also reported

Hayabusa spacecraft performed the final descents and touchdowns twice in November 2005. In final descent phase, terrain alignment maneuvers were accomplished to control both altitude and attitude with respect to the surface by using four beams Laser Range Finder onboard. Then Hayabusa spacecraft made dynamic touchdowns the surface of the asteroid by the sampler system to collect samples automatically. This paper presents the terrain alignment maneuver and touchdown scheme. This paper also describes the novel sample horn system and touchdown dynamics. Touchdown tests on the ground are presented. Then the flight results on descent and touchdown dynamics are shown and discussed.

Rocket-shaped vehicle is developed to conduct microgravity experiment by dropping from the high-altitude balloon. Its design strategy and development status is introduced. Also, the result of its 2nd flight test is summarized to show the feasibility of the balloon-based microgravity experiment.

For astronomical observing missions by formation flying satellites in LEO, satellites require control force to keep the relative position, against Keplerian orbit in an inertia coordinate frame. Since satellites require propulsion systems, i.e. thrusters, but the use of thrusters limits the mission lifetime associated with the finite fuel supply. Thus the authors propose the formation flight using electromagnetic force. In this method, the electromagnetic force between super-conducting magnets are used for the relative position control. This method has the obvious advantage of no-fuel to acquire control force. Since such large magnetic moment in earth magnetism generates large disturbance torque, the magnetic moments should be sinusoidal with shorter period than that of the orbit period. Therefore, this paper proposes the relative position control by changing the phase difference between sinusoidal magnetic moments. The proposed method was evaluated with numerical simulations and the results shows the feasibility of the proposed formation flight.

MUSES-C mission is the world first sample and return attempt to or from a near-Earth asteroid. In deep space, it is hard to navigate, guide and control a spacecraft on a real-time basis remotely from the earth, mainly due to the communication delay. Thus, autonomy and robotics technologies are required for final approach and landing to an unknown body. In the final descent phase, cancellation of the horizontal speed relative to the surface of the landing site is essential. During the touchdown and sampling phase, the spacecraft will be navigated relative to the asteroid surface using an optical target marker (TM) placed on the asteroid surface. By using the TM as a reference point, navigation during the landing phase will be much more reliable and precise. Thus, it is important to design a TM with as small a coefficient of restitution as possible to reduce the settling time. To develop a small coefficient of restitution of less than 0.1 in vertical direction, the authors propose a novel TM, which is constructed out of a shell with beads stored internally. To better predict the performance of such a TM, analytical and numerical investigations are performed. The validity and the effectiveness of the proposed method are confirmed and evaluated by numerical simulations and flight results. © 2007 VSP.

The Hinode satellite (formerly Solar-B) of the Japan Aerospace Exploration Agency's Institute of Space and Astronautical Science (ISAS/JAXA) was successfully launched in September 2006. As the successor to the Yohkoh mission, it aims to understand how magnetic energy gets transferred from the photosphere to the upper atmosphere and results in explosive energy releases. Hinode is an observatory style mission, with all the instruments being designed and built to work together to address the science aims. There are three instruments onboard: the Solar Optical Telescope (SOT), the EUV Imaging Spectrometer (EIS), and the X-Ray Telescope (XRT). This paper provides an overview of the mission, detailing the satellite, the scientific payload, and operations. It will conclude with discussions on how the international science community can participate in the analysis of the mission data. © 2007 Springer Science+Business Media B.V.

A new feedforward algorithm for flexible spacecraft maneuvers is presented. We call this preshaping profiler the nil-mode-exciting (NME) profiler. This algorithm is designed particularly for single-axis rest-to-rest rotational maneuvers (switching maneuvers) with linear actuators. Generally spacecraft with large flexible structure has a lot of large-mass flexible-modes. Therefore, uncertainity of high-order modes needs to be considered for high-accuracy controller design. This paper presents an extrainsensitive maneuvering method which overcomes above-mentioned difficulties. This algorithm includes a preshaping profiler formulated from sampling function (also known as sinc function), consequently feedforward control inputs generated from the preshaping profiler have no frequency response above a certain designed frequency. Therefore residual vibration at the end-point of maneuver can be highly reduced with minimum loss of maneuver agility. Copyright © 2007 IFAC.

Reported in this paper is the initial phase operation of the attitude and orbit control system (AOCS) of Japanese satellite "AKARI". AKARI is the first Japanese satellite dedicated to the infrared astronomy. AKARI was successfully launched by M-V rocket from Kagoshima Space Center on February 22, 2006. Just after the launch, AKARI faced to a serious problem. It was found that something interferes with the fields of view of two (out of two) sun sensors. The two sensors were out of use in the subsequent AOCS operation. Fortunately, by using two star trackers and gyros, the attitude accuracy required for the scientific observation can be achieved without the sun sensors. However, as other many satellites, the sun sensors were to play important roles in AKARI's AOCS operation. Firstly, they were to be used for sun acquisition at the very initial phase. The anomaly prevented us from carrying out the pre-planned sequence. However, the crisis was overcome with the appropriate ground support operation. Secondly, for the observation in far infrared wavelength, the telescope and the scientific instruments of AKARI are stored in the cryostat and cooled by liquid Helium. To prevent the sun light inflow to the telescope, the attitude of AKARI against the sun is strictly constrained after the scientific observation starts. The sun sensors were to be used to watch the sun direction to keep the appropriate attitude against the sun even when AKARI falls into the safe mode. To save the cryostat from the sun light in the absence of the sun sensors, AOCS architecture was reconfigured so that the equivalent function is achieved by the remaining sensors. The experiences in this recovery operation are mainly reported in this paper. In addition, unexpected continuous orbit rising was observed in the operation. The cause of the phenomenon and the investigation process are also reported.

Reported in this paper is the initial phase operation of the attitude and orbit control system (AOCS) of Japanese satellite "AKARI". AKARI is the first Japanese satellite dedicated to the infrared astronomy. AKARI was successfully launched by M-V rocket from Kagoshima Space Center on February 22, 2006. Just after the launch, AKARI faced to a serious problem. It was found that something interferes with the fields of view of two (out of two) sun sensors. The two sensors were out of use in the subsequent AOCS operation. Fortunately, by using two star trackers and gyros, the attitude accuracy required for the scientific observation can be achieved without the sun sensors. However, as other many satellites, the sun sensors were to play important roles in AKARI's AOCS operation. Firstly, they were to be used for sun acquisition at the very initial phase. The anomaly prevented us from carrying out the pre-planned sequence. However, the crisis was overcome with the appropriate ground support operation. Secondly, for the observation in far infrared wavelength, the telescope. and the scientific instruments of AKARI are stored in the cryostat and cooled by liquid Helium. To prevent the sun light inflow to the telescope, the attitude of AKARI against the sun is strictly constrained after the scientific observation starts. The sun sensors were to be used to watch the sun direction to keep the appropriate attitude against the sun even when AKARI falls into the safe mode. To save the cryostat from the sun light in the absence of the sun sensors, AOCS architecture was reconfigured so that the equivalent function is achieved by the remaining sensors. The experiences in this recovery operation are mainly reported in this paper. In addition, unexpected continuous orbit rising was observed in the operation. The cause of the phenomenon and the investigation process are also reported.

This paper proposes a new micro gravity experimental system called BOV (Balloon-based Operation Vehicle). BOV uses a free-fall capsule with double-shell structure to prevent influence of aerodynamic disturbance. Additionally, BOV is raised to 40km by a high altitude balloon to extend micro gravity duration to 30(or possibly 60) seconds. Thus we realize a medium duration micro gravity system with good micro gravity environment. In this system, the most characteristic point is double-shell structure. The inner shell can fall freely since the outer shell measures the relative position with laser displacement sensors and is controlled by gas-jet thrusters not to collide the inner shell. Therefore the inner shell can be uninfluenced of the dynamic pressure and other aerodynamic disturbances ideally. The BOVs project has run since 2004. The first flight to check the whole system was accomplished in 2006. The aim of this flight was test of a high altitude balloon, communication and data handling system, control system, onboard electronics and operation. The second flight expected to achieve 30 seconds micro gravity was also accomplished on May in 2007. This paper presents the development of BOV's control system and shows the experimental results of micro gravity and consideration for effectiveness of the proposed system. Copyright 2007 by the IAF or the IAA. All rights reserved.

Hayabusa was moving near Asteroid Itokawa for about three months in 2005. Using tracking and navigation data such as range, Boppler, distance from the asteroid, and optical images taken by navigation cameras, we estimated the mass of Itokawa for several orbital phases. The results are consistent in their error ranges. The estimated mass of Itokawa is 3.51 ± 0.105 (1010 kg), from which the density of Itokawa is derived as 1.9 ± 0.13 (g/cm3). This is one of the important characteristics to understand the nature of Itokawa. We are also trying to investigate the accuracy of the ephemeris of this asteroid. Copyright © 2006 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Rendezvous of the Japanese spacecraft Hayabusa with the near-Earth asteroid 25143 Itokawa took place during the interval September through November 2005. The onboard camera imaged the solid surface of this tiny asteroid (535 meters by 294 meters by 209 meters) with a spatial resolution of 70 centimeters per pixel, revealing diverse surface morphologies. Unlike previously explored asteroids, the surface of Itokawa reveals both rough and smooth terrains. Craters generally show unclear morphologies. Numerous boulders on Itokawa's surface suggest a rubble-pile structure.

The locations of the pole and rotation axis of asteroid 25143 Itokawa were derived from Asteroid Multiband Imaging Camera data on the Hayabusa spacecraft. The retrograde pole orientation had a right ascension of 90.53° and a declination of -66.30° (52000 equinox) or equivalently 128.5° and -89.66° in ecliptic coordinates with a 3.9° margin of error. The surface area is 0.393 square kilometers, the volume is 0.018378 cubic kilometers with a 5% margin of error, and the three axis lengths are 535 meters by 294 meters by 209 meters. The global Itokawa revealed a boomerang-shaped appearance composed of two distinct parts with partly faceted regions and a constricted ring structure.

A Magnetic Bearing Wheel (MBW) with inclined magnetic poles is under development. This paper deals with the analysis of disturbance factors and motion of MBW. In general, disturbance factors of a magnetic bearing is limited to rotor imbalance, and motion of the magnetic bearing is discussed under the action of synchronous disturbance force/moment caused by the imbalance. This imbalance is defined by the radial shift (static imbalance) and tilt (dynamic imbalance) of sensor detection surface against the principal inertial axis of rotor. However, besides the imbalance, there are actually other disturbance factors such as the radial shift and tilt of rotor core surface similar to sensor detection surface, and the distortion of those surfaces so that MBW generates synchronous and harmonic disturbances. In this paper, all disturbance factors of MBW is formulated, and the relation between each factor and disturbance force/moment is clarified. Moreover, it is clarified that there are forward and backward components to the direction of rotor spin in radial harmonic disturbances.

A Magnetic Bearing Wheel (MBW) with inclined magnetic poles is under development. This paper deals with the low disturbance control method of MBW based on the disturbance feedback. This control method generates the rotor displacement command that converges synchronous and harmonic components included in the disturbance of MBW to zero. This control system can be stabilized by adding appropriate phase lead as a function of the rotational speed of the rotor to the rotor displacement command. Based on the stability analysis by root loci, a simple adjusting method of the phase lead parameters is proposed. Next, the effectiveness of this control method is verified by the numerical simulation and the experiment. This control system enables the disturbance of MBW to decrease to 0.1 N_<rms>/0.045 Nm_<rms> or less in all rotational speeds up to 6000 rpm.

A new feedforward algorithm for flexible spacecraft maneuvers is presented. This algorithm is designed particularly for single-axis rest-to-rest rotational maneuvers (switching maneuvers) with linear actuators. Generally spacecraft with large flexible structure has a lot of large-mass flexible-modes. Therefore, uncertainty of high-order modes needs to be taken into consideration for high-accuracy controller design of large flexible spacecraft. Most researcher propose algorithms of which target flexible-modes are finite number and narrow tolerances, so control errors are inevitable if applied to a large flexible satellite. This paper presents an extra-insensitive maneuvering method which overcomes above-mentioned difficulties. Angular acceleration profile which has a shaped frequency characteristic is computed from 'desired maneuver angle' and 'desired maneuver time' by the algorithm. This algorithm includes a preshaping profiler formulated from sampling function (also known as sinc function), consequently feedforward control inputs generated from the preshaping profiler have no frequency response above a certain designed frequency. Therefore residual vibration at the end-point of maneuver can be highly reduced with minimum loss of maneuver agility. Feedforward control inputs generated from this preshaping profiler have a continuous waveform, so this algorithm is suitable for use of linear actuators as control actuators. Flexible spacecraft dynamics model of VSOP2 including 2-CMGs and 4-RWs is used to evaluate the proposed algorithm. Copyright © 2006 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.