橋本 樹明

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.

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.

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.

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.