Takashi Kubota

Japan has decided to launch the second sample return mission "Hayabusa-2" to the Near Earth asteroid 1999JU3 in 2014. The predecessor spacecraft "Hayabusa" made a great success when it returned to the Earth in June 2010 with a capsule containing some particles obtained around the S-type asteroid "Itokawa." The authors installed a tiny hopping rover called "MINERVA" into Hayabusa spacecraft. The rover was deployed at the vicinity of the asteroid in 2005, but failed to make a surface exploration since the human operator on the ground made a critical failure in deploying the rover. The second spacecraft also involves a plan to have a tiny rover system which will make a surface exploration over the 1km-sized asteroid. With the past experience in developing a rover, the authors are again working to install some rover packages to Hayabusa-2. The total concept is the same but this time multiple rovers are considered. Many of the aspects of the mother spacecraft come from the heritage of the previous explorer which was build using the technologies more than ten years ago. But the rover system is a completely brand-new one, based on the lessons learned from the previous rover system. Since the target asteroid parameters are different from the previous target, the rover design has to be made from the beginning. We also face to the another technically challenging matters arisen from the point of the distance from the Sun as well as the surface cruel temperature of low-albedo body. This paper describes the system configuration of the rover system currently designed and developed for the launch in 2014.

M-V型ロケットには,慣性航法誘導装置(ING: Inertial Navigation Guidance)を第3段計器部に搭載し、第1段から第3段までの3軸姿勢制御を行う.M-3SII型ロケットまでの姿勢基準装置は,レートジャイロ(FRIG: Floated Rate Integration Gyro)という機械式ジャイロを1軸のスピンフリーテーブル(SFAP)上に配置していたが,M-V型ロケットにおいては,ファイバオプティックジャイロ(FOG: Fiber Optic Gyro)を機軸に固定するストラップダウン方式を用いて,計算機(CPU)内部で座標変換を行う方式へと大幅に変更をしている.この新しい姿勢基準装置(IMU: Inertial Measurement Unit)は,搭載加速度を用いて,機上で航法誘導演算を行う慣性航法誘導装置INGを構成しているのも,M-V型機の特徴である.FOGは,機械的な可動部分を全くもたないため,信頼性が高く,次世代のジャイロとして諸外国が開発にしのぎを削っているものである.しかしながらその反面,その実用化,特に慣性航法誘導装置に採用されるレベルのドリフト変動を実現するのは非常に困難である.M-V型ロケットで採用しているFOGは,さまざまな課題を克服して完成したものであり,画期的な装置となっている.IMU及びCPUは,第3段の計器部に配置され,この部位での角速度情報は,姿勢変動分のインクリメントとして計測される.一方,第1段の姿勢制御においては,第1段の可動ノズルの応答を加味すると,第3段位置での角速度情報を用いるよりも,第1段後部筒部位での角速度情報を用いた方が、制御系の安定余裕を確保しやすい.そのため,第1後部筒部位には,レートジャイロが搭載されている.第2段ノズル部には,第1段飛翔中の横加速度を測定し,荷重を軽減する論理を可能とすべく,計測用として加速度計が搭載されている.また,各段には通信制御部(I/O)が搭載され,各段間のデータのやりとりを行う.

In recent years, deep space exploration has a lot of attention in the world. Planetary exploration missions have been earnestly studied in Japan as well as US and Europe. As mission requirements are high-level, such advanced technology as landing or rover exploration is required. Because direct surface exploration could throw the light upon the origin and evolution of the earth-type planets. Image processing is expected to play a very important role in deep space exploration. This paper describes image processing technology in space. This paper also presents image based schemes for global mapping, autonomous landing system, and rover navigation.