橋本 樹明

The ISAS (Institute of Space and Astronautical Science) working group is currently studying the feasibility of a Venus orbiter mission [Proposal Report of feasibility study of Venus Climate Orbiter (in Japanese), ISAS working group, 2001], called PLANETC project, in which a 3 axis stabilized spacecraft will be launched in early 2008, and it will arrive at Venus in 2009. Primary purpose of the mission is to observe Venus climate so as to understand mechanism of the global circulation and three-dimensional motion of the Venus atmosphere in the lower stratum. In order to achieve the above scientific objectives, the spacecraft will carry several types of optical cameras mainly with near-infrared wavelengths. An accurate orientation for the attitude control is required in the spacecraft design. Furthermore, thermal control of the cameras is critical, because of large heat input from camera hoods and strict requirement of low temperature of detecting head. This paper describes characteristics of the PLANET-C spacecraft. And also depicted are the mission outline and the operation plan of the attitude orientation. (C) 2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

Strategy of formation flying for the X-ray Evolving Universe Spectroscopy mission (XUES) is discussed, in which an X-ray telescope of 10 m diameter and 50 m focal length will be constructed in orbit by formation flying the X-ray mirror and the focal plane X-ray detectors on two separate spacecrafts. We first studied the thrust force required to keep the detector spacecraft (DSC) in the non-Keplerian orbit. We find the direction of the thrust vector rotates twice per a single spacecraft orbital evolution along a circle parallel to the orbital plane. The absolute value of thrust needs to be varied by a factor of two or less. The maximum thrust force required is 0.47 N assuming a 600 km altitude and a 4000 kg DSC mass. The present baseline design requires no moving mechanism, instead requires a large amount of propellant because of relatively low thruster efficiency. The spacecraft is estimated to weigh about 6000 kg. We studied an alternative design in which the thruster efficiency is optimized and showed that the spacecraft mass can be reduced to 4000 kg. This, however, requires a rotation mechanism and additional constraints on the spacecraft operation.

科学衛星ミッションは宇宙研究・観測を目的にしており、宇宙科学研究所の理学・工学両グループおよび外部の共同研究者の緊密な協力の下に進められる。理学グループがその企画をし、工学グループが担当する衛星製作やロケット打上げにも深く関与していくので、典型的ボトムアップ型プロジェクトと言える。本稿では工学実験衛星(MUSES)のミッションも含めて、宇宙科学研究所で進められるミッションを例にして、歴史の概観、ミッション内容さらには研究・開発の仕方について述べる。特にミッションを支える工学技術については、個々のミッションに対応して新しく採用したものと共に、共通的なものを重点的に説明する。

宇宙探査機の天体への着陸などに際して,対象地形の認識は重要な技術となる.地形認識のための手法の一つとして陰影画像からの形状復元が考えられるが,この処理には収束演算等の大きな計算機負荷を要する.しかし,自律誘導など,用途によっては定量的な形状を必要とせず,むしろ定性的な認識結果をロバストかつ高速に必要とする場合も少なくない.そこで本論文では,認識結果を「山」や「谷」といった基本地形カテゴリーに絞ることで問題を順問題化し,収束演算を用いずにテーブル参照のみによって陰影画像から要求地形を抽出する手法を提案し,その有効性を示す.