川口 淳一郎

The cathode-less electron cyclotron resonance ion engines, μ10, propelled the Hayabusa asteroid explorer, launched in May 2003, which is focused on demonstrating the technology necessary for a sample return from an asteroid, using electric propulsion, optical navigation, material sampling in a zero gravity field, and direct re-entry from a heliocentric orbit. It rendezvoused with the asteroid Itokawa after a two-year deep space flight using the ion engines. Though it succeeded in landing on the asteroid on November 2005, the spacecraft was seriously damaged. This delayed Earth return in 2010 from the original plan in 2007. Reconstruction on the operational scheme using thrust vector control of ion engines, Xe cold gas jets and solar pressure torque made Hayabusa leave for Earth in April 2007. Although most of the neutralizers were degraded and unable to be used in fall of 2009, a combination of an ion source and its neighboring neutralizer has kept the orbit maneuver to Earth including a series of final trajectory correction maneuvers. Finally, the spacecraft decayed in atmosphere and only the reentry capsule was retrieved from the Australian outback on June 14th, 2010. For the round trip space odyssey between Earth and the asteroid, the ion engines served the total accumulated operational time 39,637 hour·unit, the powered spaceflight in 25,590 hours, delta-V of 2.2 km/s, total impulse of 1 MN·s and 47 kg Xenon propellant consumption. © 2011 IEEE.

太陽系形成期の研究は，主に隕石を参照することにより検証がおこなわれ，進展して来た．隕石は小惑星の破片であるといわれているが，母天体となる小惑星が確認されている隕石は一つもない．小惑星イトカワにタッチダウンした惑星探査機はやぶさが，昨年，小惑星イトカワの表面物質を地球に持ち帰った．採取された試料は，最大で数百ミクロンの微粒子であるが，これらの試料を分析することにより，小惑星と隕石との関係の一部が初めて明らかになっていくことが期待される． 本講演では，酸素同位体組成，マグネシウム同位体組成戸26Al，微量元素組成について報告する．

Japan Aerospace Exploration Agency (JAXA) successfully achieved the world's first solar power sail technology by IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) mission in 2010. It demonstrated a photon propulsion and thin film solar power generation during its interplanetary cruise. The 200m2-span sail was deployed and kept extended by centrifugal force of the spacecraft rotation. IKAROS also succeeded in accelerating and controlling the orbit by actively exploiting solar radiation pressure, and thus became the world's first actual solar sailer flying an interplanetary voyage. This paper presents the design of IKAROS solar sail system, operation results and introduces a perspective of this new technology to apply to the next generation mission toward Jupiter and Trojan asteroids.

Hayabusa spacecraft finally came back to the earth on June 13, 2010. It has a quite dramatic story and we had a lot of experiences about planetary mission. And now we have proposed Hayabusa follow-on mission, Hayabusa-2. It is an asteroid sample return mission again, but the type of the target asteroid is C-type, which is different from the target of Hayabusa, Itokawa (S-type). The scale of the spacecraft is similar to Hayabusa, but many parts will be modified so that we will not have the troubles that we experienced in Hayabusa. Also the spacecraft has new equipment, which is called impactor. The impactor will make an artificial crater on the surface of the asteroid, and we will try to get the sample inside the crater. Then we can get much fresh material. The planned launch year is 2014 or 2015, arriving at the target asteroid 1999 JU3 in 2018, and coming back to the earth 2020. We hope we can start this mission as soon as possible. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

2003年5月に打ち上げられ、2005年9月に小惑星イトカワに到着、2010年6月に地球帰還を果たした小惑星探査機「はやぶさ」について、その概要、通信系構成、通信途絶後の復旧作業について述べる。

The Japan Aerospace Exploration Agency (JAXA) makes the world's first solar power sail craft IKAROS demonstration of photon propulsion and thin film solar power generation during its interplanetary cruise. The spacecraft deploys and spans a membrane of 20 meters in diameter using the spin centrifugal force. It also deploys thin film solar cells on the membrane, in order to evaluate its thermal control property and anti-radiation performance in the real operational field. The spacecraft weighs approximately 310kg, launched together with the agency's Venus Climate Orbiter, AKATSUKI on May 21, 2010. This paper presents the summary of development and operation of IKAROS.

The asteroid explorer Hayabusa, which is the spacecraft for asteroid sample return mission of Japan, came back to the Earth on June 13, 2010, seven year after the launch. It is the first spacecraft in the world that went to a solar system body farther than the moon, touched down on its surface, took off, and came back to the earth. Hayabusa has many new challenges; some of them were successful but others were unsuccessful. As the results, Hayabusa revealed the strange nature of a small near earth asteroid, Itokawa. In this paper, we describe the whole mission of Hayabusa.

ソーラーセイルWG では,太陽の光子の圧力を受けて進む光子セイルに,薄膜太陽電池を貼り付けて大電力を発生し高比推力のイオンエンジンを駆動する推進システム,ソーラー電力セイルの検討を進めている.このシステムの確立において重要な技術課題である大型膜面の展開機能を検証するため,大気球を用いた大型膜面の展開総合実験を計画し,展開システムの開発を行った.あいにく実験場の天候不良により平成20 年度に続き,放球を実施できなかったが,本論文では,この実験の内容および位置付けについて紹介する.

In this article, preliminary feasibility assessment of aeroassist systems for JAXA's future Mars Exploration has been conducted. The aerobraking technology is found to bring about an increase in the payload ratio by considerable reduction of the propellant mass required for orbital descent after propulsive orbital insertion. The aerocapture technology, if accuracy in both the interplanetary orbit determination and guidance is improved, is shown to achieve a remarkable increase of the payload mass using the state-of-the-art technologies. Discussions are made on the guided entry systems which are expected to realize better landing mark precision than obtained by the ballistic flight.

As many varieties of microsatellite missions have been purposed, microsatellite's performances are becoming higher level. It is important to develop higher level 3-axis attitude control mechanics. We purpose an innovative 3-axis attitude control for microsatellite by using Reflectivity Control Device, RCD which is capable of changing its reflectance by imposed voltage. This paper shows one example of 3-axis attitude control using RCD, and advantages of this method by being compared to non RCD methods which used only reaction wheel.