吉川 真

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.

In the Hayabusa-2 pre-project, science case and onboard instruments are studied to conduct in situ observation at the surface of NEO 1999JU3, with a candidate 10kg class small lander. Science requirements, strawman payloads, and operation scenario will be briefly described at the meeting.

千葉大学大学院人文社会科学研究科研究プロジェクト報告書第196集『天文・地学分野における科学体験活動の実践と評価』 山崎良雄 編

The quasi-Hilda comets (QHCs), being in unstable 3:2 Jovian mean motion resonance, are considered a major cause of temporary satellite capture (TSC) by Jupiter. Though the QHCs may be escaped Hilda asteroids, their origin and nature have not yet been studied in sufficient detail. Of particular interest are long TSCs/orbiters. Orbiters -- in which at least one full revolution about the planet is completed -- are rare astronomical events; only four have been known to occur in the last several decades. Every case has been associated with a QHC: 82P/Gehrels 3; 111P/Helin-Roman-Crockett; P/1996 R2 (Lagerkvist); and the possibly QHC-derived D/1993 F2 (Shoemaker-Levy 9, SL9). We focus on long TSC/orbiter events involving QHCs and Jupiter. Thus we survey the known QHCs, searching for further long TSCs/orbiters over the past century. First, we confirmed the long TSC/orbiter events of 82P, 111P, and 1996 R2 in order to test our method against previous work, applying a general N-body Newtonian code. We then used the same procedure to survey the remaining known QHCs and search for long TSC/orbiter events. We newly identified another long TSC/orbiter: 147P/Kushida-Muramatsu from 1949 May 14 (+97days/-106 days)--1961 July 15. Our result is verified by integrations of 243 cloned orbits which take account of the present orbital uncertainty of this comet. This is the third long TSC and the fifth orbiter to be found, thus long TSC/orbiter events involving Jupiter have occurred once per decade. Two full revolutions about Jupiter were completed and the capture duration was 12.17 (+0.29/-0.27) years; both these numbers rank 147P as third among long TSC/orbiter events, behind SL9 and 111P. This study also confirms the importance of the QHC region as a dynamical route into and out of Jovian TSC, via the Hill's sphere.

日本惑星科学会が設立されて15年,ようやく日本独自の月惑星探査が行われ,自前のデータをもつ時代となった.「はやぶさ」,「かぐや(SELENE)」,そしてそれに続く計画.今後の月惑星探査について学会コミュニティと宇宙航空研究開発機構(JAXA)との間のコミュニケーションはますます重要性をもってきた.ここに,学会講演会の場を借りてJAXAブリーフィングを開催し,JAXA側からの報告と,意見交換や議論の場を設定した.本報告および一連の記事は,まだ記憶の失われない今のうちに,その記録として報告するものである.

国際天文学連合で採決された惑星と準惑星の定義において,この2つの種別を区別するのは「その天体の軌道近くから他の天体を排除したかどうか」である.文字通りにこの定義を当てはめると,水星から海王星までの惑星は,惑星ではなくなってしまう.なぜならば,これらの天体の軌道付近には,小惑星や彗星といった太陽系小天体が多く存在するからである.ここでは,天体の軌道運動に着目して,"さすらいの天体"と"共鳴天体"というものを定義し,これらを除いて考えれば,惑星と準惑星の区別がこの定義で可能であることを示す.

宇宙航空研究開発機構(JAXA)では,小惑星や彗星のような太陽系始原天体の探査について,「はやぶさ」以降のミッションを検討してきた.それは,「はやぶさ2」と「はやぶさMk2」と呼ばれる2つのミッションである.「はやぶさ」が,イトカワというS型小惑星を探査したので,「はやぶさ2」はC型の小惑星,そして「はやぶさMk2」はD型やP型小惑星ないし個渇彗星核が探査のターゲットとなる.このようにプログラム的に探査を行うことで,効率的に太陽系や生命の起源と進化を解明することを目指すのである.特に,「はやぶさMk2」については,ヨーロッパの研究者も関心を示しており,欧州宇宙機構(ESA)のCosmic Visionプログラムに「マルコ・ポーロ」というミッション名で共同提案し,今後,本格的な検討を進めていくことになった.

資料番号: AA0063706013

探査機「はやぶさ」が小惑星イトカワにに近づくにつれ，いくつもの奇妙なことがわかってきた。まず，表面の様子が，これまで探査機が訪れた小惑星とはまったく違っていたのだ。

By Hayabusa spacecraft, for the first time, we saw the real appearance of a very small solar system body, asteroid Itokawa, which is an S-type asteroid only about 500 m in length. We had a lot of scientific results form the observation of Hayabusa. Hayabusa is now on the way to the earth and it will come back in June 2010. While working for Hayabusa, we have been considering post-Hayabusa missions, Hayabusa-2 and Hayabusa-Mk2. Hayabusa-2 is a kind of replica of Hayabusa and it will explore a C-type asteroid. Hayabusa-Mk2 is newly developed spacecraft and its target is much more primitive objects such as P or D-type asteroids or dormant comets. In this way, we are considering programmatic missions for the exploration of primitive bodies. Since there are many small bodies in the solar system, we should have such strategic approach. From 2006, Hayabusa-Mk2 is considered with the European reserchers for small bodies of the solar system. And it was proposed to Cosmic Vision of ESA with the name of 'Marco Polo.' It has passed the first selection so now we are in the assessment phase. We hope that both Hayabusa-2 and Marco Polo will be realized in the future. We also hope that we will get the clues to solve the mysteries of the birth and evolution of the solar system and the life.