矢野 創

<p> Cosmic dust measurement has been one of the fundamental investigations of the Solar System exploration and sample returns from low Earth orbit have substituted knowledge gaps of the terrestrial collection of astromaterials. Exo-planetary system studies now demand deeper understanding of the Solar System dust structure and compositions as templates for all other planetary systems in the Universe. Sample return technologies and operations have been extended to asteroids and comets, cosmic dust parent bodies, and advanced toward more challenging destinations such as Jupiter Trojans and icy satellite plumes. These achievements inevitably created the new research field of microgravity geology. After a quarter century of scientific and engineering advancements, Japan now has original dust detectors, collectors, and sample return instruments supported by ground hypervelocity impact and microgravity experimental facilities. </p>

地球生命の誕生に，地球外有機物が重要な役割を果たした可能性が議論されている。特に宇宙塵（惑星間塵）は有機物の運び手として重要であると考えられる。たんぽぽ計画は，国際宇宙ステーション曝露部でエアロゲルを用いて高速で飛来する宇宙塵等を捕集し，分析することや，宇宙塵中の有機物の宇宙での安定性を評価するためにアミノ酸関連分子の宇宙曝露を行うこと等を含む日本初のアストロバイオロジー実験であり，2015年5月に実験が開始された。本講演では，その現状と，2016年以降に予定されている帰還後の分析準備について報告する。

木星のラグランジュ点付近に存在するトロヤ群小惑星の起源は、よくわかっていない。我々は（１）種々の氷・含水鉱物・有機物が特徴的な吸収を持つ赤外域（とくに2500$\sim$5000 nmの波長域）でトロヤ群小惑星のイメージング分光を行う母機（２）小惑星表面に降り立ち揮発性の高い炭素・水素・窒素・酸素などの同位体比をその場測定する子機、から成るソーラー電力セイル探査機の検討をすすめている。2020年代に打ち上げるために進行中の、ミッション設計・探査候補天体のサーベイ・搭載機器開発について報告する。

© 2016 International Astronomical Union. Commission 15 of the International Astronomical Union (IAU), entitled Physical Study of Comets and Minor Planets, was founded in 1935 and dissolved in 2015, following the reorganization of IAU. In 80 years of Commission 15, tremendous progress has been made on the knowledge of these objets, thanks to the combined efforts of ground- A nd space-based observations, space mission rendezvous and flybys, laboratory simulation and analyses of returned samples, and theoretical and numerical modeling. Together with dynamical studies of the Solar System, this discipline has provided a much deeper understanding of how the Solar System formed and evolved. We present a legacy report of Commission 15, which highlights key milestones in the exploration and knowledge of the small bodies of the Solar System.

JAXA is planning to launch Hayabusa 2 in December 2014. Hayabusa 2 will be equipped with an asteroid exploration rover which is developed by the consortium of universities. A goal of the rover is establishment of the technology for locomotion on asteroid surface. In our previous work, we proposed a new moving mechanism called "Environment-Driven Torquer, EDT." The EDT is driven by environment temperature with bimetal. In other words, the EDT can move the rover without both battery and CPU. We have developed an engineering model with magnet latch. In this paper, performance evaluation of the EDT is executed by free-fall experiments in ZARM.

Asteroid probe Hayabusa 2 is developed by JAXA. Asteroid exploration rovers will be carried by Hayabusa 2. In our research project, we have developed an environmental-temperature-driven buckling actuator with a bimetal thin plate for a hopping mechanism of the rover. In this study, to characterize the hopping capability of the actuator, we conducted microgravity examination in ZARM drop tower. We fabricate a test rover for the microgravity examination with a rapid heating system for actuation in short free-fall time. Although reaction force from baseplate was incomplete in take-off, the rover hopped with a vertical velocity of 3.12 mm/s with 0.035 rad/s rotating rate.

Copyright © 2014 by the International Astronautical Federation. All rights reserved. The micron sized debris cannot be detected by the ground-based observation network. It is necessary to predict their spatial and temporal distribution using a dynamic flux model. This study is part of a "Tanpopo" mission, which plans to capture micron-sized debris, micrometeoroids, and organic substances, and expose terrestrial microbes at the Japanese "Kibo" module of the International Space Station. The purpose of this study is to directly estimate the diameter and impact energy of impacting particles based on the craters found in the capture panel which is used for exposed experiment of the Tanpopo mission. Hypervelocity impact experiments were conducted with the two-stage light gas gun using the same aluminum-alloy plates as used for the mission capture panel. Projectiles consisting of aluminum, aluminum oxide, and stainless steel spheres with diameters of 0.1-0.5 mm were used, and they were launched using a shotgun technique at approximately 6.5 km/s. The relationships between the crater diameter and impact conditions based on the crater shapes were investigated. It was found that the particle diameter and impact energy could be calculated using the crater diameter and crater depth, with no data on the impact particle material. By assuming that the calculated crater volume was half the volume of the spheroid and directly measuring the crater volume using a 3D laser microscope, the impact energy could easily be predicted by measuring the crater diameter and crater depth. Furthermore, numeral simulations were conducted with the hydrocode "Autodyn", and the results of it were compared with that of the impact experiments. The crater diameters were included in the error range. However, the crater depths were lager than measurement value.

The Memorandum of Understanding signed between the Japanese Aerospace Exploration Agency (JAXA) and the German Aerospace Centre (DLR) during the 63rd International Astronautical Congress (IAC) in Naples, paves the way for the Mobile Asteroid Surface Scout (MASCOT) participation in JAXAs Hayabusa-II mission. Like its famous predecessor, Hayabusa-II is foreseen to study and return samples from a Near-Earth Asteroid. In contrast to the previous mission, Hayabusa-II will also include a small lander package being developed by DLR and the Centre National d'Etudes Spatiales (CNES): the aforementioned MASCOT. Scheduled for a launch in 2014, Hayabusas-II journey will take 4 years until it will arrive at 1999JU3, a C-type asteroid. Following the initial remote sensing operations, MASCOT will be released to the surface and perform its science operations at its first location. Once this is complete, MASCOT will be able to 'hop' from one measurement site to the next. The payload suite will comprise a near-infrared microscope (MicrOmega, IAS Paris), a camera (CAM, DLR Berlin), a radiometer (MARA, DLR Berlin) and a magnetometer (MAG, TU Braunschweig). Realizing MASCOTs mission is difficult due to the strict mission requirements, the harsh landing environment and a short development time for a piggyback deep space mission. Aiming for high performance and reliability requires creative design solutions and novel developments in order to meet all challenges and to stay inside the mass limit of 11 kg. The status of MASCOT up to end of Phase B was presented at the 63rd IAC. With a flight model delivery scheduled for March 2014, the mission is now in the final stage of development and testing. The results of these tests have shown the strict limits of the structure and thermal design, and highlighted the risk in such a short project development. Lessons have also been learned regarding margin policy for such small spacecraft. Despite these challenges, the project is on-track, with all delivery milestones expected to be met. These last few months will serve to verify all of the design assumptions, before the launch in late 2014.

The JAXA Hayabusa-II mission is the follow-up to the original Hayabusa mission launched in 2003 \ which succeeded in returning the first dust particles from a near-Earth asteroid to Earth. JAXA intends to launch Hayabusa-II in 2014 for similar measurements of the asteroid 1999 JU3, a C-type asteroid, and invited the German Aerospace Centre (DLR) to contribute a small lander package to the mission. Based on this invitation, DLR is developing the Mobile Asteroid Surface Scout (MASCOT) to complement the main spacecraft's scientific objectives, with the Centre National d'Etudes Spatiales (CNES) providing payload and subsystem support. MASCOT will provide in-situ surface science and allow investigation of up to three sites on the asteroid surface. A short on-asteroid lifetime of two complete asteroid rotations (-16 hours) will provide measurements under different illuminations and thermal conditions, with Hayabusa-II being used to transmit all of the scientific data back to Earth. The harsh landing environment and strict mission requirements lead to some difficult design challenges. An innovative "hopping" mechanism will allow MASCOT to leap across the asteroid surface in bounds of up to 220m, albeit robustness of this concept must first be proven in a comprehensive suite of simulations and tests. Mass, limited to 10 kg, is critical: savings via the use of a carbon-fibre main structure and simplified subsystems allows the carriage of four scientific payloads, namely a multispectral wide angle camera, a radiometer, a magnetometer and an IR microscope. Thermal control is a challenge given the contrasting requirements of deep-space cruise and on- surface operation. Available energy also puts a strict limit on operations and restricts the lifetime of the mission. Copyright © (2012) by the International Astronautical Federation.

Japan Aerospace Exploration Agency (JAXA) plans to launch the small asteroid explorer "HAYABUSA2" in 2014, following the HAYABUSA mission. By improving the HAYABUSA probe, we are planning to visit the small asteroid "1999JU3", and aiming sample-return from an asteroid of different type from Itokawa. The 1999JU3 is a C- Type asteroid, considered to contain more organic or hydrated materials than S-type asteroids like ITOKAWA. The basic configuration of the spacecraft is mainly the same as HAYABUSA, with several minor modifications. The spectroscopic equipment and sampling system will be improved to be more suitable to C-type asteroids, because the surface of C-type asteroids is expected to differ from that of S-type ones. We will report the details of the sampling system of HAYABUSA2, and introduce our developing status of the sampling system. Copyright © (2012) by the International Astronautical Federation.