川勝 康弘

平成30年度宇宙輸送シンポジウム（2019年1月17日-18日. 宇宙航空研究開発機構宇宙科学研究所（JAXA)(ISAS)）, 相模原市, 神奈川県資料番号: SA6000136091レポート番号: STEP-2018-036

<p>JAXA has a plan to send a spacecraft to the Martian moons in the 2020s. The spacecraft needs to transfer to the orbit of one of the Martian moons. In this study, we investigate the maneuver design method and the characteristics of orbit injection that minimizes the velocity increment Δv for the JAXA's Martian exploration mission. In the previous study, a transfer trajectory with three impulsive maneuvers has been demonstrated and it has been shown that setting the initial argument of periapsis to be zero is effective to reduce the Δv for the transfer. In this paper, we proposed the optimal transfer trajectory with four impulsive maneuvers based on the grid searching of maneuver position. First, it is shown that when the declination of v-infinity vector is large relative to the Mars equatorial plane, there exists a region where adopting four impulsive maneuvers reduces the total Δv compared to the three impulsive maneuver transfer. Also, we show that optimal value of the initial argument of periapsis slightly deviates from zero when the declination is large. Finally, we investigate which transfer type has the smaller Δv for each of the possible launch windows of JAXA's Martian exploration mission.</p>

The surface of the Martian moon Phobos exhibits two distinct geologic units, known as the red and blue units. The provenance of these regions is uncertain yet crucial to understanding the origin of the Martian moon and its interaction with the space environment. Here we show that Phobos' orbital eccentricity can cause sufficient grain motion to refresh its surface, suggesting that space weathering is the likely driver of the dichotomy on the moon's surface. In particular, we predict that blue regions are made up of pristine endogenic material that can be uncovered in steep terrain subject to large variations in the tidal forcing from Mars. The predictions of our model are consistent with current spacecraft observations which show that blue units are found near these regions.

第28回アストロダイナミクスシンポジウム (2018年7月30-31日. 宇宙航空研究開発機構宇宙科学研究所), 相模原市, 神奈川県資料番号: SA6000135008レポート番号: A-8

第28回アストロダイナミクスシンポジウム (2018年7月30-31日. 宇宙航空研究開発機構宇宙科学研究所), 相模原市, 神奈川県資料番号: SA6000135006レポート番号: A-6

<p>火星衛星Phobosからのサンプルリターンに挑む火星衛星探査計画 (Martian Moons eXploration: MMX) は，現在，宇宙航空研究開発機構 (JAXA) プリプロジェクトとして，2024年の打ち上げと5年の往還期間を設定し，精力的な検討・初期開発が進められている．MMXは，サンプル分析，Deimosを加えた火星衛星の近接観測，そして火星大気および火星圏のモニタリング観測を組み合わせることにより，惑星に寄りそう衛星という切り口と視座から，太陽系における大気と水を湛えたハビタブル惑星の形成と進化の解明に迫ろうとしている．</p>

Japanese Venus Climate Orbiter/AKATSUKI was proposed in 2001 with strong support by international Venus science community and approved as an ISAS (The Institute of Space and Astronautical Science) mission soon after the proposal. The mission life we expected was more than two Earth years in Venus orbit. AKATSUKI was successfully launched at 06:58:22JST on May 21, 2010, by H-IIA F17. After the separation from H-IIA, the telemetry from AKATSUKI was normally detected by DSN Goldstone station (10:00JST) and the solar cell paddles' deployment was confirmed. After a successful cruise, the malfunction happened on the propulsion system during the Venus orbit insertion (VOI) on Dec 7, 2010. The engine shut down before the planned reduction in speed to achieve. The spacecraft did not enter the Venus orbit, but entered an orbit around the Sun with a period of 203 days. Most of the fuel still had remained, but the orbital maneuvering engine was found to be broken and unusable. However, we have found an alternate way of achieving orbit by using only the reaction control system (RSC). We had adopted the alternate way for orbital maneuver and three minor maneuvers in Nov 2011 were successfully done so that AKATSUKI would meet Venus in 2015. We are considering several scenarios for VOI using only RCS.