講演情報
[PCG10-P03]Geophysical experiments on Phobos proposed for JAXA Mars Moon Exploration mission
*小川 和律1、田中 智2、坂谷 尚哉2、上野 宗孝1,2、星野 健2、坂本 和敏2、川村 太一3、石原 吉明2、竹内 希4、Philippe Lognonné3、新谷 昌人4、山田 竜平5、辻 健6、小林 泰三7、白井 慶8、Matthias Grott9、Jerzy Grygorczuk10、Axel Hagermann11、Jörg Knollenberg9、Tilman Spohn9、宮本 英昭4、桂木 洋光12、城野 信一12、諸田 智克12、荒川 政彦1 (1.神戸大学、2.宇宙航空研究開発機構、3.パリ地球物理研究所、4.東京大学、5.国立天文台、6.九州大学、7.福井大学、8.総合研究大学院大学、9.ドイツ航空宇宙センター、10.ポーランド科学アカデミー、11.オープン大学、12.名古屋大学)
キーワード：
MMX、Martian moon、Phobos、Planetary exploration、Internal structure
Scientific instruments and their support devices are being proposed for geophysical experiments on Phobos as potential instruments for the Mars Moon Exploration mission (MMX). JAXA is currently planning a sample return mission to the martian moons. The spacecraft will stay in a quasi-orbit around Phobos for months or 1-2 years, and make scientific observations including remote sensing, landings on Phobos for sampling, and several flybys of Deimos. Scientific goals of MMX were defined as in the following two categories: (1) To reveal the origin of the Mars moons, and then to make a progress in our understanding of planetary system formation and of primordial material transport around the border between the inner- and the outer-part of the early solar system. (2) To observe processes that have impact on the evolution of the Mars system from the new vantage point and to advance our understanding of Mars surface environment transition. While a landing site for sampling is still under consideration, in a current plan the main spacecraft lands twice, on the “red” and “blue” areas on Phobos for example.
We proposed five scientific instruments for this mission. SEIS: a three-axes short-period seismometer and an active seismic vibration source, SSXT: a penetration probe of several tens cm length with temperature and thermal conductivity sensors, miniRAD: a miniaturized thermal infrared radiometer, a muon detector, and SUMIRE: a mechanical insertion resistance probe of 5 cm length. All these instruments basically aim at investigating the geophysical properties of the surface, sub-surface, and interior of Phobos, and their combined observations can provide integrated models of mechanical and thermal properties of the subsurface which has not been studied so far. The scientific objectives of these instruments are connected to the following mission objectives corresponding to the mission goals above: (a) To obtain indirect information on the Phobos internal structure in order to constrain the origin of Phobos independent of the sample analysis results. (b) To characterize the space environment and the surface features of Phobos, with the intention of comparison with asteroids.
Because the first four of the above scientific instruments require a long observation time at a fixed location, a long-lived landing package (MSM) is also proposed. SUMIRE is planned to be mounted on the feet of the mothership (main lander). Objectives of MSM are providing electric power, command/telemetry interfaces, and an operable environment for the scientific instruments throughout a period of our observations over a Mars year. MSM has the following specifications and functions: (i) Operates independently from the mothership and survives at a fixed point of area. (ii) Controls internal temperature in an operable range of the scientific instruments for their continuous observations. (iii) Provides wired interfaces of telemetry/command and power to the scientific instruments. (iv) Communicates over a radio link with the mothership in orbits and with ground-based stations on the Earth. MSM will be placed on Phobos’ surface during the landing sequence of the main spacecraft, and stay there over its entire lifetime.
We proposed five scientific instruments for this mission. SEIS: a three-axes short-period seismometer and an active seismic vibration source, SSXT: a penetration probe of several tens cm length with temperature and thermal conductivity sensors, miniRAD: a miniaturized thermal infrared radiometer, a muon detector, and SUMIRE: a mechanical insertion resistance probe of 5 cm length. All these instruments basically aim at investigating the geophysical properties of the surface, sub-surface, and interior of Phobos, and their combined observations can provide integrated models of mechanical and thermal properties of the subsurface which has not been studied so far. The scientific objectives of these instruments are connected to the following mission objectives corresponding to the mission goals above: (a) To obtain indirect information on the Phobos internal structure in order to constrain the origin of Phobos independent of the sample analysis results. (b) To characterize the space environment and the surface features of Phobos, with the intention of comparison with asteroids.
Because the first four of the above scientific instruments require a long observation time at a fixed location, a long-lived landing package (MSM) is also proposed. SUMIRE is planned to be mounted on the feet of the mothership (main lander). Objectives of MSM are providing electric power, command/telemetry interfaces, and an operable environment for the scientific instruments throughout a period of our observations over a Mars year. MSM has the following specifications and functions: (i) Operates independently from the mothership and survives at a fixed point of area. (ii) Controls internal temperature in an operable range of the scientific instruments for their continuous observations. (iii) Provides wired interfaces of telemetry/command and power to the scientific instruments. (iv) Communicates over a radio link with the mothership in orbits and with ground-based stations on the Earth. MSM will be placed on Phobos’ surface during the landing sequence of the main spacecraft, and stay there over its entire lifetime.