Monitoring of Venus and Mars atmosphere by time varying gravity field observation

2018 Fiscal Year Final Research Report

• Project/Area Number: 15K13565
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Solid earth and planetary physics
• Research Institution: National Astronomical Observatory of Japan (2016-2018); Japan Aerospace EXploration Agency (2015)
• Principal Investigator: Yamamoto Keiko 国立天文台, RISE月惑星探査検討室, 特任研究員 (40452263)
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: 衛星重力観測 / 時間変動重力場 / 火星大気変動モニタリング

Outline of Final Research Achievements

In this study, we aimed to monitor circulation of planetary atmosphere as time-varying gravity field by satellite gravimetry. We improved the software, which was originally developed for precise estimation of the Earth-rotating satellite orbit and the earth's gravity field, so that it can be used for the orbit simulation to monitor temporal gravity field change accompanying planetary atmosphere variation. We focused on Mars atmosphere, analyzed the atmospheric circulation model for about 9 years, and extracted atmospheric surface pressure, dry ice, water ice, dust, annual, semi-annual, seasonal fluctuation components. Then these components are converted to the observed value from gravity measurement satellites. Using these data sets, we conducted simulation of the gravity field observation. Some parameters, such as measurement method, satellite's orbit and observation period, were changed and optimized in the simulation for more efficient observation.

Free Research Field

測地学

Academic Significance and Societal Importance of the Research Achievements

本研究で実施されたシミュレーションの結果に基づき、実際に惑星大気の観測が実現された場合の、その学術的な意義は次の通りである。火星をはじめとする大気を持った惑星において、大気の循環を観測し、その運動を正しく理解することは、惑星表層の熱輸送メカニズム、気象・気候メカニズムを解明する上で重要であり、本研究で検出の対象とした質量の時間変化としての大気変動は、このメカニズムに対し、定量面での規定を与えるという役割を持つ。これは従来の気象観測では直接に得ることのできない新しい観測量であり、既存の観測、大気モデルとは独立であることから、既存の惑星大気循環モデルの検証にも役立つと予想される。