[P-PS06] [EJ] あかつき金星周回1.5年とその科学成果

[PPS06-P13] Initial results of Akatsuki radio occultation observations

*今村 剛¹、安藤 紘基²、野口 克行³、Häusler Bernd⁴、Pätzold Martin⁵、Tellmann Silvia⁵ (1.東京大学大学院　新領域創成科学研究科、2.京都産業大学　理学部、3.奈良女子大学　理学部、4.Universität der Bundeswehr München、5.Universität zu Köln)

キーワード：Venus, atmosphere, radio occultation

Radio science (RS) experiment in Akatsuki mission aims to determine the vertical structure of the atmosphere with radio occultation technique. The quantities to be retrieved are the vertical profiles of the temperature, H2SO4 vapor density, and electron density. Advantages of Akatsuki RS over previous missions are close coordination with onboard cameras and a rather dense sampling of the low latitude thanks to the equatorial orbit. An ultra-stable oscillator provides a stable reference frequency (Allan deviation < 1E-12 for 1-1000 s). Up to now (Jan 2017) eight occultations of the Venus atmosphere (15 profiles) have been observed from March to July in 2016. Mostly low to middle latitudes were observed in the first occultation season. Findings obtained so far include the local time dependence of the thermal structure in the cloud layer, small-scale disturbances near the cloud top, and a possible long-term change of the temperature below the cloud. Derivation of H2SO4 vapor density and electron density are ongoing. The structure of the solar corona and its variation were also explored by radio occultation technique during solar conjunction in June 2016.