[P-PS01_30PO1] Toward JUICE and future explorations of outer solar system

[PPS01-P01] 木星圏探査機JUICE搭載サブミリ波放射計SWIの開発

*佐川 英夫¹、笠井 康子¹、菊池 健一¹、西堀 俊幸²、真鍋 武嗣³、落合 啓¹、黒田 剛史⁴、関根 康人⁵、Hartogh Paul⁶ (1.情報通信研究機構、2.宇宙航空開発研究機構、3.大阪府立大学、4.東北大学、5.東京大学、6.マックスプランク研究所 太陽系研究部門)

キーワード：木星, 氷衛星, JUICE, サブミリ波, リモートセンシング, 測器開発

The Submillimetre-Wave Instrument (SWI) is a passive submillimeter-wave heterodyne instrument proposed as one of the scientific payload instruments for the Jupiter Icy Moons Explorer (JUICE) mission. It measures the thermal emission from atmosphere of Jupiter and its moons at the frequency region of 500 - 600 GHz (with keeping 1200 GHz range as an optional concept). Thermal emission from the surface of moons will also be measured. JUICE/SWI provides unique observational data for characterization of the Jovian stratosphere such as thermal structure, dynamics, and distribution of minor species; and for exploration of tenuous-atmosphere and surface environment of the Jovian moons. By detecting hydrogen and oxygen isotopes in the water vapor of Jovian moons' atmosphere, SWI can also contribute to understanding the origin and distribution of water in our solar system.
This paper presents the current status of the development of SWI instrument, including the updates on the science targets and their feasibility studies. The SWI instrument is being developed through international cooperation. The Japanese team contributes to the development of the submillimeter reflector (mirror). The submillimeter reflector is one of the key components of SWI, and it determines the spatial resolution of observations. Currently a 30-cm aperture diameter reflector is considered, providing a spatial resolution of 2 mrad (FWHM) at 600 GHz. In order to fulfill the stringent requirement of weight reduction, we evaluated the material of the reflector and optimized its rib structure. The side lobe suppression is also an important factor to improve the quality of observations.