[P-PS01] Outer Solar System Exploration Today, and Tomorrow

[PPS01-14] Future ultraviolet observation for monitoring Europa and outer planetary systems

*村上 豪¹、土屋 史紀²、古賀 亮一²、吉岡 和夫³、鍵谷 将人²、木村 智樹⁴、山崎 敦¹、鈴木 雄大³、北 元¹、桑原 正輝¹、疋田 伶奈³、垰 千尋⁵、笠羽 康正²、吉川 一朗³ (1.宇宙航空研究開発機構宇宙科学研究所、2.東北大学大学院理学系研究科惑星プラズマ・大気研究センター、3.東京大学大学院新領域創生科学研究科、4.東北大学学際科学フロンティア研究所、5.情報通信研究機構)

キーワード：紫外線、エウロパ、宇宙望遠鏡

Ultraviolet observation technique is one of the most powerful tools to investigate space environments of outer planets. Japan’s space telescope Hisaki performed long-term and continuous monitoring of Io plasma torus (IPT) in UV range. The temporal variation of IPT emissions observed by Hisaki showed Jupiter’s magnetospheric dynamics and Io’s volcanic activities. However, due to the low spatial resolution (17 arc-sec) and low sensitivity (effective area of 1-3 cm²), many science topics are not covered. For example, Hisaki cannot observe Jupiter’s and Saturn’s moons themselves because they are too small. The UV spectroscope onboard Hubble Space Telescope (HST) detected signatures of Europa’s water plume. However, due to the difficulty of long-term and continuous monitoring of Europa by HST, the frequency, periodicity, and driving processes of the plume are still open questions. It is also difficult for NASA’s Europa Clipper mission and ESA’s JUICE mission which will explore Jovian system in late 2020s to perform continuous monitoring due to their capabilities with Europa flyby observations. In order to achieve such observations, we are studying a concept of future ultraviolet spectroscopy mission. The preliminary design shows a Cassegrain telescope with 0.6-1-m primary mirror which can achieve an effective area of 100-200 cm2 and spatial resolution of 0.1-0.2 arc-sec. The baseline instruments are a spectrometer for 115-230 nm range and a wide field-of-view (~9 arc-min) imager. Here we present the overview of our mission concept, science targets, preliminary design of the ultraviolet telescope and instruments, and future plans.