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

[PPS01-12] Uranus Stellar Occultation Observation Campaign Updates from the 2024-11-12 and 2025-04-08 Events

*佐柳 邦男¹、Saunders William^1,2、Blake Geoffrey³、Chanover Nancy⁴、Dahl Emma³、French Richard⁵、Guidry Joseph⁶、Levine Stephen⁷、Person Michael⁸、Souami Damya⁹、Verbiscer Anne¹⁰、Young Leslie¹¹、Irawati Puji¹²、Poshyachinda Saran¹²、Awiphan Supachai¹²、Rattanasoon Somsawat¹²、Tasuya Orarik¹²、髙木 聖子¹³、天田 耕太郎¹³、佐川 英夫¹⁴、木村 淳¹⁵、Carrion-Gonzalez Oscar⁹、Coustenis Athena⁹、Lellouch Emmanuel⁹、Rolland Lyam⁹、Sicardy Bruno⁹、Croom Mark⁴、Schmidt Luke¹⁶、Oelkers Ryan¹⁷、DePoy Darren¹⁸、Hubbard William ¹⁹、McLeod Brian²⁰、Morgenthaler Jeffrey²¹、McCarthy Donald¹⁹、Kulesa Craig¹⁹、Jackson Brian²²、Stubbers Hailey²²、Dull James²⁴、Anderson Chris²³ (1.NASA Langley Research Center、2.Analytical Mechanics Associates、3.California Institute of Technology、4.New Mexico State University / Apache Point Observatory、5.Space Science Institute、6.Boston University、7.Lowell Observatory、8.Massachusetts Institute of Technology、9.Observatoire de Paris - PSL、10.University of Virginia、11.Southwest Research Institute、12.Thailand National Observatory / National Astronomical Research Institute of Thailand、13.北海道大学、14.京都産業大学、15.大阪大学、16.Yerkes Observatory、17.University of Texas Rio Grande Valley、18.Texas A&M University、19.University of Arizona、20.Center for Astrophysics | Harvard & Smithsonian、21.Planetary Science Institute、22.Boise State University、23.College of Southern Idaho、24.College of Idaho)

キーワード：天王星、恒星食、惑星大気、環

We report updates from two multi-observatory campaigns to observe Uranus stellar occultations. Observing stellar occultation events by Uranus addresses multiple scientific objectives including (1) characterization of the middle-upper atmosphere; (2) characterization of the ring structure; (3) improvement of the planet’s ephemeris; and (4) detection of small moons and inner rings that may pose hazard during an orbit insertion maneuver by a future mission. In particular, these observations will support the preparation for NASA’s upcoming Uranus Orbiter and Probe (UOP) mission, which is the highest-priority new Flagship mission recommended by the recent US Planetary Science and Astrobiology Decadal Survey.

The objective of our international multi-observatory campaigns is to coordinate observations of upcoming stellar occultation events that may be visible from different parts of Earth and potentially from airborne/space telescopes. Uranus occults stars more frequently when the planet crosses the galactic plane, which last happened in the 1980s-90s, and allowed observations of numerous events between 1977-1996 that improved characterization of the planet’s middle/upper atmosphere, ring structure and ephemeris. Uranus will again cross the galactic plane in the early 2030s, which offers multiple opportunities to make measurements in the 2020s and 2030s that are key to preparing for the UOP mission to arrive around 2050.

Here, we report progress on analyzing the occultation events on 2024-11-12 and 2025-04-08. In particular, the 2025-04-08 event is expected to be one of the four occultations by Uranus that promise best-quality data until at least the 2050s. The 2024-11-12 event was observed by two observatories in Japan (北海道大学大学院理学研究院附属天文台 and 京都産業大学神山天文台) and another in Thailand (Thai National Observatory, National Astronomical Research Institute of Thailand). For the 2025-04-08 event, we plan to use at least 10 observatories in the western United States between Texas and Hawaii. We will conclude with an overview of future occultation events, and a call to join our observation campaigns for upcoming occultations.