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

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 are 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 in the 2050s.

Here, we report preliminary results from observing 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 (Hokkaido University Observatory and Kyoto Sangyo University Observatory) 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.