# # Program information file # PROGRAM_ID 2024B047 PROGRAM_TITLE Vertigo at Uranus: Observing Uranus's H3+ emissions with JWST to distil the planet's longitude system PROGRAM_INV1 Emma Thomas PROGRAM_INV2 Tom Stallard PROGRAM_INV3 Henrik Melin PROGRAM_INV4 Katie Knowles PROGRAM_INV5 Paola Tiranti PROGRAM_SCICAT major planets / satellites PROGRAM_ABSTRACT_BEG Uranus's unique magnetic field and rotational axis culminates in one of the least understood auroral systems in our solar system. To improve our understanding continued investigations since 1992 have searched for both aurorae to gain insight into the ionosphere-magnetosphere coupling. The northern aurora has been identified, but there is no confirmed southern aurora sighting at present and so this proposal will locate and document short term emission fluctuations at the southern aurora, to propel the discussion, with key observations, on what drives these aurorae. Here, we propose to complement previous and future JWST IR images by using IRTF/iSHELL to document the short-term variability of Uranus's ionosphere through analysis of H3+ emission lines. JWST data has and continues to produce the highest spatial resolution surveys of the Gas Giant ionospheres but lacks the flexibility to observe daily emission fluctuation due to the telescopes over subscription. Producing multiple emission morphology maps, iSHELL will strengthen the scientific return from past and present JWST investigations: identifying consistent emission structures [aurorae] and highlight fluctuations in emission structures where we know little about such as the magnetic equator. To achieve these surveys iSHELL will use the LP3 setting, which covers a majority of IR auroral emission lines. A slit of 15' in length and 4' in width is used to collect continuous object and sky calibration frames by nodding between positions. The slit will remain fixed along the planet's rotational axis with a minimum of two slit exposures each taking 35 minutes. 11 nights of 2-hour observations in August 2024 and 11 nights in January 2025 are requested to measure the dynamic morphology of Uranus's infrared emissions and hence link spatial mappings from JWST data between 2023 and 2025, rapidly improving the precision and accuracy of Uranus's rotational phase up by 50 times the current uncertainty. PROGRAM_ABSTRACT_END