# # Program information file # PROGRAM_ID 2021B091 PROGRAM_TITLE Studying Io's Seasonal Atmosphere: Approach to Perihelion PROGRAM_INV1 John Spencer PROGRAM_INV2 Constantine Tsang PROGRAM_INV3 PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT solar system PROGRAM_ABSTRACT_BEG We will continue to use TEXES to measure the temporal and longitudinal variability of Io's atmosphere, using SO2 bands near 19 um. The data will extend our unique 20-year record of the spatial inhomogeneities and seasonal variation of the atmosphere. We detected a sharp peak in anti-Jovian atmospheric density near perihelion in 2011, providing strong evidence for sublimation support. We plan to monitor atmospheric response around the late 2022 perihelion to confirm and determine the repeatability of the correlation with heliocentric distance, and look for a corresponding spike on the Jupiter-facing hemisphere. We will also look for spikes due to discrete volcanic events, and establish a record of atmospheric variability to support upcoming Juno flybys of Io. We are requesting eight 3-hour observing periods during this semester to measure Io's atmospheric density at up to 8 longitudes, to improve on recent temporal and longitudinal coverage. Observing and reduction techniques will be identical to previous years, producing similarly high-quality data. We will ratio our Io spectra to Callisto spectra to remove telluric and instrumental signatures from the data. PROGRAM_ABSTRACT_END