# # Program information file # PROGRAM_ID 2022B073 PROGRAM_TITLE Studying Io's Seasonal Atmosphere: Approach to Perihelion PROGRAM_INV1 John Spencer PROGRAM_INV2 PROGRAM_INV3 PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT major planets / satellites PROGRAM_ABSTRACT_BEG We will use TEXES to measure the temporal and longitudinal variability of Io's atmosphere, using SO2 bands near 19 um. The data will extend a 21-year record of the spatial inhomogeneities and seasonal variation of the atmosphere. A sharp peak in anti-Jovian atmospheric density was seen near perihelion in 2011, providing strong evidence for sublimation support. We plan to monitor atmospheric response around the early 2023 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. We will ratio our Io spectra to Callisto spectra to remove telluric and instrumental signatures from the data. .SNR of 250 is expected given the known brightness of Io for the proposed integration times, sufficient to retrieve the SO2 column abundance to within 10%. PROGRAM_ABSTRACT_END