# # Program information file # PROGRAM_ID 2021B007 PROGRAM_TITLE HDO and SO2 thermal mapping of the atmosphere of Venus PROGRAM_INV1 Therese Encrenaz PROGRAM_INV2 Thomas Greathouse PROGRAM_INV3 Rohini Giles PROGRAM_INV4 Thomas Widemann PROGRAM_INV5 Bruno Bezard PROGRAM_SCICAT solar system PROGRAM_ABSTRACT_BEG This is the continuation of a program initiated in 2012 to study spatial and temporal variations of SO2 and H2O [through its proxy HDO] in the atmosphere of Venus over and within the clouds. Maps of SO2 and HDO have been repeatedly recorded at 7 and 19 microns to search for short-term and long-term temporal variations. Thirteen runs have taken place between January 2012 and April 2019. Data show that the disk-integrated abundance of SO2 atop the clouds has significantly changed over this time period, by a factor up to 10. The data show evidence for a long-term anticorrelation between SO2 and H2O., which has been analyzed through GCM photochemical models. In addition, our data show that SO2 plumes appear and disappear at the cloud top with a lifetime of a few hours. Our next run is planned for June 2021. We propose to continue our observing campaign for the following objectives: [1] to obtain a reliable value of the disk-integrated SO2 content over the 2021 fall; [2] to improve our statistics about the distribution of the SO2 plumes as a function of local time [which requires one measurement per day]; [3] to further constrain the lifetime and evolution of the SO2 plumes. In addition, we plan to search again for SO2 at 8.6 microns in a spectral range which probes a region located above the clouds, in order to better constrain the SO2 vertical profile within and above the clouds. As in the past, our observations will be compared with UV observations of SO2 with the Akatsuki probe. PROGRAM_ABSTRACT_END