# # Program information file # PROGRAM_ID 2024A981 PROGRAM_TITLE H2O in Comet 12P PROGRAM_INV1 Erika Gibb PROGRAM_INV2 PROGRAM_INV3 PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT comets PROGRAM_ABSTRACT_BEG We would like to request 3 hours of DDT to target comet 12P. 12P is a daytime target, but also a very bright comet that has been easy to observe during daytime hours even in less-than-optimal conditions. Due to its daytime only availability, this comet can only be targeted by infrared and radio facilities, and we have a campaign that is being coordinated by Martin Cordiner (Catholic University/NASA GSFC). As part of the campaign, there are scheduled APEX observations to measure HDO. These are scheduled between May 10 and 17. We have iSHELL time assigned through the normal proposal process to observe 12P on May 6 and 17, but 12P has exhibited some short-term variability and is an object known to outburst frequently. APEX cannot measure water, so in order to better constrain the HDO/H2O ratio, we would like to request DDT, preferably on May 11 or 12 to more closely bracket the time of the APEX observations. On these dates, 12P is at airmass less than 2 between 10:00-17:15 HST (transiting at ~13:45 HST). It will be more than 30 degrees from the Sun. To measure the water production rate, we require our Lcustom setting (WL upper = 3.100 microns). We estimate that 32 minutes on source would be sufficient to provide a sensitive measure of the water production rate and rotational temperature based on results from our ongoing iSHELL campaign. In order to more closely match the APEX beam size, we would need to nod off-chip. PROGRAM_ABSTRACT_END