# # Program information file # PROGRAM_ID 2021B034 PROGRAM_TITLE The origin of recent polar brightening on Uranus PROGRAM_INV1 Patrick Fry PROGRAM_INV2 Lawrence Sromovsky PROGRAM_INV3 PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT solar system PROGRAM_ABSTRACT_BEG The north polar region of Uranus has been brightening dramatically from 2014 through 2019, a possible response to its extreme seasonal forcing. This could be due to a decrease in the upper tropospheric mixing ratio of methane [CH4] in this region or an increased scattering by what is now believed to be a cloud of hydrogen sulfide [H2S] ice. To characterize what changes are actually occurring, we propose spatially resolved SXD SpeX observations covering the 0.7-2.5 micron range over which there are key regions where CH4 absorption is competetive with hydrogen absorption and where H2S gas absorption is competetive with CH4 absorption, allowing determination of the mixing ratios of these gases relative to hydrogen, as well as the horizontal variation and temporal changes in aerosol scattering. Central meridian and offset slit positioins will provide multiple view angles and improved constraints at each latitude. SpeX guider images will allow absolute calibration and spatial navigation. PROGRAM_ABSTRACT_END