Preliminary Thermal Design of the Orbiting Terrestrial Thermal Emission Radiometer (OTTER) Instrument for the Surface Biology and Geology Thermal Infrared (SBG-TIR) Study

The Surface Biology and Geology Thermal Infrared(SBG-TIR) free-flyer spacecraft is host to the Orbiting TerrestrialThermal Emission Radiometer (OTTER) instrument and amulti-band Visible InfraRed Earth Observation (VIREO) camera.The purpose of the OTTER instrument is to acquire multispectralimages of the Earth in the mid and thermal infraredranging from 3 um to 12 um. These images provide the remotesensing data needed to inform key research and applicationsfocus areas of ecosystems and natural resources, hydrology,weather, climate, and solid Earth. Launch is scheduled for 2027with a three-year prime mission in a sun synchronous orbit atan altitude of 662 km. OTTER is an eight-band radiometerwith seven bands in the 3 um to 12 um range and an additionalband at 1.65 um. It expands on the heritage design of theECOsystem Spaceborne Thermal Radiometer Experiment onSpace Station (ECOSTRESS) instrument utilizing a telescope tofocus the optical signal onto spectral filters on an actively cooled65 K focal plane array, a double-sided scan mirror rotating atconstant speed and two internal blackbody calibration targets.The OTTER thermal control architecture consists of active andpassive elements and implements a heat rejection system thatdiffers notably to that of ECOSTRESS. An overview of theoverall thermal control design approach is presented along withdiscussion of various trade studies that have been performed.