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 Terrestrial Thermal Emission Radiometer (OTTER) instrument and a multi-band Visible InfraRed Earth Observation (VIREO) camera. The purpose of the OTTER instrument is to acquire multispectral images of the Earth in the mid and thermal infrared ranging from 4 um to 12 um. These images provide the remote sensing data needed to inform key research and applications focus areas of ecosystems and natural resources, hydrology, weather, climate, and solid Earth. Launch is scheduled for 2027 with a three-year prime mission in a sun syn-chronous orbit at an altitude of 662 km. OTTER is an eight-band radiometer that expands on the heritage design of the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) instrument utilizing a telescope to focus the optical signal onto spectral filters on an actively cooled 65 K focal plane array, a double-sided scan mirror rotating at constant speed and two internal blackbody calibration targets. The OTTER thermal control architecture consists of active and passive elements and implements a heat rejection system that differs notably from that of ECOSTRESS. An overview of the overall thermal control design approach is presented along with discussion of various trade studies that have been performed.