Thermal Vacuum Testing of the HVM3 Instrument and UCIS-Moon Imaging Spectrometer

Over the span of approximately one year, the High- Volatiles and Minerals Moon Mapper (HVM3) instrument for the orbiting Lunar Trailblazer (LTB) Mission and the Ultra Compact Imaging Spectrometer for the Moon (UCIS-Moon) for a future lunar surface mission underwent successful thermal vacuum testing including cold alignment, thermal balance and calibration. These two imaging spectrometers are designed to measure minerals, molecular water, water ice and OH-bearing species on the Moon. They have a spectral range of 0.6 μm to 3.6 pm with a spectral resolution of 10 nm and share the same spectrometer design but with different front optics and thermal management systems. They require temperatures of 120 K and <190 K on the detector and spectrometer, respectively. Their similarities allowed for the majority of the ground support equipment to be interchangeable. The HVM3 thermal vacuum campaign began with cold alignment of the telescope, spectrometer and focal plane in April 2022. Cold alignment was completed after two cycles and then the rest of the instrument was assembled. In October 2022, thermal vacuum testing of the entire instrument began. This test campaign included thermal balance as well as instrument calibration. Immediately after the conclusion of the HVM3 instrument level thermal vacuum test, the UCIS-Moon cold alignment testing began. After four cold alignment cycles, the UCIS-Moon telescope, spectrometer and focal plane were all aligned. The cold alignment tests were followed by calibration and thermal balance that concluded in early February 2023. This paper describes the thermal system design and numerous associated challenges and lessons learned for the various thermal vacuum tests that were performed.