Thermal Design of the Mapping Imaging Spectrometer for Europa Clipper

The Mapping Imaging Spectrometer for Europa (MISE) instrument is one in a suite of nine science instruments flying onboard the Europa Clipper spacecraft enroute to Jupiter, launched on October 14, 2024. MISE is uniquely capable of determining the composition of Europa’s surface by means of infrared spectroscopy and mapping the geologic provenance of specific materials using pushbroom imaging, allowing inference of ocean chemistry. MISE will identify and map the distributions of organics, salts, acid hydrates, water ice phases, altered silicates, and radiolytic compounds at global, regional, and local scales. The distribution maps of astrobiologically relevant compounds and their geologic context can be used to assess whether Europa’s ocean is capable of supporting life. MISE will provide fundamental information on where future Europa landers could have the highest probability of detecting evidence of life. The MISE instrument can acquire science data during each flyby for about eight hours, beginning at about 4 hours before closest approach and 4 hours outbound. The nominal mission lifetime is a seven-year cruise plus two years for primary science, with about 50 flybys. MISE is a high-optical throughput pushbroom spectrometer that can provide effective observations on the flyby mission and is designed to operate within Europa’s challenging radiation environment. The instrument has a spectral range of 0.8 5 µm at 10 nm per channel. The longer wavelengths can also be used to measure thermal emissions from currently active regions and help characterize the size of water ice grains in plumes. A pulse tube cooler is used to provide active cooling to 90 K and 85 K for the spectrometer and focal plane, respectively. The telescope and pointing mirror are passively cooled. Cooler power regulation and control is provided by the Cryocooler Electronics Unit that resides in the spacecraft vault. An overview of the overall thermal control approach, with an emphasis on the expected environments definition during cruise and flyby tour operations, is presented.