On-Orbit Performance of the ECOSTRESS Pulse Tube Coolers and Instrument - Five Years in Space

Launched on SpaceX Dragon vehicle on June 29, 2018, JPL's ECOSystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) instrument has successfully completed over five years operation in space and captured a number of important lessons learned. ECOSTRESS is a cryogenic instrument developed by the Jet Propulsion Laboratory for NASA. The mission deign lifetime for the instrument was 1-year, but due to its success and important science of high value, it has been granted several extensions to continue with on-orbit operations. To date, ECOSTRESS is manifested to remain on-board the International Space Station (ISS) through fiscal year 2028. ECOSTRESS is a multispectral thermal infrared scanner with five spectral bands at 8-12.5 μm for science and a band at 1.6 μm for hot targets and cloud detection. From the ISS, ECOSTRESS provides data with 38m in-track by 69m cross-track spatial resolution and radiometric accuracy of 1 K and nominal precision of ≤ 0.3 K. The double-sided scan mirror, rotating at 25.4 rpm, allows the telescope to view a 53° wide nadir cross-track swath width of 402 km and two internal blackbody calibration targets every 1.29 seconds. Its 13.2 μm-cutoff Mercury Cadmium Telluride focal plane detector is cooled to 64 K by a pair of pulse tube cryocooolers and a third identical cryocooler cools an intermediate cold shield to 130 K. Waste heat generated by the cryocoolers and electronics is removed via cold plate heat exchangers cooled by a circulating pumped fluid loop provided by JAXA’s JEM-EF module. Soon after the cold shield and focal plane cooled to their operating temperatures, ice contamination on the focal plane and cold shield was detected. This paper provides a general overview of the cryogenic system and presents its on-orbit performance including impacts from water-ice contamination buildup and coolant fluid loop temperature changes.