Long-Life Orbital Operation Of Stirling Cycle Mechanical Refrigerators

Four Stirling Cycle mechanical refrigerators are presently providing orbital cooling of two gamma-ray spectrometer instruments.' Each instrument uses two refrigerators that can be operated together or separately. The units have been operating since February 1979 without failure. Performance has degraded due to the gradual leakage of the helium working gas, necessitating operation of two refrigerators simultaneously on one instrument to attain the desired temperatures. The two-stage refrigerators provide 0.3 W at 80 K and 1.5 W at 135 K and have demonstrated the longest duration orbital operation of any mechanical refrigerators to date. A summary of the design, ground tests, and orbital operation is presented for the cryogenic system. Apassive thermal switch was developed during the program, and its operation and performance is summarized. Orbital data that includes working gas pressure, temperatures, and heat rates are presented and compared with ground test data.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.