* Paper #lo4 1 IMAS Pulse Tube Cooler Development and Testing

An Integrated Multispectral Atmospheric Sounder (IMAS) cryocooler has been developed over the past two years for providing on the order of 0.5-watt cooling at 55K in a lightweight compact configuration. The design goal for the cooler was a factor-of-three in size and mass reduction over the AIRS cooler design. In addition, the efficiency goal for the 0.5-watt at 55K cryogenic load was a compressor input power of less than 50 W/W- 50 % lower than the AIRS cooler at that cooling capacity. The developed cooler incorporates a vibrationally balanced compressor with heat spreader in the center plate; this further increases the total system effi-ciency by maintaining a temperature difference of < 5°C between the after-cooler and the heat-rejection interface. Two different coldheads have been designed for the IMAS application: an integral-linear option, and a split-coaxial option. The integral-linear option offers efficient per-formance, and a single warm mechanical/thermal interface. The split-coaxial option offers com-pactness and some cold interface system advantages. The development of the IMAS cryocooler is presented together with thermal, vibration, and EM1 performance data gathered on the com-pleted cooler both at TRW and at JPL