AIRS Cryocooler System Design and Development

JPL’s Atmospheric Infrared Sounder (AIRS) instrument is based on a cryogenically cooled infrared spectrometer that uses a pair of pulse tube cryocoolers operating at 55 K to cool the HgCdTe focal plane to 58 K; the instrument also includes cryoradiators at 150 K and 190 K to cool the overall optical bench to 150 K. The cryocooler system design is a key part of the instrument development and focuses heavily on integrating the cryocoolers so as to maximize the performance of the overall instrument. The cryocooler system development activity is a highly collaborative effort involving development contracts with industry and extensive cryocooler characterization testing at JPL. In the first phases of the effort, the overall cryocooler integration approach was developed by Lockheed Martin, and TRW was selected to develop and produce the flight coolers. The selected state-ofthe-art pulse tube cooler has excellent thermal performance, and has a number of attributes— particularly light weight—that greatly improve instrument integration. This paper describes the AIRS instrument overall cryogenic system design and the results achieved to date with respect to integration of the TRW pulse tube cryocoolers into this demanding instrument. Results are presented detailing the cryogenic loads on the cooler, the overall cryocooler thermal performance margins achieved, and thermal heatsinking considerations. Mass properties of the cryocooler system, and thermal properties of the developed cold link assembly are also presented.