AIRS

Cryocooler Assembly

Low vibration, long life focal plane operation near 58 K is critical to the success of AIRS, and the rapid advance of pulse tube cryocoolers has proven to be a key enabling technology in this area. The AIRS focal plane cryocooler, developed under contract with TRW (now NGST), is a fully redundant pulse tube refrigerator with each redundant assembly consisting of an actively balanced compressor, separate pulse tube coldhead, and independent control electronics.

The pulse tube cryocooler is a variation of the Stirling cycle refrigerator, where the moving displacer in the traditional coldhead assembly is replaced by a passive combination orifice and gas reservoir to bring about the proper phase relationship between pressure and mass flow rates. The result is an accessible cold spot for FPA cooling without the penalties of coldhead vibration, electromagnetic interference, and displacer reliability inherent in the standard approach. AIRS was the first NASA instrument to use pulse tube coolers.