Verification test and evaluation of vibration characteristics for ASTER cryocooler

摘要

The advanced spaceborne thermal emission and reflection radiometer (ASTER) is an instrument which was selected by NASA to fly on the EOS-AMI platform in 1998. Two cryocoolers are required to cool infrared detectors for the short-wave infrared radiometer (SWIR) and thermal infrared radiometer (TIR). V J mission lifetime of the EOS-AMI platform is expected to be 5 years, and accordingly, an operation lifetime more than 5 years is required for ASTER cryocoolers. The goals in the development of the ASTER cryocoolers are realization of a operation lifetime of over 50,000 hours and mechanical vibration forces below 0.1 N in the frequency range from 40 Hz to 135 Hz in the direction of all three axes. A split-Stirling cycle cryocooler with clearance seals and linear motors is employed for this purpose. The compressor design adopts a piston driving mechanism which has a twin-opposed piston configuration in one compression space. The mechanical vibration caused by a displacer in the expander unit is reduced by an active balancer. Cryocoolers for SWIR and TIR have cooling capacity of 1.2 W at 70 K with power consumption lower than 55 W without control electronics. Several engineering models (EM) have been fabricated and are presently undergoing performance and life tests. Results of cryocooler verification tests and effects of jitter of mechanical vibration on the ASTER instrument are described.