Design and development status of the pulse tube cryocoolers for the Atmospheric Infrared Sounder (AIRS)

The Atmospheric Infrared Sounder (AIRS) is being developed for the NASA Earth Observing System (EOS) program with a scheduled launch on the first post meridian (PM-1) platform in the year 2000. AIRS is designed to provide both new and more accurate data about the atmosphere, land and oceans for application to climate studies and weather prediction. Among the important parameters to be derived from AIRS observations are atmospheric temperature profiles with an average accuracy of 1K in I kilometer (km) layers in the troposphere and surface temperatures with an average accuracy of 0.5K. The AIRS measurement technique is based on very sensitive passive infrared remote sensing using a precisely calibrated, high spectral resolution grating spectrometer operating in the 3.7 mu m - 15.4 mu m region. The instrument utilizes a cryogenically cooled infrared spectrometer that uses a pair of pulse tube cryocoolers operating at 55K to cool the HgCdTe focal plane detectors to 58K. The instrument also has cryoradiators operating at 190K and 150K to cool the spectrometer's optical bench to 155K. The cryocooler system is a highly integrated part of the AIRS Instrument development whose design is focussed to maximize the overall performance of the instrument. This paper provides a brief description of the AIRS Instrument design and focuses on the results achieved to date on the development and integration of the pulse tube cryocoolers into this demanding instrument. In particular, the paper will describe the cooler cryogenic and the overall. thermal performance of the cryocooler. The thermal characteristics of the cooler system with the cold link coupling assembly also will be presented.