Cryogenic Testing of Planck Sorption Cooler Test Facility.

A test facility has been upgraded in preparation for testing of two hydrogen sorption cryocoolers operating at 18/20 K. These sorption coolers are currently under development at the Jet Propulsion Laboratory (JPL) for the Planck mission sponsored by the European Space Agency (ESA). The two units share the same process and component design with different plumbing configurations required for spacecraft integration. Previous effort at JPL has led to the successful demonstration of a prototype of the sorption cooler. Each flight unit of the sorption cooler will be tested in a vacuum chamber with simulated background environment for the spacecraft. GM cryocoolers, bulk LN2, and a chiller unit are used to establish nominal temperature stages at 50, 100, and 280 K, respectively, allowing the cold end of the sorption cooler to operate at 18/20 K. This work summarizes the scope of the test facility upgrade, including design for cryogenic cooling power delivery, system thermal management, insulation schemes, and data acquisition techniques. Ground support equipment for the sorption coolers, structural features of the test chamber, and the vacuum system involved for system testing are also described in detail. [ABSTRACT FROM AUTHOR]