Design of the Cryogenic System for the Safire Instrument

Abstract

One of the primary goals of the NASA Mission to Planet Earth is to improve understanding of the ozone chemistry of the atmosphere over an extended period of time. The Spectroscopy of the Atmosphere using Far Infrared Emission (SAFIRE) instrument is being developed to conduct, for the first time, global measurements of the key ozone chemistry constituents in both the mid- and far-infrared spectral regions. Such remote, long-term observations are made possible by the recent development of compact, long-life, hybrid cryogenic dewars which are necessary to cool the sensitive detectors to the 3–4 K range. The success of this hybrid concept is based on the use of long-life, Stirling cycle cryocoolers to intercept parasitic heat from the internal radiation shields of the superfluid helium dewar. Extensive system trade studies are required to optimize the mass, power, and lifetime of these space-borne cryogenic systems. The SAFIRE Cryogenic Subsystem (CSS) is described, including the thermal performance trades leading to the chosen system configuration and the important dewar/cryocooler interface issues. SAFIRE is an international program involving contributions from the United Kingdom, Italy, and France, with the United States responsible for overall instrument integration.