<title>Design and performance analysis of the wide-field infrared explorer H2/H2 cryostat</title>

The wide-field infrared explorer (WIRE) is a small explorer (SMEX) mission that will fly in the fall of 1998. The WIRE mission proposes to conduct a 4-month survey of more than 100 degree<SUP>2</SUP> of sky using 12- and 25-micrometers detectors. The instrument requires cryogenic cooling of its focal planes and telescope in order to achieve the required performance sensitivity. In addition, because of the SMEX nature of the experiment, the mass of the cryostat must be less than 60 kg. The most mass efficient system meeting the lifetime requirement was determined to be a dual stage H<SUB>2</SUB>/H<SUB>2</SUB> cryostat. The focal planes are conductively cooled by the primary H<SUB>2</SUB> while the telescope is cooled by the secondary H<SUB>2</SUB>. The secondary H<SUB>2</SUB> also protects the primary H<SUB>2</SUB> by intercepting the parasitic heat loads. This paper describes the design and performance of the H<SUB>2</SUB>/H<SUB>2</SUB> cryostat.