SIRTF cryostat requirements and development

The Space Infrared Telescope Facility (SIRTF) is the last of NASA's four gr eat observatories, scheduled for launch in 2001. At the heart of the SIRTF observatory is a 363 1, superfluid helium cryostat, designed and built by B all Aerospace & Technologies, Inc. The cryostat houses provides the direct cooling of the three scientific instruments which will observe the infrared universe. One major innovation of the SIRTF observatory is that the instru ment optics are launched warm, and cooled down on orbit to the final operat ing temperature of 5 K by radiation to space and direct vapor cooling by th e effluent helium. To accomplish this the cryostat system design includes t wo cryogenic mechanisms, and must meet stringent cold alignment requirement s, in addition to the thermal and mechanical performance requirements typic al for space flight cryostats. Currently the cryostat is completing the fab rication and assembly process, and will go into performance testing as a sy stem in the second half of 1999. We present here the design requirements, p roduction development of the SIRTF cryostat, and the predicted ground and o n-orbit performance. (C) 2000 Elsevier Science Ltd. All rights reserved.