The space infrared telescope facility (SIRTF) cryogenic telescope assembly (CTA) cryogenic and thermal system

SIRTF is the last of NASA's great observatories. The thermal function of the CTA is critical to the success of the SIRTF mission. The CTA cryogenic and thermal system will provide the low temperature environment that the telescope and science instruments require to conduct infrared observations. A key issue with the early flight data is the peak helium bath temperature, which depends upon cryostat isolation, the helium vent path, and pre-launch cryostat operations. This paper includes a general description of the CTA thermal/cryogenic system, followed by an update on the cryostat status and a discussion of the analysis and performance testing of the porous plug and helium vent path. The pre-launch cryostat preparations have been demonstrated, and those results are presented. There is also summary of performance from the observatory thermal balance test, which completes the verification of the CTA external thermal system. All of the pieces are in place for a successful SIRTF launch and mission.