Comparison of stray light mechanisms and performance in the Infrared Astronomy Satellite (IRAS) and Shuttle Infrared Telescope Facility (SIRTF) telescopes

NASA is developing two large space-based infrared astronomy telescopes, IRAS and SIRTF. Both of these systems will be functioning in the environment of a bright thermal emitting earth and sun while concurrently having baffle surfaces radiating thermal photons which combine to produce a stray radiation background. The APART program was used to analyze the stray radiation propagation paths of both the IRAS and SIRTF designs. The SIRTF design was found to be about 103 superior in its stray radiation transmission, because several design options were able to be incorporated through different mechanical and optical constraints that were different, while being generically of a similar optical design. A comparison of the APART stray radiation analyses of the two systems will be presented illustrating how the design options altered stray-light performance.