Cryogenic infrared radiance instrument for Shuttle (CIRRIS) telescope

A high straylight cryogenic telescope has been developed to provide spatial definition for a Fourier Transform Spectrometer. The system is all-aluminum and uses off-axis super-polished parabolas with an advanced baffle system for high straylight performance at cryogenic temperatures. The all-reflective optical system is capable of better than 0.1 milliradian resolution over a half a degree field-of-view. The brazed mechanical structure is integrated with a careful thermal design, allowing the optics to maintain liquid helium region temperatures without the use of thermal straps. The telescope has been tested for stray light, optical performance at cryogenic temperatures and against Shuttle environmental requirements. A discussion of the design analyses, test techniques and measured results is included in the paper.