<title>High-stability adjustable cryogenic-compatible beam-splitter mounts for the Composite Infrared Spectrometer (CIRS) for the Cassini mission to Saturn</title>

Abstract

The composite infrared spectrometer (CIRS) of the CAssini mission to Saturn has two interferometers covering the far- IR (FIR) and mid-IR (MIR) wavelength region. The FIR is a polarizing interferometer utilizing dihedral retroreflectors and a polarizing beamsplitter. As such, it is sensitive to extremely small alignment change of the dihedrals and beamsplitter elements. The alignment stability required of the beamsplitter through all cryogenic cycling, handling, test, and launch-induced disturbances is better than 10 arc seconds. The mount is also required to induce minimal distortion to the 1.5-micron-thick mylar polarizing element ont he FIR channel and the potassium bromide beamsplitter/compensator elements on the MIR channel. It is also required to provide biaxial tilt adjustment at the arc second level and translation adjustment of the beamsplitter elements to the few micron level, and must be locked without changing the alignment of the element. This may be the first mount to have achieved these requirements on a cryogenic instrument.