Effects of Cryocontaminants on Cryogenic Superpolished Mirror and Superpolished Quartz Crystal Microbalance

Effects of contaminants on optical surfaces is a concern for space- based systems. Many systems contain cryogenic optical systems that operate at temperatures where gases such as nitrogen, oxygen, carbon dioxide, and water will condense. This study presents experimental results of the effects of these gases condensed on highly polished superpolished mirror surfaces cooled, under vacuum, to temperatures as low as 15 K. Using these gases as contaminants, the bidirectional reflectance distribution function BRDF was obtained at a wavelength of 0.6328 um for various contaminant film thicknesses up to 8 um. Most of the data were obtained using the superpolished sense crystal of a previously developed quartz crystal microbalance SPQCM as the mirror surface. The SPQM allowed the mass of the actual contaminant layer to be measured directly. This program has been sponsored by Rome Laboratory and Johns Hopkins University Applied Physics Laboratory.