Recent improvements in optical polishing techniques have made possible optical surfaces exhibiting random
microroughness levels of less than one Angstrom rms. One such mirror, recently produced by the Photronics
Corporation and tested at TRW, exhibited a measured microroughness of 0.22 A rms but had scatter behavior
which was not commensurate with this value. The problem was discovered to be point defects in the surface
which were not detected during profilometry, and which would not have been problematic in mirrors having
microroughnesses of a few A rms. It is concluded that visual scatter inspection, at a minimum, should be used
as an in-process polishing diagnostic, in addition to profilometry.
Molecular and particulate contamination of spacecraft optical surfaces can be extremely detrimental to optical system performance degrading system throughput and increasing stray light background. Data that characterize the impact of various contaminants especially cryo- and photo-deposited molecular films on transmission reflection and scatter from optical surfaces are needed for allocation of spacecraft contamination budgets. A facility has been developed to measure the effects of molecular and particulate contaminants on optical component performance. The TRW Optical Scatter and Contamination Effects Facility (OSCEF) is capable of measuring the Bidirectional Reflectance/Transmittance Distribution Function (BRDF or BTDF) and specular reflectance/transmittance in ambient (ex-situ) as well as cryogenic vacuum (in-situ) environments. Light sources for scatter and reflectance/transmittance measurements include Argon ion HeNe Nd:YAG and CO2 lasers at wavelengths from 351 nm to 10. 6 um. Ex-situ scatter measurements can be performed on hardware to 30 cm diameter (1 meter with some reconfiguration) over nearly 4irsr1 of scatter angle space and to within 0. 3 degrees of the specularly reflected beam. In-situ measurements can be performed on 12. 5 mm diameter witness samples at temperatures from 20 K to 373 K while contaminants from representative spacecraft materials are cryo- and/or photo-deposited onto the sample surface. Contaminant layer thickness is monitored by a thermally controlled quartz crystal microbalance (TQCM) located adjacent to the witness sample. A xenon continuum lamp (1450 to 1 800 A) is available for photochemically
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