Degradation of Low-Scatter Metal Mirrors by Cryodeposit Contamination
Final rept. Jan-Dec 1973
ARO INC ARNOLD AFS TN
Pagination or Media Count:
Cryogenically cooled, low-scatter mirrors are currently in use or planned for use in space applications. An experimental investigation was made to determine the effect of condensed gases on the bidirectional reflectance distribution function BRDF of metal mirrors cooled to cryogenic temperatures. Such cryodeposits may develop from control rocket plumes and component outgassing as well as atmospheric contamination. An infrared scatter instrument system was developed for in situ measurement of the test mirror BRDF at 10.6- micrometers wavelength, and a molecular beam was used to provide a well-defined gas source for condensation on the test mirror. Both single species and mixtures were investigated at mirror temperatures from 20 K to 77 K. Oxygen and carbon dioxide deposits caused some increase in scatter, but the most catastrophic failure occurred when a cryodeposit shattered or crystallized. Conditions necessary for removal of cryodeposits are also described.
- Infrared Detection and Detectors
- Solid State Physics