Design principles for contamination abatement in scientific satellites
- Paper ID
IAF-72-15
- author
- company
Space Sciences Department, Marshall Space Flight Center, NASA
- country
U.S.A.
- year
1972
- abstract
As space experiments develop in complexity and sophistication, the problems of interference from the self-induced local environment become more severe. Extreme care in design and operational procedure is demanded to insure that the experiments measure the intended phenomena rather than extraneous self-induced environmental effects. Optical experiments, particularly those operating in the far ultraviolet, are highly susceptible to contamination from absorption and scattering; hence, the study of such interference is referred to as ‘Optical Contamination’ or, in a more general sense, ‘Contamination’. There have been a number of experiments on both manned and unmanned spacecraft that have failed or have been severely degraded because the effect of contamination were not considered. Scattered light from ice crystals or other debris has prevented astronomical observations in the sunlit portion of the orbit. Windows and other optical surfaces have become coated with contaminating films and globules which produce scattering and absorption. Since organic molecules are particularly good absorbers in the far ultraviolet, a film of only a few monolayers can destroy the usefulness of a mirror or grating. Cooled infrared detectors have become coated with layers of ice from condensing water vapor. Mass spectrometers have become swamped by water vapor and other outgassing products. High voltage power supplies have been destroyed by arc-over because the ambient pressure was not yet below the corona region when the high voltage was activated. Such difficulties are not restricted to the operation of experiments in space. Many optical surfaces have become contaminated in vacuum chambers during tests.