Perhaps the most pernicious types of spacecraft contaminants are photochemically deposited ('solarized') molecular films. The magnitudes of the effects of these films on thermal control and solar photovoltaic surfaces are difficult to predict with high reliability. This uncertainty has two primary origins. Spacecraft contaminant films are not made of pure, well characterized materials, and, once they are deposited, they can become further darkened by energetic radiation in the natural space environment. This paper presents the results of a laboratory study aimed at gaining a greater understanding of the impact photochemical deposition on spacecraft and other optics. Photodeposition results and analyses of the ultraviolet and visible transmission spectra of films from several organic precursor molecules are reported. The major differences among contaminant film types have been found to be in the initial photodeposition propensity, rather than in the ultimate optical properties of the films. Models of the effects of the photodeposits on thermal control surfaces are presented.
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