The effects of ultraviolet radiation in the 500A to 2,000A wavelength region on the spectral reflectance and integrated solar absorptance of three thermal control surface coatings were investigated. The coatings investigated were polished 99.99+% aluminum/ and silicone alkyd and melamine modified poly-vinyl butyral pigmented 60% by volume with titanium dioxide (TiO2). Samples of the coatings were exposed for 96 hours in 10-6 Torr vacuo to radiation from a capillary discharge of hydrogen gas. The spectral reflectance in the 4,000A to 7,000A and 20,000A to 150,000A regions was determined before and after the 96 hour exposure periods. It was found that the maximum decrease in spectral reflectance occurred between 4,200A and 4,600A and was equal to 0.10 for the silicone alkyd/Ti02, 0.07 for the melamine modified polyvinyl butyral/Ti02, and 0.06 for the polished aluminum. The integrated solar absorptance was calculated before and after the exposure periods. It was found that the integrated solar absorptance changed from 0.196 to 0.219 for the silicone alkyd/TiO2, from 0.232 to 0.248 for the melamine modified polyvinyl butyral/Ti02, and from 0.27 to 0.30 for the polished aluminum.
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