Outgassing from spacecraft materials contaminates the spacecraft's thermal control systems and optics. Solar ultraviolet light induces darkening of the organic molecular contaminants that accumulate on the surfaces. These contaminants include hydrocarbon, phthalate, amine and siloxane. To better understand the characteristics for the darkening of the organic molecular contaminants, we studied the optical degradation of the contaminants under ultraviolet (UV) irradiation and vacuum conditions.

more »

... ualene, tetra-methyl tetra-phenyl tri-siloxane, polydimethylsiloxane, oleamide and diethylhexyl phthalate were used as contaminants. In our study, near UV irradiation induced decreases in the transmittance for all chemical compounds. The transmittance in shorter wavelengths, after UV irradiation, was less than that observed in longer wavelengths for all compounds.