CONTAMINATION AND SPACE ENVIRONMENTAL-EFFECTS ON SOLAR-CELLS AND THERMAL CONTROL SURFACES

For surfaces in low Earth orbit on the International Space Station, co ntamination may occur from Space Shuttle thruster exhaust, sputter con tamination products, and products of silicone degradation. Interaction of the natural low-Earth-orbit environment with the surface contamina nts may degrade the performance of solar cells and thermal control coa tings. This paper describes laboratory testing in which solar-cell mat erials and thermal control surfaces were exposed to simulated space en vironmental effects including contamination, atomic oxygen, ultraviole t radiation, and thermal cycling. Contamination from thruster exhaust in amounts significantly exceeding those expected on the Space Station resulted in increased solar absorptance of surfaces and in degradatio n of solar-cell performance. Fused silica samples that were subsequent ly exposed to an environment dominated by atomic oxygen and containing some vacuum-ultraviolet radiation showed reversal of this degradation , Materials which were exposed to vacuum-ultraviolet radiation subsequ ent to thruster-exhaust contamination showed slight additional degrada tion in solar absorptance. Despite significant differences between the simulated environments and the low-Earth-orbit environment, these dat a are useful in suggesting possible trends in performance changes for solar cells and thermal control surfaces due to the interactions betwe en surface contaminants and the natural low-Earth-orbit environment.