Evaluation of Thermal Control Coatings Degradation in Simulated Geo-Space Environment

Abstract

This paper describes a study carried out to evaluate solar absorptance and infrared emissivity degradation of many different thermal control materials (white paints, second-surface mirrors and aluminized films) exposed to geostationnary orbit. For this purpose, a long-term test of about 3 months in constant vacuum was performed reproducing a 3-year space environment exposure including ultraviolet and charged particle effects on North/South panels of a geostationary three-axis stabilized spacecraft. Reflectance spectra were measured in situ in the solar range (250-2500 nm) and the corresponding solar absorptance values were calculated. The test methodology and the obtained degradations of many materials are discussed. Instead of a constant increase with irradiations, oscillations of solar absorptance were obtained for some materials depending on the test sequence. The most important degradations were found in white silicone paints whereas second surface mirrors and aluminium paints remained quite stable.