Calorimetric measurements of thermal control surfaces at geosynchronous orbit

Abstract

Calorimeter data for up to 18,000 equivalent sun-hours are presented for a.number of satellite thermal control surfaces. This has been an ongoing study by Aerojet ElectroSystems. Solar absorptance values as a function of time were collected at geosynchronou s orbit on samples of zinc orthotitanate paint, silver-alumina-silica, silvered Teflon, aluminized Teflon, silica cloth, and clean second-surface mirrors. Over 6000 equivalent sunhours of calorimeter data were also collected on precontaminated second-surface mirror samples (also on-orbit). A useful collection of solar absorptance degradation equations is the result. These equations are of major significance in predicting satellite useful life. Nomenclature t - time T = temperature am - maximum solar absorptance a0 = initial solar absorptance as = solar absorptance £ = emissivity r = time constant