Effects of Evolving Surface Contamination on SpacecraftCharging
The effects of evolving surface contamination on spacecraft charging have been investigated through (i) ground-based measurements of the change in electron emission properties of a conducting surface undergoing contamination and (ii) modeling of the charging of such surfaces using the NASCAP code. Specifically, we studied a Au surface as adsorbed species were removed and a very thin disordered carbon film was deposited as a result of exposure to an intense, normal incidence electron beam. As a result of this contamination, we found an ~50% decrease in secondary electron yield and an ~20% reduction in backscattered yield. The type and rates of contamination observed are similar to those encountered by operational spacecraft. Charging potentials of an isolated panel of the material were determined under both sunlit and eclipse conditions in geosynchronous orbits for typical and extreme environments. In all environments studied, just monolayers of contamination lead to predictions of an abrupt threshold effect for spacecraft charging; panels that charged to small positive values when uncontaminated developed kilovolt negative potentials. The relative effect of NASCAP parameters for modeling secondary and backscattered electron emission and plasma electron distributions were also investigated. We conclude that surface contamination must be considered to avoid the serious detrimental effects associated with severe spacecraft charging.
W.Y. Chang, JR Dennison, Jason Kite and R.E. Davies, “Effects of Evolving Surface Contamination on Spacecraft Charging,” Paper AIAA-2000-0868, Proceedings of the 38th American Institute of Aeronautics and Astronomics Meeting on Aerospace Sciences, (Reno, NV, 2000). Paper received Certificate of Merit by the AIAA Plasmadynamics and Lasers Technical Committee for Best Paper of 2000.