The Effects of High-Energy Electrons on the Charging of Spacecraft Dielectrics

Results are presented of a laboratory investigation of discharges in spacecraft dielectrics using both a low-energy electron and a combined low- and high-energy electron environment. Comparison of the charging and discharge characteristics indicates that the presence of high-energy electrons in space will result in significantly different behavior from that predicted for low-energy electron simulations alone. For Kapton, fiberglass, and second-surface mirrors, the effect of the high-energy electrons is primarily to increase the conductivity, thus often limiting surface potentials to below discharge threshold values. Variation of the relative fluxes of low- and high-energy electrons can lead to discharge; however, the magnitude of the charge blowoff is significantly smaller (~1/20) than that observed upon exposure to low-energy electrons alone. Astroquartz, which for low-energy electron exposures exhibited no measurable charge blowoff, exhibited significant charge blowoff (Ip = 2 amp) upon exposure to a combined high- and low-energy electron environment.