Environment Exposure Tests of Electron-Emitting Film for Spacecraft Charging Mitigation

A new electron-emitting device operating in completely passive manner has been developed to prevent spacecraft charging and discharging. It is named as electron-emitting film (ELF) for spacecraft charging mitigation. This emitter (ELF) utilizes the field enhancement at the triple junction formed at the interface where metal and insulator are met and exposed to vacuum. ELF emits prebreakdown emission current that might lead to arcing at the triple junction. Hence, it balances the input and output currents to the spacecraft during substorm. After ensuring the robustness of this ELF against ground handling and in-orbit contamination, laboratory experiment confirmed continuous electron emission for 100 accumulated hours to assure the endurance. In this paper, its durability against high-energy electron and proton irradiation equivalent to ten solar years in GEO is reported. Effect of heat cycling (-150 degrees C-100 degrees C) and vacuum ultraviolet irradiation in GEO on this emitter is also completed. Postemissions of this ELF confirm the durability under those harsh space environments.