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Prevention of spacecraft charging and discharging has become increasingly important as geostationary Earthorbit satellites employ higher bus voltages. There are numerous mitigation techniques against spacecraft charging, including electron emission from the spacecraft chassis. A new electron emission device operating in a completely passive manner has been developed, which uses the field enhancement at the triple junction where the interface of metal and insulator is exposed to space. It has been named electron-emitting film for spacecraft charging mitigation (ELF'S CHARM). Microetching was applied to polyimide-copper laminated film to manufacture a laboratory prototype. This prototype ELF maintains the emission current at the steady state from the triple junctions instead of leading to arcing. The electric field at the triple junction is macroscopically enhanced by charging the polyimide film and microscopically by dielectric impurities on the copper surface. The laboratory experiments confirmed a stable current emission from 10 to 100 A for 4 hr from a 5-mm square sample having a 500-m microetching pattern. Recently, the endurance of this ELF design has been confirmed by 100 hr of accumulated emission testing. Nomenclature V = voltage difference across insulator, V CG = surface insulator (cover glass) potential, V S = spacecraft chassis potential, V

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