Flight Experiment Results of Electron-Emitting Film for Spacecraft Charging Mitigation

Abstract

Spacecraft charging poses a serious threat to satellite operation. An encounter with energetic electrons causes the spacecraft potential to become highly negative. The potential difference between the spacecraft’s chassis and the surface insulator can lead to an electrostatic discharge. If the negative potential of the satellite can be raised to near 0 V by emitting electrons from the satellite chassis, spacecraft charging can be mitigated. An electron-emitting film uses the electric field concentration near a triple junction and emits electrons in a completely passive manner. This emitter was mounted onboard the high-voltage technology demonstration satellite HORYU-II, a 30 cm cubical nanosatellite weighing 7.1 kg. HORYU-II was launched to a sun-synchronous orbit of 680 km altitude in May 2012. Experiments were conducted to measure the emission current from the emitter and the surface potential of an insulator similar to the emitter. Twenty-four trials were carried out over the aurora zone, mostly above Antarctica, from July 2012 to November 2012. Of the 24 trials, electron emission was observed in three trials. The electron emission, as high as with 1 min duration, was confirmed from this emitter, along with charging of the insulator from 1000–2000 V over the aurora zone.