Spacecraft charging during ion beam emissions in sunlight

Abstract : During ion beam emissions from the SCATHA satellite, the potential of the negatively charged satellite body shows a sinusoidal oscillation frequency of once per spin of the satellite. The minimum occurs when the ion beam is sunward. We consider processes that may be responsible for the voltage modulation. Neutralization of ion beam space charge by photoelectrons is examined. The photoelectrons are accelerated by the negative potential of the satellite. Effects of electron impact ionization, excitation of metastable states, and photoionization of xenon neutral atoms in the ion beam are studied in details. Critical ionization velocity interaction is unlikely under the condition considered. Keywords: Spacecraft charging; Ion beam; Differential charging; Potential barrier; Ionization; Reprints.