Modeling of FEEP Plume Effects on MICROSCOPE Spacecraft

Several aspects of plume effects of field-effect electric propulsion (FEEP) were studied. We first estimated the contamination by cesium deposit due to charge exchange of fast ions and slow neutrals and to direct neutral impingement. Levels are rather low, with local maximums of a few tens or hundreds of angstroms per year, and not much more than 1-10 Aring farther from thruster nozzles. Neutralization of the ions emitted by FEEPs was also addressed, both concerning FEEP ion space-charge compensation and spacecraft net current, i.e., the floating potential issue. With the presence of a cathode-grounded neutralizer, the spacecraft was shown to float somewhat negatively with little dependence on the ambient environment.