A critical overview on spacecraft charging mitigation methods

Interactions between hazardous space plasmas and spacecraft surfaces often result in spacecraft charging. Spacecraft charging may disturb the scientific measurements onboard, affect communications, control, and operations of spacecraft, and may be harmful to the health of the electronics on the spacecraft. Several mitigation methods have been proposed or tested in recent years. This paper presents a critical overview on all of the mitigation methods known to date: 1) passive methods using sharp spikes and high secondary emission coefficient surface materials and 2) active methods using controlled emissions of electrons, ions, plasmas, neutral gas, and polar molecules. Paradoxically, emission of low-energy positive ions from a highly negatively charged spacecraft can reduce the charging level, because the ions tend to return and may generate secondary electrons which then escape. We discuss the advantages and disadvantages of each of the methods and illustrate the ideas by means of examples of results obtained on SCATHA and DSCS satellites. Finally, mitigation of deep dielectric charging is briefly discussed.