Differential Charging of Satellite Surface Materials

High electrostatic potentials of satellite surfaces can result in electrostatic discharges (ESDs) that can damage or interfere with the satellite electronics. Measurements of the satellite conducting frame potential relative to the plasma environment are typically used to provide information on the statistical probability of charging. The frame potential is usually measured from the spectrum of the ions incident to the satellite or by voltage probes outside the satellite plasma sheath. However, ESD events are more directly related to the differential charging of various surface materials on the satellite. We will present satellite differential charging observations of several sample materials from the Satellite Surface Potential Monitor (SSPM) on the Spacecraft Charging at High Altitudes (SCATHA) mission. The SSPM data are compared statistically with measurements of the satellite frame potential and with the ESD events detected by the SCATHA discharge monitor. Local time and radial occurrence of frame and SSPM sample potentials are shown to be very similar. However, the functional relationship between the sample and frame potentials appears to differ widely from event to event.