Potential modulation on the SCATHA spacecraft

Abstract

A small (1-V) modulation of the spacecraft potential is observed on the SCATHA satellite through its effects on the data from four instruments: two particle detectors and two field detectors. We show that there is a strong causal link between the modulation of the potential at this 1-V level and a nonuniform distribution of the photoemissive properties of the conducting material on the surface of the satellite.

Electron beam experiments at high altitudes

“…The electrons emitted from the antenna are attracted to the highly positive satellite, instead of being reabsorbed by the antenna. The more positive satellite represents a sink for electrons emitted from the antenna [11,12]. These data therefore support the potentials inferred from the particle data, though there are ambiguities to these interpretations.…”

“…For our purposes, a more useful measurement is the 'common mode' voltage, the probe-to-satellite potential difference. Normally, this potential difference is small, varying by a few volts with spin due to probe illumination variations and a 1V spin modulation of the satellite potential caused by variations in the exposed conducting area [10,11]. During operations of the electron gun, however, the probe represents a reference point tied to the ambient plasma, and hence gives a measure of the change in the satellite potential.…”

A Simple Model of the Effect of Solar Array Orientation on SMART-1 Floating Potential

“…Therefore, the possible variation of the solar illumination pattern on the spacecraft which may be a cause of spacecraft potential variation (cf., e.g., [7] and [8]) cannot be involved here. Instead, the cause must be sought in a possible asymmetry of the ion or electron current density.…”

Spacecraft surface charging within geosynchronous orbit observed by the Van Allen Probes

“…Extreme spacecraft charging conditions on the order of −10,000 V were first recorded by geosynchronous satellites ATS 5 and ATS 6 [ DeForest , , ]. ATS 5 and ATS 6 were largely nonconducting satellites, as was the Spacecraft Charging at High Altitude (SCATHA) satellite which also observed extreme charging [ Olsen , ; Craven et al , ]. Spacecraft surface charging at geosynchronous orbit has been studied extensively, but conclusions have been varied.…”