Time-Resolved Spectroscopy of Electrostatic Discharge and Secondary Arc Plasma on Spacecraft Solar Array

Primary electrostatic discharges (ESD) and secondary arcs on spacecraft solar panels are simulated experimentally by introducing a needle trigger and investigated with a time-resolved emission spectroscopy method. The total spectral domain investigated ranges from 220 to 750 nm. An innovative active method has been developed in order to initiate ESD at a controllable time and location on triple-junction solar cells. It permits one to detect important steps of the discharge evolution, in particular the transition between primary ESDs and secondary arcs. In this experimental setup, the discharge begins on the triple-junction solar cell absorber, with gallium and germanium being detected from the very beginning. That indicates that the obtained ESDs are triggered on the solar cell edge close to the cover glass. The transition between primary ESDs and secondary arcs is accompanied by molecular material vaporization. It is thought that the glue or the underlying polyimide is evaporated mainly during secondary arcs, sometimes during primary ESDs. Once the secondary arcing is triggered, the complete edge of the solar cell assembly is impacted. That confirms that ESDs may significantly damage the solar cell assemblies.