Space weathering of solar array coverglasses

The harsh space environment at geosynchronous orbit (GEO) induces differential charging of spacecraft surfaces due to fluxes of high energy electrons onto and through them. Thus, satellite surfaces can charge thousands of volts with respect to each other whereas entire satellites can charge tens of thousands of volts negative of their surrounding space plasma. The ensuing electric fields can cause local discharges (arcs), endangering the normal operation of the satellite. Solar cell coverglass contamination induced by the high rate of arcing is sufficient to produce the ~1.5 percent/ year power loss in excess of radiation damage on the global positioning system (GPS) satellites. This work focuses on evaluation of a GEO space weather effect, caused by 90 keV high-energy electron radiation, on material properties of different types of commonly used in space solar cell coverglasses (CMX, fused silica, and 0214). Charge analysis performed with a GPS Block IIF NASCAP model demonstrated that the use of CMX, a high-conductivity coverglass, may help to mitigate differential charging and prevent arc-induced contamination. Finally, radiofrequency observations by the Arecibo 305 m telescope of GEO satellites with different configurations have registered abundant arcing of satellites utilizing less conductive coverglasses and no arcing on two with CMX coverglasses. It is the object of the current study to see how space weathering of different coverglass types may alter these results.