Solar Array Degradation On Geostationary Communications Satellites: The Quantification Of Annual Degradation And Degradation Over Solar Proton Events

Solar array telemetry from eleven geostationary communication satellites, launched between 1990 and 1998, was analysed and used to quantify solar array degradation of gallium arsenide (GaAs) and silicon (Si) solar cells. GaAs cells had an average annual percent degradation ranging between 0.44% and 1.03%, while Si cells had an average annual percent degradation ranging between 0.71% and 1.69%. The decrease in Si cells degradation rates, based on telemetry of I-sc and V-oc levels, similar to 1,210% over a ten years mission suggests an update to the Si solar cell degradation design rule of thumb 25% over a ten year mission. Degradation during solar particle events (SPEs) of 10 MeV proton flux > 10,000 pfu was analysed and used to create an initial functional relationship between degradation experienced over SPEs and the accumulated fluence of these SPEs.