Space environment effects on solar arrays measured by the PASP plus experiment

On 11 August 95, after about one year in orbit aboard the APEX satellite, the Photovoltaic Array Space Power Plus Diagnostics (PASP Plus) experiment completed its in-situ collection of data on space environmental effects on solar arrays. Its 70° inclination, 2550 km by 363 km elliptical orbit permitted both the investigation of space radiation effects on array power output from passage through the inner radiation belt (apogee region) and the investigation of space plasma effects on array high-voltage operation (arcing at negative voltages and leakage current at positive voltages) in the ionosphere (perigee region). PASP Plus tested twelve types of arrays, some subdivided into electrically separate modules. Of the 16 modules, ten were subjected to positive and negative biasing up to +500 V and -500 V. The solar arrays, interactions measuring instrumentation, and diagnostic sensors are described. Regarding radiation-induced output-power degradation, it was found that arrays with GaAs on Ge cells suffered less degradation than Si-cell arrays. The InP-cell array had the least degradation of the planar arrays, while the Mini-Dome concentrator had the least degradation (7%) of all. The worst power loss (42%) was for amorphous Si, due more to solar-UV degradation than radiation damage. It was found that array configurations where the cell interconnects and side-edges are shielded from the space plasma (i.e., the concentrator arrays or planet arrays with “wrap-through” connectors) have lower are rates under negative biasing and lower leakage current under positive biasing