Recent solar fare activity and its effect on in-orbit solar arrays

Three major solar proton events (August 12, September 29, and October 19, 1989) have occurred thus far in the 22nd solar cycle. The in-orbit solar array performance of 11 geosynchronous spacecraft was analyzed to determine the effects from these events. The observed degradation was compared to predicted degradations using the flux energy spectra given by the GOES 7 detectors. The observed in-orbit performance degradation to the solar array varied from 2 to 5% for current at a given voltage, depending on the type of solar cell, cover-glass thickness, and length of time in orbit