Probability of large solar proton events and their effect on the efficiency of GaAs solar cells

Using a recently, updated database that includes the last four complete sol ar cycles, the probability of occurrence of large solar proton events has b een analyzed for time periods of rep to seven active solar, years using ext reme value statistics, Then an approach is presented for evaluating solar c ell efficiency degradation caused by the large event, These results enable spacecraft designers to evaluate precisely the risk of exposure of solar ar rays to large solar proton events over the course of a mission, As am examp le, the efficiency degradation of n\p GaAs\Ge solar cells caused by an even t dth a > 10-MeV fluence of 1 x 10(10) cm(-2) is shown, This is compared to the degradation resulting from all events in the last solar cycle, and to the electron environment in geostationary orbit over the same period of tim e. (C) 1998 John Wiley & Sons, Ltd.