ction annealing [Keav93]. However, as noted in the case of GaAs LEDs and laser diodes, the degree of annealing characteristic of a particular device needs to be carefully confirmed in a well designed ground test of the flight lot. Note that the amorphous Si cell has been shown by Srour et al. to degrade primarily by TID effects, which is not surprising due to the disordered nature of the material [Srou98]. At very high fluences, minority carrier devices begin to show the effects of carrier removal, and solar cells are no exception. The rapid degradation of solar cell output power at high displacement damage doses illustrated in figure 27 and is due to carrier removal. In fact, failure of a Si solar cell flown in an elliptical orbit through the Van Allen belts from carrier removal effects has been observed [Yama96, Amek97]. Recent work by Messenger et al. has investigated the response of InP solar cells to high proton fluences (including carrier removal effects) [Mess97a, Mess98]. IV-96 Crystalline GaAs/Ge Amorphous Silicon Silicon Displacement Component 1.E+06 1.E+07 1.E+08 1.E+09 1.E+10 1.E+11 1.E+12 1.E+13 1.E+14 Displacement Damage Dose (MeV/g) Figure 27 Maximum power output degradation versus displacement damage dose for a variety of solar cells. The amorphous Si curve includes the displacement component only, and does not include ionization induced degradation. After [Srou98]. Since solar cell performance degrades as a result of displacement damage the analysis tools presented in sections 2.3 and 2.4 can be applied to perform on-orbit predictions. For example, these techniques have been used to predict the on-orbit power degradation of GaAs solar cells due to a solar proton event [Mess97b]. Since these devices are flown in space with very thin shielding (e.g., coverglasses as thin as 3 mil), the lower energy portion of the proton spectrum contributes the bulk of the displacement damage. Note that the deviations of the damage factors from the GaAs NIEL dependence (see figure 9) are less significant in perform