y quite hard to displacement damage, certain types of LEDs exhibit significant loss in output power after low levels of proton exposure. Optocouplers also have a wide range of sensitivities to protons dependent on their design, type of LED used and application. As hybrid devices, they also present significant hardness assurance challenges. In all cases, the device response to proton irradiation is found to be very application dependent, which must be reflected in the design of laboratory radiation tests. IV-99 5.0 ACKNOWLEDGMENTS The authors appreciate the consistent support and friendship of colleagues at NASA-GSFC, NRL and elsewhere. Over the years, we have benefited tremendously from technical interchange with Ken LaBel, Robert Reed and Janet Barth. We have enjoyed working with Ed Burke and Al Wolicki on displacement damage issues. They have been an inspiration, and also patient teachers. Martha O'Bryan was indispensable on several fronts including graphics support. 6.0 REFERENCES (All references are unclassified.) [Alur91] M. Alurralde, M. Victoria, A. Caro. and D. Gavillet, "Nuclear and Damage Effects in Si Produced by Irradiations with Medium Energy Protons," IEEE Trans. Nucl. Sci., Vol. 38, No. 6, pp. 1210-1215, 1991. [Amek97] H. Amekura, N. Kishimoto, and K. Kono, "Radiation-Induced Two-Step Degradation of Si Photoconductors and Space Solar Cells," RADECS97, IEEE Doc. No. 97TH8294, pp. 376-381, 1997. [Ando86] K. Ando, M. Yamaguchi, and C. Uemura, "Non-Radiative-Recombination-Enhanced Defect-Structure Transformation in Low Temperature Gamma-Ray-Irradiated InP," Phys. Rev. B. Vol. 34, p. 3041, 1986. [Ansp92] B.E. Anspaugh, "Proton and Electron Damage Coefficients for GaAs/Ge Solar Cells," Proceedings of the 22nd IEEE Photovoltaic Specialists Conference, pp. 1593- 1598, 1992. [Ansp89] B.E. Anspaugh, Solar Cell Radiation Handbook, JPL Publication 82-69, Addendum 1, 1989. [Ansp96] B.E. Anspaugh, GaAs Solar Cell Handbook, JPL Publication 96-9, 1996. [Arim82] I. Arimura and C.E. Barnes, "Proton Damage in Laser D