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Radiation tests on bare N/P silicon solar cells and solar cells with various cover materials were performed with 1 Mev energy electrons for integrated fluxes up to 1016 e/cm2. The effect of electron irradiation upon the physical, electrical, optical, and thermal characteristics of the cells were analyzed and are presented in parametric form wherever practical. In particular, the changes with electron flux in the electrical output, and the temperature coefficients of the electrical output as well as the effect of the angle of incident radiation upon the output, have been investigated. The variations of spectral transmittance of cover materials and the spectral reflectance at angles of incidence between zero and 75 degrees were measured and the data compared to the electrical measurement results. The solar absorptance as a function of angle of incidence and the hemispherical emittance were calculated. All electrical measurements were performed under illumination closely approximating the spectrum of solar irradiation in outer space, and at the intensity of the solar constant. This is of particular importance when studying the effects of charged particle radiation, since the data thus obtained can be directly utilized for spacecraft solar array design.