would be viewed by many ground observers, those conditions that were thought to produce the brightness ground irradiance were selected for evaluation. For the most part, only normal operations with controlled orientations were assumed; however, two out-of-control abnormal orientations were also treated. A summary of ground irradiance levels that have been calculated is rpesented in the table. The large size of the Space Power System elements would cause even diffuse reflections to appear as very bright light source. As presently designed, vehicles would be held together by beams, painted with highly reflective material. However, the dominant surfaces for reflected light would be the solar panels of the OTV and SPS. These areas would consist of highly specular, low reflectivity cover glass over (lark absorbing cells on the front side and shiny aluminized plastic dielectric on the back. Consequently, most of the reflected light would be very directional; diffuse reflections would be proportionately much dimmer due to a lack of large diffuse surfaces. The diffuse cases summarized in the table would all be relatively bright in comparison with stellar sources. For example, the SPS in GEO would be comparable to the stellar magnitude of Venus at its brightest. The OTV/SB combination in LEO would be visible during daylight hours but, of course, would be at too low an altitude to be illuminated at night. The specular cases cited in the table would produce much brighter ground illumination. However, this irradiance would be restricted to small, fast moving spots. The actual duration of these "glints" of specular reflections varies from about one second for the OTV/SB in LEO to two minutes for the SPS antenna. An important consideration would be the sudden onset of the specular irradiance compared to the much dimmer 5 diffuse irradiance. Enhancements of 10 are common. An exceptionally bright specular reflection would be produced by the backside of the OTV solar panels during LEO construction. Although perfectly flat solar panel surfaces were assumed as worst cases for the OTV and SPS, more realistic situations would be represented by the curved or misaligned surfaces that was also analyzed. The truly abnormal conditions that out-of-control vehicles would create were also cited for completeness. There would undoubtedly be many safeguards in the orbit mechanics to prevent such an occurrence.
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