III.7 How will SPS's in GEO affect the aesthetics of the night sky? SPS spacecraft would, if built according to the current Reference System design, be visible on clear nights. The visible light from each spacecraft (sunlight diffusely reflected from the solar blanket array) would produce about 1/1000 the light of a full moon; the satellites would be brighter than any object in the night sky except the moon.^ They would be brightest near midnight, comparable to Venus, and would become invisible near dawn or sunset since the large solar arrays would be seen "on edge" at these times.^5 If 60 SPSs were positioned uniformly in GEO over the continental United States, the appearance would be that of a chain of bright planetlike objects extending (as viewed from the U.S.) in a nearly straight line from east to west across much of the southern sky. They would be separated slightly less than are the stars in Orion's Belt. These bright objects would be in fixed position relative to the earth, and stars and planets would thus appear to move from east to west past them. The relative brightness of the satellites, and their consistent spacing would contrast with the random configurations of stars that form the traditional constellations. In addition, use of 7-power binoculars would clearly show them to be rectangular structures rather than points of light. Light from a large number of SPS satellites would brighten the night sky due to atmospheric scattering, and would be of some concern to astronomers. At intervals of six months, the satellites would pass through the earth's shadow at approximately midnight for a number of days in succession: an occurrence something like a lunar eclipse. Satellites would dim and redden on encountering the edges of the shadow, darken, then reappear about 10 minutes later. The earth's shadow could be seen to progress from east to west along the line of satellites. The current Reference System design calls for use of highly reflective material for the satellite transmitting antenna. Specular reflections from the large flat areas of the transmitting antenna would periodically direct bright beams of light across the night side of earth. The reflection would be comparable to the full moon for two SPS Preliminary Environmental Assessment,DOE/ER-0021/2, October 1978. 35 Livingston, L.E., Briefing on Visibility of SPS, presented at NASA JSC, June 6, 1979.
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