SRC-530

Satellite Power System (SPS) Brightness Due to Reflected Sunlight; DOE/ER-0081; October 1980

Commissioned by U.S. Department of Energy, Office of Energy Research, Satellite Power System Project Division; Under Contract No. 31-109-38-5448. Who paid for a study is recorded because it bears on how its conclusions should be read, not because it makes them wrong.

Published claims resting on this source

• CLM-1162 A satellite would look like Venus all night, and for two minutes near the equinoxes its polished transmitter would flash a full-moon-bright spot 350 km wide across the ground at 150 km a minute; the ferries being built in low orbit would flash brighter still by day. Tilting or curving the panels and roughening the antenna face would cut the glints, though not the Venus-like glow.
• CLM-1163 Between the spring conference paper and the autumn final report, Boeing's figure for how bright a satellite would glow at night fell twelve-and-a-half-fold, from ten times Venus to about Venus, and the report does not say why; the factor is almost exactly what a 4-pi slip in the diffuse-reflection formula would give.
• CLM-1164 The report's worry was not that a satellite could light the ground like the sun. It was that a small bright point in a dark sky reaches an eye whose pupil is wide open. So it compared the brightness of the image on the retina with the sun's: in normal operation the transfer vehicles in low orbit reached about a tenth and the satellites far less. For an out-of-control satellite, a case the report treats as abnormal, the same comparison gives about three-tenths (the record's own arithmetic).

Cite this