FIGURE 1. Apparent Satellite Positions for 60-Sattel1ite System as Seen from Three Major Observatories If we assume the maximum brightness of individual satellites is equal to that of Venus, mv = -4.3, then observatories located in longitudes 70° to 130° will experience some deterioration in quality of dark-time observing. The additional sky brightness from SPS for these observatories would exceed the average dark sky brightness, mv - 22/sq. second of arc, for a zone which crosses the meridian and covers more than 70° in hour angle and up to 10° in declination. This zone would have a sharply peaked ridge of emission centered on the apparent position of the array of satellites, such that within a 3° wide band the sky is five times brighter than dark night sky and within ±20 minutes of arc the effect is more than 10 times that of the dark sky. When the specularly reflected beam from the microwave-transmitting antenna is illuminating ground features or part of the atmosphere visible from an observatory, multiple scattering (or single scattering when the beam passes overhead) can contribute additional diffuse sky brightness. The magnitude of this effect has not been calculated, even for the best case of a dust-free
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