For photographic detectors the situation is, of course, more severe. As seen from KPNO, the contaminated zone extends from declination -28° to +14° and now would include the Virgo cluster, which as the nearest example of a regular cluster of galaxies plays a critical role in extragalactic astronomy and is a cornerstone in the cosmological distance scale. The contaminated zone also would extend dangerously close to the North Galactic Pole (NGP). In a region around the NGP the blockage due to dust and confusion by galactic stars is at a minimum, and thus the polar regions provide irreplaceable windows within which the large-scale structure of the Universe can be observed. Thus, if we consider only the diffusely reflected light under ideal conditions, the effects of the SPS are disagreeable for photon detectors and would seriously limit the use of photographic plates or any other detector with finite signal-to-noise ratios. Unfortunately, even at good sites observing conditions are often not ideal. The addition of aerosols or presence of thin clouds, which would produce a minor effect on observations taken against the natural night sky, would increase the level of scattered light. It should be emphasized that even a factor of two increase in the scattered light from SPS would produce an unacceptably large contaminated zone, even for photon detectors. It therefore is likely that the SPS would lead to a reduction in efficiency due to the loss of imperfect nights for faint object work. Similarly, if the brightness of the satellites were to be increased by even a factor of two over mv = -4.3 (which would occur near midnight for a cosine distribution of reflected light), then even under ideal atmospheric conditions 1/4 or more of the prime observable region would be lost. There would also be a number of secondary effects. Obviously, the brightness level of ambient light would increase, necessitating improved shielding and instrument design. In addition, scattered direct light from the satellites within the telescopes and by the observatory building can produce an additional source of unwanted background light, with the unpleasant potential for being non-uniform across the telescope's field of view. The background of both direct and scattered light would be time-varying and is, therefore, difficult to remove. Finally, scattering processes become more severe
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