3. Contamination (p > 2.0) - At this level of light pollution, the option of compensating for increased sky brightness with increased observing time is no longer an option. Figure 1 illustrates the loss of information for observations of galaxies that would result from p > 2.0. These thresholds represent the views of the working group and not the consensus of the astronomical community. We are prepared to justify these values but feel that the general question of acceptability of various degrees of light pollution needs be addressed in a wider forum than the workshop could reasonably be expected to provide. It is important to emphasize that light pollution affects primarily the large, expensive telescopes that are the mainstay of faint object astronomy and that are already severely oversubscribed. The Effects of the Geostationary Orbit for SPS The relationship among the SPS-induced increases in sky brightness, typical astronomical observing programs, and the thresholds for specific impacts on optical astronomy is summarized in Figure 3. The four diagrams in this figure show the outer contours of three light pollution zones described in the preceding section as they would appear at midnight from two major observatories, Kitt Peak National Observatory (KPNO) and Cerro Tololo Inter-American Observatory (CTIO). These two observatories were chosen as representative of the observatories located on the major continental masses of the Western hemisphere. Diagrams 3A and 30 show the computed contours for the set of assumptions described in the Briefing Document. Diagrams 3B and 3D show the contours if the apparent brightness of the individual satellites were increased by a factor of two. The vertical axis in each of these diagrams is declination, the astronomical equivalent of latitude. As the Earth rotates, astronomical objects will appear to rise at the left of these diagrams and move to the right at constant declination. Because the power satellites are in geostationary orbit, the brightness contours will remain fixed in this coordinate system, and astronomical objects at the same declinations will appear to move through these zones of light pollution.
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