LIMITATIONS OF THE BRIEFING DOCUMENT'S CHARACTERIZATION OF THE SPS REFERENCE SYSTEM G. M. Stokes Virtually all of the major effects of the SPS on optical astronomy, infrared astronomy and aeronomy arise from what can be called the passive properties of the SPS. That is to say, the effects are not a result of what the system does, but rather a result of the simple existence of the system. The characterization of the Reference System in the Briefing Document represents our best estimate of what a 60-satellite system will look like. In order to assess the effects of the passive properties of the system on astronomy and aeronomy, it is important to understand the limitations of the Briefing Document assessments. The effect of primary interest, i.e., the increase in diffuse sky brightness, has origins in both the system design and the propagation of light through the atmosphere. There are at present four areas in which the Briefing Document description may be subject to alteration: 1. The Albedo Estimate - The adopted value of 4% may be wrong by as much as a factor of two. Values in the range 2 to 10% have been quoted and no real estimate exists of the change in albedo as the system is aged through micrometeoritic bombardment. 2. The Satellites Here the Only Structures Considered - One feature of the reference system is a low Earth orbit (LEO) support area. This structure or structures could be very bright, and because of its orbit, it would be a great detriment whenever visible. 3. Glints from the Support Structure - In computing the apparent visual magnitude of the system, a contribution from specular glints from the support structures were not included. Their effect may be large.
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