exceptionally bright specular reflection is produced by the backside of the OTV solar panels during LEO construction. Although perfectly flat solar panel surfaces are assumed as worst cases for the OTV and SPS, more realistic situations are represented by the curved or misaligned surfaces that are also analyzed. The truly abnormal conditions that out of control vehicles would create are also cited for completeness. There would undoubtedly be many safeguards in the orbit mechanics to prevent such an occurrence. It is noteworthy that at most the enhancement is only threefold in LEO and 15-fold in GEO beyond normal controlled operations. Some perspective on the relative importance of these irradiance levels can be derived by a comparison with the solar irradiance. Insolation is 2 about 1400 W/m , substantially greater than any of the reflections. However, the sun is an extended source subtending 32 arc minutes, whereas the OTV in LEO subtends 11 arc minutes (500 km altitude) at the most, and well beyond LEO both OTV and SPS subtend less than one arc minute, the resolution of the eye. Thus, the power density in this direct solar image would be as much as 10-fold less than that for the CTV in LEO, and 1000-fold less than the OTV and SPS in GEO. Apparent stellar magnitudes provide another useful basis for comparison. Using the sun as the standard, the formula for the visual magnitude of a light source is given by where H is the ground irradiance. Thus, for example, diffuse reflection from SPS in GEO (02) has an apparent magnitude of -3.6, and specular reflection from the SPS antenna in GEO (S3) has a magnitude of -13.8, comparable to the full moon. The methodology for calculating sky brightness created by a diffuse source is also presented. This calculation requires elaborate tabular entries that are given in Table 4. The sky irradiance for a typical set of observation directions, displaced a reasonable angular distance away from the source, is on the order of 1% of the direct irradiance from the source. The sky brightness for other observation conditions should be evaluated on a case by case basis using the tables.
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