that specular reflections be reduced where possible as was also suggested in the Boeing Co. report (14, op. cit.). 2 .0 Statement of the Problem 2.1 Background The Space Power System (ref. 1) now in the concept stage, envisions a large surface of solar cells (SPS) continuously oriented towards the sun while in geosynchronous orbit (GEO). On the opposite side of the satellite will be a microwave conversion and transmission system to convert the photovoltaic energy to microwaves, which will be beamed to receiving stations on earth. A highly reflective, polished circular antenna wil be continuously aimed at the receiving stations. The solar cell surface will be planar and rectangular, and covered with glass, so that it, in effect, is an enormous plane mirror which, if misaligned, could reflect a large proportion of the sun's rays to the earth's surface presenting a potential hazard to observers on earth. The antenna, though not as large, would be intentionally pointed towards the earth and would present specular reflections of a fraction of the solar disc, to an observer on earth for over two minutes at a time. There will be a large staging base (SB) in lower earth orbit (LEO), from which orbital transfer vehicles (OTV) will carry sections of the SPS to GEO for final assembly. The SB, although much nearer earth, has no specular surfaces and probably presents no potential optical hazards. The sections of solar panel carried by the OTVs when in or near the LEO would subtend a relatively large angle from earth and hence reflect a large portion of the solar disc, also presenting a potential hazard to observers on earth. In the following sections, the irradiances on earth and their probable maximum durations will be subjected to a worst case analysis in terms of
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