FIGURE 5.4-2, VARYING LENS PARAMETERS Joel Sercel of JPL has pointed out (18) that lightweight microwave reflector designs exist. These relectors could replace the lens design should it prove to be invalid, so the idea of using large effective apertures to reduce SPS size should remain valid. One drawback of a large lens or reflector is that it could block part of the sunlight falling on the SPS. A solution to this problem is to separate the microwave transmitter from the power conversion system by a distance at least as large as the radius of the lens or reflector. This would increase the mass of the structure and the power distribution system. An alternative is to accept the once-daily power decrease. With a lens, the decrease would occur near local midnight. The decrease would be minor because the lens blocks only about 7% of the light. With a reflector, the decrease would occur near local noon, so it would be less acceptable. The optical transmission of microwave reflectors depends on the design, so the decrease might be relatively small.
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