HIGH-POWER MICROWAVE OPTICS... Since a tophat system is not diffraction limited, the power can be focused into a smaller spot. Redundant safeguards can doubtless be devised to prevent accidental focusing. More complicated optical systems might be devised that would prevent deliberate focusing unless the satellite was rebuilt. In any case, all proposed systems incorporate the retrodirective array concept and thus require an actively cooperating receiver. With a cooperative receiver, even the reference system can produce high microwave intensities on the ground by delivering beams from many satellites to the same place. The large, multibeam satellites proposed here cannot do this so readily, since there are fewer of them, and since each can only deliver a small fraction of its power to a single location. The greater resolution of the aperture augmented system can lower sidelobe power densities, reducing land use or any low-level microwave hazards that may be discovered. Greater resolution permits not only smaller beams, but beams of non-circular cross section, increasing flexibility of rectenna siting. These features reduce objections that have been raised against the reference system. Further, since each satellite can provide a small fraction of the power needs across a continental area, each section of the power grid on the ground need not depend on any one satellite for more than a small fraction of its power supply. This reduces the cost of back-up power supplies needed in case of satellite failure, and softens the effect of satellite eclipse. The mere size of the satellites need not produce institutional difficulties and centralization (the Earth is a pretty big solar power satellite itself). The structural framework and mirrors could be treated as an industrial park supplying certain services. Local utilities could then lease sunlit area for generating facilities (which need not all be of the same type, or installed at the same time), and lease transmitter locations in the focal plane of the mirror corresponding to their ground rectenna sites. Since the focal plane maps whole continents in miniature, FIGURE 2: A ray-optics illustration, showing mirror abberation and the placement of the phased array in front of the zone of confusion. Not to scale.
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