to a rectenna on the ground. This concept is illustrated in Figure 4. The configuration of the satellite consists of a planar solar array structure built from a graphite composite material. Two conversion options are presented. One is the single-crystal gallium-aluminum-arsenide (GaAlAs) solar cells with a concentration ratio of 2 as illustrated in figure 4. The other energy conversion option is the use of single-crystal silicon (Si) solar cells with no concentration. The size of the solar array is dictated primarily by the efficiency chain of the various elements in the system. Figure 5 shows the end-to-end efficiency chain for the GaAlAs and silicon solar cell options. With the satellite designed to provide 5 GW of DC power to the utility busbar and an overall efficiency of approximately 7%, it is necessary to size the solar arrays to intercept approximately 70 GW of solar energy as indicated in figure 5. The quoted efficiency is the minimum efficiency, including the worst-case summer solstice factor (0.9675), the seasonal variation (.91), and the end-of-life (30 year) solar cell efficiency assuming annealing. For the GaAlAs case, the end- of-life (30 year) concentrator reflectivity is 0.83. Since only half of the intercepted solar energy is reflected by the concentrators, the equivalent overall efficiency is 0.915. The GaAlAs option is a five-trough configuration with a solar blanket area of 26.52 km^, a reflector area of 53.04 km^ and an overall planform area of 55.13 km^. The silicon option has the solar blanket with no concentration resulting in a blanket area of 52.34 km^ and a planform area of 54.08 km^. The satellite in either option is oriented so that the antenna main rotational axis remains perpendicular to the orbital plane. The end-mounted microwave antenna is a one kilometer diameter phased- array transmitter. The phase control system utilizes an active, retrodirective array with a pilot beam reference for phase conjugation. Klystrons are used as the baseline power amplifier with slotted waveguides as the radiating element. The ground rectenna has subarray panels with an active element area of 78.5 km . The satellite is constructed in geosynchronous orbit with construction time being six months. The initial estimates of construction crew size are 555
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