conversion system and integrated relay antenna or transmitting array sized to about 150 m diameter. Directivity and distance of the relay link are variable, but this link is generally oriented toward the equatorial plane with a range of about 15,000 km.. The relay satellite would have two steerable receiving antennas to accommodate power transmission from different Sun Tower directions, each sized to about 120 m diameter. Received power could be stored on-board or converted directly to microwave frequency (nominally 5.87 GHz) and transmitted to Earth via a planar phased array antenna whose circular diameter is about 240 m. Heat rejection is assumed to be modular and integrated at the backplane of the transmitter array. When the MEO relay satellites are implemented as non frequency-shifting ReflectArrays, as they are in the Phase II baseline concept, the Sun Towers would still require a relay-pointing transmitting antenna/array, but the transmitted power would be at microwave frequencies (2.45-30 Ghz) rather than mm-wave to enable better atmospheric transmission of the “reflected” energy. The diameters of both the transmitting and receiving antenna arrays would have to be increased accordingly (each on the order of a kilometer or more) to effect comparable beam-coupling efficiencies at these lower frequencies. However, this size increase would presumably be offset by the higher efficiency and reduced operational and electronic complexity of the ReflectArray versus a more conventional MEO relay. Figure 3-7 The ReflectArray Relay Satellite Concept
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