The interface between the solar array and transmitter consists of a support yoke, a mechanical turntable drive, and an electrical slip ring. The overall yoke arrangement was depicted in Figure 1. Figure 4 shows additional detail of the electrical slip ring. Twenty rings provide conductor paths for the ten pairs of busses. The slip ring diameter was minimized to the extent practicable considering the currents to be delivered, clearance for bus connections, and thermal control. The slip ring size allows it to be assembled and cheeked out on the ground and delivered to orbit intact aboard the reference Heavy Lift Launch Vehicle. The power transmitter includes 101,552 high-efficiency Klystron power transponders each including phase control equipment and power control and data management support systems. The transponders conjugate and amplify the uplink phase control signal from Earth and return it to the point of origin as a power beam. Each klystron is individually phase-controlled to maintain precision beam control and high gain. Three levels of control are provided for beam steering: (1) Coarse mechanical pointing of the antenna by the rturntable drive; (2) Fine mechanical pointing by antenna-mounted CMG's; (3),Ultra-fine electrical pointing by the phase control system. The CMG s are continuously desaturated by the turntable drive; the overall angular momentum control for the satellite is provided by electrical thruster systems at the four corners of the solar array. The antenna power intensity is tapered over the aperture to provide high power transfer efficiency and low sidelobes. The taper ranges from a maximum of 22 kW per square meter at the center of the antenna to 1/9 of this value at the edge, as schematized in Figure 5. The Klystron transponders are assemoled into subarrays 10.4 meters square. The subarrays include the slotted waveguide radiators, distribution waveguides, thermal control equipment, phase control equipment, support structure, and data and control systems. They are designed to be assembled and tested on the ground prior to shipment to space. Most of the electronic complexity of the power transmitter is within the subarrays, thus most of the electronic integration can be done on Earth. Power supplied to the Klystrons must be partially processed. About 85$ of the power can be provided unconditioned from the solar array with only breaker protection. The balance is processed by substations located at the back of the power transmitter. Figure 6 is a preliminary concept of such a substation. The size of the individual processors was selected so that outage of a single processor (and the Klystrons it supplies) will not significantly disturb the power beam pattern. Satellite configuration control and data management are provided by a triply-redundant comunications system interconnected with a redundant, hierarchical, distributed-processing computer network. Triple redundancy of computers is also provided for critical functions such as flight control. All data and communications interconnects employ fiber optics in order to minimize interference from the satellite electrical and RF power systems.
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