With a single concentrator mounted on top of the satellite, the deployment can be very simple, essentially this design only requires the petals of the solar concentrator to be deployed. On the other hand, using side mounted concentrators requires first, that each of the concentrators be deployed away from the satellite before the petals are deployed. Mounting the concentrator on top of the satellite is also very efficient at utilizing the Energia fairing volume, since the payload height is much higher than the payload width. In the side mounted configuration, the envelope of the stowed concentrators restricts the size of the satellite (a 6 m diameter) although it may be possible to accommodate the stowed containers on top of the platform. Therefore the selected concept is to have a single concentrator mounted on top of the satellite as shown in Figure 10.3.11. With this configuration, the solar concentrators must always be pointed at the Sun with the phased array pointed at the Earth. To do this it is required that the attitude control subsystem be used to rotate the spacecraft around the orbit so that the phased array remains Earth facing. The concentrator requires a 0.1“ pointing accuracy towards the Sun from the spacecraft to maintain a good efficiency. Figure 10.3.11 Schematic of a Satellite in Orbit Radiator Configuration To reject the waste heat, a large area of radiators is required. Conventional flat radiators have been proposed which directly radiate the heat into space. Heat pipe radiators being very efficient and a relatively mature technology have been baselined. It has been estimated that -120 m^ of area will be required. This may be achieved by using three of the four large sidewalls of the platform. The fourth side is taken up with the phased array assembly. Using this approach each of the sidewalls will be 4m wide by 10m long retaining partial commonalty with the baseline design. This gives the required 120 m^ of radiator area. The large concentrator will also act as a shield for the radiators from the solar radiation, maintaining the high efficiency of the heat rejection process. Phased Array Configuration The phased array design is different from the baseline since for this option, the phased array is mounted on the sidewall rather than the top floor of the satellite. It is proposed that the basic structure of the satellite by a rectangular box with each side being 4 m by 10 m. This would easily fit within the Energia fairing. It is proposed that the phased array would consist of three sections, each 3.3 m by 10m, two of which are deployed in-orbit so that the required total size of 10m by 10m is achieved. These phased arrays sections could be stowed against the radiator walls during launch since they of similar size. This has the advantage of providing thermal insulation of the radiator walls during the transfer orbit.
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