C. Solar Cells and Blankets Figure B-2 shows details of the basic solar cell blank structure. The blanket consists of 50 pm thick single crystal silicon solar cells with borosilicate cover glass electrostatically bonded to the cells front and back. The cells are designed with both P and N terminals brought to the backs of the cells. This feature makes it possible to use 12.5 pm silver-plated copper interconnections which are formed on the substrate glass. Complete panels are assembled electrically by welding together the module-to-module interconnections. Other details and features of the blanket design are shown on figure B-2. The nominal cell efficiency is 17.3 percent (AMO, 28°C) at beginning of life. A key feature of the blanket design is the ability to perform in-situ annealing of the solar cells using a laser annealing concept. Annealing is required to recover radiation induced degradation of the cells. D. Solar Array and Structure Figure B-3 shows the buildup of a solar array fundamental elements, which is a blanket panel. A blanket panel contains 224 solar cells (16 in series by 14 in parallel). Its dimensions are as shown. The blanket panels are assembled into installable blanket segments by welding the interpanel connectors and taping the panels together (see figure B-4). The blanket segments are 14.9 m wide by 656 m long (about one bay length) and are shipped accordion-folded in a suitable box. The method of supporting the solar blanket within the primary structural bays is shown in figure B-4. This method of support will provide a uniform tension to the end of each solar array segment by the use of constant force tensioning springs at each blanket support tape. These springs are also attached to a catenary cable that is then attached to the primary structure, (upper surface), beams at 15 meter intervals. The springs are in compression, for better reliability, and exert a uniaxial force of approximately 3.5N to each blanket support tape. The buildup of high voltage in the solar array is accomplished by connecting approximately 78,000 sets of solar cells in series (a string). Solar cell strings approximately 5.1 km long were selected for the reference
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