JPSS-1 Solar Array Development   Ball Aerospace was awarded JPSS-1 as a follow on to S-NPP in September 2010. The intention for JPSS1 was for it to be a nearly exact copy, or “clone” of S-NPP. However, one of the differences that directly  impacted the solar array design and accommodation was the inclusion of two TDRSS antennas, one nadir  pointing and the other zenith pointing. Figure 5 shows where the nadir pointing ground antenna was  mounted, where it needed to be stowed between the bus and the solar array. This forced the solar array to  be translated 10 cm (4 in) farther from the bus panel than before. This accommodation was made by  incorporating standoff brackets under the four RRS (Retention and Release Subsystem) brackets and  under the RDA. JPSS-1 took advantage of new cell technology and transitioned to a new type, the “XTJ,”  which increased current so that additional wires were required to cross each inner panel hinge line and the  main deployment hinge line. Also, on JPSS-1, the Gold Rules were tailored in the mission specific  requirements and flowed down to engineering through an Environmental Design and Testing Specification.  Figure 5. JPSS-1 Observatory (Deployed Configuration)  Hinge Design Updates  The issues raised during the S-NPP torque margin investigation were addressed with design updates for  JPSS-1. One significant update addressed a “rule of thumb” of the constant-torque spring vendor to limit  the number of springs in a stack to 3. The width and thickness of the springs were made larger to increase  their torque and reduce the number needed to meet torque margin requirements. The hinges went through  a test program, discussed below, that characterized the drag torques that had to be overcome and satisfy  the torque margin requirements. JPSS-1 had an increase of 32 wires crossing the MDH hinge line and 7  additional wires crossing each IPH hinge line. The number of springs was determined based on the drag  torque measurements. Then these springs were installed on the hinge and tested over the full range of  motion.  Referring to Figure 6, the output drum was increased in diameter and arc length to accommodate the larger  constant-torque spring. Two additional fasteners were added for load carrying capability and the ability to  add a piece of Mechanical Ground Support Equipment (MGSE) that would make manual rotation of the  hinge easier and to allow instrumented torque measurements. The change in the spring design required  more spacing between the output drum and take up roller. The take up roller diameter was increased to  reduce its deflection. An additional Vespel washer was placed between the end of the roller sleeve and the  washer on the end to minimize friction between the roller sleeve and the CRES washer. The MDH axles  were changed from the S-NPP design by eliminating cotter pins from the central area of the MDH where  the RDA harness routes to the connector bracket on the inner panel. This minimized the extent of sharp  edges exposed to the harness. The pawl, not shown, was modified to have a spherical surface that would  engage the bottom of the cam surface at the end of range of motion and would provide a point contact  during lockout.  NASA/CP—2018-219887 394