Material considerations in the STEREO solar array design

Solar TErrestrial RElations Observatory (STEREO), the third mission in NASA's Solar Terrestrial Probes program, launched aboard a single Delta II 7925 launch vehicle on October 25, 2006 from Cape Canaveral. This two-year mission employs two nearly-identical, space-based observatories, one ahead of the Earth in its orbit, and the other trailing behind, to provide the first stereoscopic measurements of the sun and its coronal mass ejections, or CMEs. The STEREO observatories utilize four sets of solar arrays, each of which experienced a two-stage deployment on-orbit. This paper illustrates material considerations in the solar array subsystem design. It first focuses on the solar array substrate, considering material coefficient of thermal expansion (CTE) concerns when choosing a substrate laminate to which the solar cells will adhere. It then explores a similar issue when choosing a substrate insert material. Next, the focus shifts to material considerations in the solar array hinge design. This design was driven not just by function, but by a host of different material considerations, ranging from mass savings to fabrication time and cost.