System design of terabit-per-second capacity low earth orbit optical feeder links

Future space-borne synthetic aperture radar, hyper-spectral imaging, and high spatial and temporal resolution imaging will place increasing demands on space network data throughput. It is expected that space data relay systems will require capacities of multiple Terabits per second (Tbps). Free-space optical communication is likely the only technology capable of supporting these data demands. A previous study1 has shown that implementing these high-capacity optical feeder links through a traditional geostationary constellation will pose significant development challenges. Meshed satellite constellations in low earth orbit (LEO), operating at significantly shorter ranges, were shown to have the potential to support Tbps feeder links using the technical capabilities of current free-space optical communication systems. Meshed LEO constellations, however, provide unique challenges, including complex constellation maintenance, dynamic meshing and data routing, and short contact periods with ground stations. We review the design requirements for high capacity LEO relay optical terminals and satellites. The global coverage and ground station downlink opportunities of constellation options are evaluated to develop constellation designs utilizing the minimum number of satellites while providing required feeder link performance. The constellations are designed to provide mesh links with Tbps feeder link capabilities using optical terminals comprised of components within current state-of-the-art and with demonstrated capabilities. These meshed feeder link constellations were then modelled to demonstrate the ability of a LEO constellation to gather Tbps of data over a global network, relay this information around the constellation, and downlink this data to a limited number of ground stations.