Constellation Study for Optimized Target Access and Coverage

Abstract

We have performed a low earth orbiting satellite constellation design parameter space study to determine optimized constellations that satisfies mission goals while minimizing total system costs. Because this is a generic study, we developed a generalized set of mission requirements that would meet the needs of several different types of space missions. Figure of merit parameters were defined to help rank the different constellations under study. Instead of performing a full, multi-dimensional parameter space study, we instead focused on a few exemplar cases. For this generic mission, the baseline requirements were as follows: altitude: 700km, total number of satellites per constellation: 40-100, world coverage: 100% coverage or maximize coverage of populated latitudes, polar coverage: some but not 100% required, multi-ball observations: 2- & 3-ball coverage desired, and target coverage: full coverage or up to 5 minute observing gap for 1-ball coverage at all latitudes. For added conservatism, the minimum target observing elevation angle was 10-degrees and the minimum acceptable time on target was 1 minute. We also only performed the calculations for a Walker constellation (defined as M/M/IP or #planes/# satellites per plane/interplane satellite spacing) instead of “streets-of-coverage” constellations, which at high inclinations can satisfy coverage requirements with slightly fewer satellites.