Contact plan design for GNSS constellations: A case study with Optical Inter-Satellite Links

Abstract

Optical Inter-Satellite Links (OISLs) are being con-sidered for future Global Navigation Satellite System (GNSS)constellations. Thanks to OISLs, the constellation incorporatesimproved clock synchronization and precise ranging among thesatellites, which are essential features to achieve accurate timeand orbit determination. High data rate communications withinthe space segment also reduce ground segment dependency, bymeans of decentralized access to information. However, the dualoptimization of data and navigation performance metrics requiresa careful assignment of OISLs to the available laser communica-tion terminals on-board. To this end, we present a Contact PlanDesign (CPD) scheme based on a Degree Constrained MinimumSpanning Tree heuristic applied to such OISL-enabled GNSS (O-GNSS) constellations. Results on the Kepler system, a novel GNSSproposal, show that a fair distribution of connectivity among theconstellation can be ensured while optimizing its range-basedposition estimation capabilities (PDOP). A PDOP improvementof 85 % is reached on average by the optimized contact plan withrespect to a generic scheduler that disregards the geometricaldistribution of the chosen links.