Tools for Advanced Chain Access Analysis on Satellite Constellations

Free Space Optical (FSO) communication between satellites is a new cutting-edge topic that is gaining more and more popularity, due to its possible advantages with respect to standard radio communication. Another interesting and under development field is the one of satellite constellations. Feeder Links for Non Geo-Stationary Orbits (FL4NGSO) is a joint project between DLR, ESA and Kepler Communications wich aims at studying the coverage and access availability performance of two LEO constellations that use Optical Feeder links and Optical Inter-Satellite Links (OISL). This work will present the main results of the access availability and inter-satellite links analysis, which make the core part of the project. However, the main focus will be on two Python-based performance optimization tools: a Network Optimization tool and a Flexible OISL tool. Across the different sections the reader will see how the access availability performance of each constellation improves by introducing OISL first, and the optimization tools later, as well as the intrinsic differences between constellation A, with a higher orbital altitude and a limited number of satellites, and constellation B, with a lower orbital altitude and a larger number of satellites. It emerged that constellation A needs significantly less OGSs than constellation B to reach an optimal coverage and access availability for all the most important targets. The Flexible OISL tool improves the performance of the constellations by shifting some of the requirements from the ground segment to the space segment, with the net result of reducing the number of OGSs needed to guarantee an operable network. The results obtained were used to conclude the thesis with a trade-off analysis between the two constellations. The conclusion is that the higher altitude constellation is by far more performing for all the trade factors, with the exception of the latency, and is therefore better suited for this project.