Ground Station Network Optimization for Space-to-Ground Optical Communication Links

Space-to-ground optical data links enable higher data rates, require less electrical power, and allow more compact system designs than their corresponding RF counterparts. They may be applied to, for example, downlink Earth observation data from low Earth orbit satellites, or as so-called feeder links for data transmission to geostationary telecommunication or multimedia satellites. However, optical space-to-ground links suffer from limited availability due to cloud blockage. The application of optical ground station (OGS) diversity and thus a network of OGS is required to overcome this limitation. In this paper, we report on OGS networks and the calculation of combined network availabilities. Five years of cloud data gathered by a Meteostat Second Generation satellite have been evaluated. Single-and joint-site statistics as well as correlation between OGS sites are introduced. In order to effectively reduce computational effort, a network optimization method, exploiting the correlation between sites and single-site availabilities, is proposed. Furthermore, the cloud data are used to find several optimal OGS networks and to simulate the networks' availabilities and temporal behaviors. Optimal German, European, and intercontinental networks are identified. With the increasing number of stations, the German network converges to an availability of 84.7%, and the European network to around 99.9%. The intercontinental network even reached an availability of 100% for nine or more stations during the considered time span.