Assessment of CIEMAT’s Plataforma Solar de Almeria as a Ground Station Site for Optical LEO Satellite Downlinks

Abstract

The Optical Data Downlink Technology from Satellite to Ground requires receiving stations in geographical areas with low cloud probability. In the southern part of Spain, at the site of CIEMAT’s Plataforma Solar de Almeria (close to the city of Almeria), an operational optical ground station is deployed by the German Aerospace Center (DLR), named FOGATA (Free-space Optical Ground station Antenna TAbernas). To predict its availability and data throughput performance, cloud-images taken by an all-sky camera between 08/2019 and 08/2021 have been analyzed in terms of angular cloud position and occurrence. This image data has then been related to exemplary satellite orbits (from the BIROS and AeroCube12B satellites) and their ground visibility was analyzed over the course of a year. The ground visibility is merged with the satellite trajectories and the according link budget is considered. This allows to derive the potential transmission capacity, assuming an adaptive data rate scheme that enables optimum transfer rate for a selection of rate steps. The intermittent blocking of a link passage by confined cloud structures is considered as a further parameter. Future analysis will include the cloud analysis at night-time and its comparison to daytime statistics, as well as the comparison with automated satellite signal observations employing an infrared all-sky camera.