Radiation environment analysis and effects on optical communication payload for GEO satellite

Abstract

The increasing need of faster data transmission is leading to the spread of optical technologies as the future of space high-speed communication; the potential of this branch of telecommunication is not fully developed, bringing with it both big challenges and great rewards. The purpose of this thesis, developed in the frame of the "Very High Throughput Satellite" project at the Deutsches Zentrum für Luft-und Raumfahrt, is to investigate the Geostationary Earth Orbit (GEO) radiation environment and its effect on optical and electronic COTS devices, as long as consequences on the overall system performance for a free-space optical communication payload. In the first part, an overview of environmental conditions is reported, together with the main models and software exploited in the analysis. Then, a deeper study on system components is carried, with a specific attention on radiation drawbacks on those more susceptible to the harsh context of the mission: here the main focus is given to Total Ionization Dose (TID) effects, having a major relevance and being those for which more data and models are available. In different components the spotlight is not only on possible issues due to the interaction with particles but also on consequences on the overall communication system, with a consequent deterioration of the optical link. As a conclusion, a Python model is developed in order to simulate the cumulative effect of radiation conditions on the payload for a hypothetical 15 years mission; results show various levels of consequences for different devices, with differences also among electrical and optical apparatuses. The system's response itself is investigated by considering the variation of the overall Signal-to-Noise Ratio (SNR). Moreover, tests are performed to gather data for different shielding thicknesses and exposure time for a more complete analysis.