Data Transmission Technologies and Relay Systems in the Copernicus Sentinel Program

This paper analyses the communication architecture and data transmission strategies used within the Copernicus Sentinel program, with emphasis on the integration of optical inter-satellite links and RF systems. A comparative technical assessment highlights advantages and limitations of traditional ground station links versus advanced relay-based approaches, especially the European Data Relay System (EDRS). Special focus is given to the operation of Laser Communication Terminals (LCTs), limitations of Ka-band downlink, and dependencies on satellite orbit, weather, and data volume. The paper identifies key bottlenecks, such as rain-induced attenuation in high-frequency RF channels and explores how new optical technologies and planned relay nodes (e.g., EDRS-E) aim to overcome these. European developments are compared to global systems like Japan’s JDRS and NASA’s retiring TDRSS. The paper outlines pathways to enhance the speed, autonomy, and resilience of satellite data delivery supporting environmental monitoring, emergency response, and research.