Preliminary Assessment Of Site Diversity Schemes For Earth-Space Optical Links

Free Space Optical (FSO) links enable high-speed data transfer from Earth Observation satellites or deep space (DS) probes directly to ground stations. The presence on-board of remote sensing instruments with ever increasing accuracy and resolution fuels the need for transmitting large amounts of data. This contribution investigates the impairments to optical beam propagation due to clouds by exploiting radiosonde observation (RAOBS) data collected in two European sites. Long-term yearly statistics of path attenuation are calculated by first distinguishing between different cloud types and, afterwards, by integrating their contribution to the total attenuation along each vertical profile of RAOBS data. Finally, the effectiveness of a site diversity scheme, simultaneously employing both FSO links, is assessed. Results indicate that a dual-site diversity FSO system with target availability of 10% would require approximately a 40-dB fade margin to counteract cloud attenuation.