Site diversity: A promising technique to counteract cloud attenuation on 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 huge amounts of data. This contribution investigates the impairments to optical beam propagation due to clouds by exploiting concurrent radiosonde observation (RAOBS) data collected in three European sites. Long-term yearly statistics of path attenuation are calculated by first discriminating 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 dual-site diversity schemes is evaluated: results confirm that this approach is necessary to achieve an acceptable system availability.