Low orbiting satellites like Sentinel-1A transmit data to Earth when passing over ground stations in Europe. For continual data delivery, Sentinel-1A is equipped with a laser terminal to transmit data to satellites in geostationary orbit carrying the European Data Relay System (EDRS). These satellites then transmit the data to the ground. Complementing the Sentinel ground-station network, EDRS ensures the timely availability of large volumes of data. Its first node will be launched in 2015.
The EDRS technology is being demonstrated now by a laser terminal hosted by telecom satellite Alphasat, which was launched in 2013. With its help, data is transmitted in near-real time to ground stations in ESA ESOC (Darmstadt, Germany) and DLR German Aerospace Center's GSOC and DFD (Oberpfaffenhofen, Germany).
Sentinel-1A is the first in the family of satellites for Europe’s Copernicus programme, the largest environmental monitoring programme in the world. This new satellite carries an advanced radar to image Earth’s surface through cloud and rain, regardless of whether it is day or night. Among its many applications, Sentinel-1 routinely monitors shipping zones, maps sea ice and provides information on winds and waves for marine traffic, tracks changes in the way land is being used, provides imagery for rapid response to disasters such as floods, and monitors uplift and subsidence.