The Copernicus Sentinel-1 Earth Radar Observatory, a mission funded by the European Union and developed by ESA, is a constellation of two C-band radar satellites. The satellites have been conceived to be a continuous and reliable source of C-band SAR imagery for operational applications such as mapping of global landmasses, coastal zones and monitoring of shipping routes. The Sentinel-1 satellites are built by an industrial consortium led by Thales Alenia Space Italia as Prime Contractor and with AIRBUS Defence and Space as SAR Instrument Contractor. The first of the two satellites has finalized its environmental test campaign and is now ready for launch on 3 April 2014. The paper describes the general satellite architecture, its key performance as well as its environmental qualification.