A series of European Earth-observation satellites with a remote-sensing facility. The European Space Agency (ESA) launched ERS-1 in 1991 and ERS-2 in 1995 to observe land surfaces, oceans, and polar caps. The extensive data collected by the satellites was used by over 2 000 scientists to forecast weather, monitor crops, and to assess climate trends, marine pollution, and the destruction of tropical rainforests. The spacecraft also monitored natural disasters, such as earthquakes and floods.

The satellites, which worked in combination for about a year, were succeeded by ESA's Envisat. ERS-1 ended its life in 2000 after running out of fuel, having lasted three times longer than predicted. In July 2011, ERS-2 was retired and the process of deorbiting the satellite began. Both satellites carried an active microwave instrument (AMI), a radar altimeter, and an along-track scanning radiometer. A global ozone measurement experiment was added to ERS-2.