European remote sensing satellite (ERS) was the European Space Agency's first Earth-observing satellite programme using a polar orbit. The first satellite was launched on 17 July 1991 into a Sun-synchronous polar orbit at an altitude of 782–785 km.

ERS-2 has been operating without gyroscopes since February 2001, resulting in some degradation of the data provided by the instruments. The tape drive aboard failed on 22 June 2003, leaving the instruments operating only within visibility of a ground station. Since the tape drive failure, additional ground stations have been brought online to increase the data-gathering abilities of the satellite. The Wind Scatterometer and GOME were the only instruments of their kind until the launches of MetOp-A and Envisat, respectively.