The European Remote Sensing satellites ERS-1 and ERS-2, launched in 1991 and 1995 respectively, carried a comprehensive payload including an imaging synthetic aperture radar, a radar altimeter and other powerful instruments to measure ocean surface temperature and winds at sea. The two were designed as identical twins with one important difference: ERS-2 included an extra instrument to monitor ozone levels in the atmosphere.

At their time of launch the two ERS satellites were the most sophisticated Earth observation spacecraft ever developed and launched by Europe. These highly successful ESA satellites collected a wealth of valuable data on Earth’s land surfaces, oceans and polar caps and were called upon to monitor natural disasters such as severe flooding or earthquakes in remote parts of the world.