The ERS-1 satellite's main mission was to observe Earth, in particular its atmosphere and ocean. Built by ESA, it carried several instruments, including a radar altimeter.
ERS-1 was launched in July 1991, switched off in June 1996 and retired in March 2000. ERS-2, the follow-on from ERS-1, was launched in April 1995. It was used in tandem with ERS-1 from August 1995 to June 1996, their identical orbits (35 days) having a one-day shift.
ERS-1 flew on three different orbits:
- a 3-day period for calibration and sea ice observation,
- a 35-day period for multi-disciplinary ocean observations,
- a 168-day period for geodetic applications.