The ERS satellites's (European Remote Sensing) main mission is to observe Earth, in particular its atmosphere and ocean. Build by Esa, the European Space Agency, they carry several instruments, including a radar altimeter.

ERS-2 was launched in April 1995 as the follow-on from <link internal-link>ERS-1, with which it was used in tandem from August 1995 to June 1996, their identical orbits (35 days) having a one-day shift. 
In June 2003, ERS-2's onboard tape recorder used for the altimeter data has experienced a number of failures. This means that altimeter data are unavailable except for when the satellite is within visibility of Esa's ground stations over Europe, North Atlantic, the Arctic and western North America.
In July 2011, ERS-2 is put out of service by bringing down to a lower orbit. These deorbiting procedures are done while the fuel is still sufficient to make the careful manoeuvres.
Launched in March 2002, the <link _top internal-link>Envisat satellite is the follow-on to <link internal-link>ERS-1 and ERS-2.