The ERS program was composed of two missions, ERS-1 and ERS-2, and it was a pioneering character in the field of instrument development (active sensors).
The mission introduced and demonstrated advanced observation technologies and is a fine example of a European success story.
ERS-2 mission duration: ERS-2 was launched by Ariane-4 on 21 April 1995 and was ended and then de-orbited on 5 September 2011 after 16 years of activity.
The ERS-1 satellite carried five sensors: an Active Microwave Instrument (AMI) including a radar imager (SAR) and a scatterometer, a radar altimeter (RA), a radiometer (ATSR), a microwave sounder (MS) and range equipment (PRARE) - as described in the table below. The ERS-2 satellite carried an additional sensor, the Global Ozone Monitoring Instrument (GOME).
The ERS-1 and ERS-2 missions were mainly operated in a 35-day repeat cycle. In addition, a 3-day cycle (ice phase) was followed by ERS-1 in 1992 and 1994 and by ERS-2 in 2011. ERS-1 had also a 168-day repeat cycle (geodetic phase) in 1994 and 1995. Both ERS-1 and ERS-2 were operated in a 1-day difference (known as tandem mode) from 1995 to 2010 to develop SAR interferometry applications.