Characteristics - ERS
ERS 1
On 17 July 1991, Ariane 44L launched the European Remote Sensing Satellite ERS-1 from its launch pad in Kourou, French Guyana. It was the first European satellite to carry a radar altimeter and was launched into an 800 kilometer altitude and 98.5 degree inclination orbit. During the first few months, the Commissioning Phase, all instruments were calibrated and validated. After that ERS-1 flew two Ice Phases (in which the repeat period was three days), a Multi-Disciplinary Phase (a 35-day repeat orbit lasting from April 1992 until December 1994), and the Geodetic Phase, which started in April 1994 and has a repeat period of 168-days. A second repeat cycle in this Phase, on-going until the launch of ERS-2, was shifted by 8 km with respect to the first so a 336-day repeat is obtained.
From launch, until the satellite's retirement on 10 March 2000, ERS-1 monitored the sea surface almost continuously. The accuracy of its altimeter range measurements has been estimated to be a little under 5 cm.
The European Space Agency's (ESA) first sun-synchronous polar-orbiting mission, ERS-1 made 45,000 orbits, acquiring more than 1.5 million individual Synthetic Aperture Radar (SAR) scenes.
| ERS-1 has the following instrumentation onboard:
1) Synthetic aperture radar |
  Courtesy of Eurimage. |
The duration of the mission has also meant that scientists have already observed several El Nino phenomena through combined observations of surface currents, topography, temperatures and winds. The measurements of sea surface temperatures, critical to the understanding of climate change, made by the ERS-1 Along-Track Scanning Radiometer are the most accurate ever from space. All these critical measurements are being continued and enhanced by the current ERS-2 mission.
ERS-2
ERS-2, the successor of ERS-1, was launched on 21 April 1995. Until the retirement of ERS-1 the satellites orbited in the same orbital plane, with all instruments simultaneously operating.
ERS-2 is similar to ERS-1 and carries very similar instruments, with the addition of the GOME instrument.
| ERS-2 has the following instrumentation onboard:
1) Synthetic aperture radar |
  Courtesy of Eurimage. |
ERS-1 and ERS-2 flew in tandem, meaning that ERS-2 followed ERS-1 in the same orbit (multidisciplinary phase, 35 day repeat cycle). ERS-2 was 24 hours behind ERS-1 (July, 1995), so there is another dimension to temporal resolution, whereby ERS-1 and ERS-2 images cover the same are one day apart. For the first time precise topographic information could be routinely produced from space data using the ERS-1 and ERS-2 tandem operations. ERS-1 operations went into stand-by (campaign) mode in June 1996 and ended on March 13, 2000.
