CERSAT > Information > Satellites > Polar orbiting satellites > ERS-2

ERS-2

Description

Platform ERS-2 Summary The ERS Program (European Remote Sensing satellite system) of the European Space Agency is one of the most essential part of an important european earth observation program concerning : meteorology, climatology, oceanography, land resource management...ERS-2 is the second of two twin earth observing satellites launched by ESA respectively in July 1991 and April 1995. It included, in addition to other instruments, several sensors relevant for oceanography such as the RA radar altimeter (measurement of the sea surface topography, the wave height,...), the AMI-Wind scatterometer (measurement of the surface wind speed and direction over the ocean), the SAR (measurement of wave spectra) and the MW micro-wave sounder (brightness temperature, atmospheric vapour content,...). Despite a reduced coverage since the failure of an onboard recorder in 2001, and an initially expected lifetime of three years, it is still operational, providing (together with ERS-1) an impressive 15-years continuous and homogeneous series of sea surface parameters could be collected all along the mission. Agency ESA Orbit polar orbiting (altitude 800 km) Launch date 1995-04-21 End of mission Status Operational Involvement of CERSAT As an element of the ERS ground segment, the CERSAT archives, processes and distributes the data of the onboard radar altimeter, scatterometer and microwave sounder.

Plateform

Largely identical to ERS-1, the plateform is based on the design developed for the French SPOT satellite. Payload electronics are accomodated in a box-shaped housing on the plateform, antennas are fitted to a bearing structure.

Sensors

The ERS-2 mission is essentially turned to the multi-year monitoring of oceans, ice zones and coastal regions. Its platform carries active instruments which measure physical parameters such as significant wave heights, wind speeds and directions, or sea surface temperature. It includes one more instrument (GOME) compared to ERS-1, which makes its mission larger than ERS-1's one. Moreover, for 9 months in 1995-1996, ERS-1 and ERS-2 were operated on the same track on day apart for the tandem mission.

ERS-2 carries instrumentation consisting of a core set of active microwave sensors supported by additional, complementary instruments :

• An Active Microwave Instrument (AMI) combining the functions of a Synthetic Aperture Radar (SAR in image and wave mode) and a Wind Scatterometer. The SAR operates in image mode for the acquisition of wide-swath, all weather images over the oceans, polar regions, coastal zones and land. In wave mode, the SAR produces imagettes (about 5 km x 5 km) at regular intervals for the derivation of the length and direction of ocean waves. The Wind scatterometer uses three antennae for the measurement of sea surface wind speed and direction.
• A Radar Altimeter (RA) providing accurate measurements of sea surface elevation, significant wave heights, sea-surface wind speeds and various ice parameters.
• An Along-Track Scanning Radiometer (ATSR) and Microwave Sounder (MW) combining infrared and microwave sensors for the measurement of sea-surface temperature, cloud top temperature and cloud cover and atmospheric water vapour.
• A Precise Range and Range Rate Equipement (PRARE) for the accurate determination of satellite position and orbit characteristics, and for geodetic 'fixing' of ground stations.
• A Laser Retro-Reflector (LRR) enabling measurement of satellite position and orbit using laser ranging stations on the ground.
• A nadir-scanning ultraviolet and visible spectrometer (GOME, Global Ozone Monitoring Experiment), that enables the measurement of the ozone content of the atmosphere and to monitor changes in vegetation cover.

In short, the ERS-2 platform contains complementary instruments allowing observations of Earth with high accuracy, in all weathers, night and day.

Ground segment of ERS

The ERS Ground Segment was designed by ESA to provide services and to satisfy user requirements for products. CERSAT , as the French Processing and Archiving Facility, is one component of this complex ground segment.

The main elements of the ERS ground segment are :

• Earthnet ERS Central Facility (EECF) in Italy, carries out all user interface functions, including cataloguing, handling of user requests, payload operation planning, scheduling of data processing and dissemination, quality control of data products and system performance monitoring.
• Mission Management and Control Centre (MMCC) in Germany carries out all satellite operations control and functionnal management, including overall satellite and payload operational scheduling. It also controls the Kiruna ground station.
• ESA ground stations at Kiruna (Sweden), Fucino (Italy), Maspalomas (Canary Islands, Spain), Gatineau and Prince Albert (Canada). These stations provide the main network for data acquisition and the processing/dissemination of fast-delivery products.
• National ground stations around the world will receive ERS high rate data by arrangement with ESA, extending the coverage potential of the SAR imaging mission.
• Processing and Archiving Facilities (PAFs) located in Germany, France, Italy and the UK are the main centres for the generation of off-line precision products and the archiving and distribution of ERS data and products.
• User centres and individuals, such as national and international meteorological services, oceanographic institutes, various research centres and individual users.