ERS
The ERS-1 and ERS-2 series of satellites were the first to be launched by the European Space Agency. They provide global and repetitive observations of the environment using advanced microwave techniques that enable imaging to take place regardless of cloud and sunlight conditions.
SAR imagery is ideal for both onshore and offshore particularly where there is persistent cloud cover or poor illumination as it is capable of penetrating cloud, rain, dust and haze allowing data to be collected both day and night. In contrast to optical imagery, SAR is an active sensor. The return signal strength depends primarily on:
- The dielectric property of the surface (e.g. metals reflect more than vegetation)
- The roughness of the surface (e.g. rough versus calm water)
- The slope of the ground imaged
- The range of the ground imaged from the satellite
ERS-1 and 2 have a core set of Active Microwave Sensors and additional complementary instruments to support them:
- Image mode - 100Km by 100Km along track to the right of the satellite
- Wave mode - 5Km by 5Km imagettes to give information on wavelength and direction of wave systems
- Wind mode - 25Km grid spacing, generally used in conjunction with wave mode
- Radar altimetre - Nadir pointing pulse radar providing information on wave height, surface wind speed and sea-surface elevation. Also provides information on ice sheet surface topography
- Along Track Scanning Radiometre (ATSR) - Provides information on sea surface temperature and cloud top temperature
ERS-1 operated regularly from 25/7/1991 to 10/3/2000, ERS-2 started regular acquisitions in May 1995 and it is still operational.
