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Ers
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Launched and operated by the European Space Agency, the ERS satellites are the first missions acquiring commercially available microwave radar data, offering new opportunities for all-weather remote sensing applications. The radar images are independent of lighting or weather conditions, while other instruments measure wave height and frequency, wind speed and direction. 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.
ESA plans to launch ENVISAT in 2002, carrying advanced versions of the SAR and ATSR instruments, plus several new sensors.
Acquisition Modes
and Reference Systems
Both ERS satellites were launched into a sun-synchronous orbit at an inclination of 98° 52’ and an altitude between 782 and 785 km. During the tandem phase (from 21/4/1995 to 10/3/2000) ERS–2 was flown 1 day behind ERS–1, and in an orbit offset a few hundred metres, to allow similar acquisition conditions for stereo imaging and interferometry.
The ERS-SAR Reference System is based on a regular grid of tracks (501) and frames. Successive tracks are counted in a continuous non-repetitive way to give a unique value for the orbit which identifies both a track and the relative acquisition date.
Low Bit-Rate (LBR) data are typically global products, and are provided on a yearly (or a 35 day cycle) basis.
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