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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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