The ERS-1, 2 satellites are intended for global measurements of
sea wind and waves, ocean and ice monitoring, coastal studies and
land sensing using active and passive microwave remote
sensing systems. ERS-1 was launched in July 1991 and ERS-2
in April 1995.
ERS-1 uses a synthetic aperture radar (SAR) instrument to acquire images
of ocean, ice and land regardless of cloud and sunlight conditions.
Other microwave instruments measure sea state,
sea surface winds, ocean circulation, sea and ice levels, as
well as the sea's surface temperature.
The near polar sun-synchronous orbit of the satellite
enables a global mission providing world-wide geographical and repetitive
coverage, primarily oriented towards ocean and ice monitoring, but
with an all-weather high resolution microwave imaging capability over
land and coastal zones.
ERS-2 is practically identical to ERS-1, with the addition
of the GOME sensor
for global ozone monitoring. The orbits of ERS-1 and 2 are such
that ERS-2 follows the same
ground track as ERS-1, except for a 1-day delay. This provides an
opportunity to obtain
tandem interferometric data of an area using the
synthetic aperture radar on the two
satellites. The tandem data has better coherence property
than the data obtained from
35-day repeat passes of a single satellite. The tandem mission was operational from April to June, 1996 after the launch of ERS-2. ERS-1 has outlived its planned operational life and was deactivated after the tandem mission. Currently, only ERS-2 remains in active operation.
|Type ||Sun-Synchronous |
|Altitude ||782 km |
|Inclination ||98.5 deg |
|Period ||100 min |
|Repeat Cycle ||35 days |
- AMI (Active Microwave Instrument): The AMI operating at
a frequency of 5.3 GHz (C-band, VV-polarised) combines the
functions of a Synthetic Aperture Radar (SAR) and a Wind Scatterometer
(WNS). Through its set of
four antennae (three for the Scatterometer and one for the SAR -
see the figure above), the Earth's surface is
illuminated and the backscattered energy is received to produce data on
wind fields and wave spectra (WNS mode), and to produce high resolution
images (SAR mode) of the Earth's surface.
- RA-1 (Radar Altimeter): The Radar Altimeter measures variations in the satellite's height above sea-level.
- ATSR (Along Track Scanning Radiometer): This passive
instrument monitors the thermal emission of the seas and oceans, from which
the global sea surface temperature is derived.
- GOME, on ERS-2 (Global Ozone Monitoring Experiment): The GOME is a passive spectrometer for monitoring the ozone content of the atmosphere.
ERS SAR Instrument Characteristics
|Frequency ||5.3 GHz (C band)|
|Polarisation ||Linear VV|
|Bandwidth ||15.55 MHz |
|Peak power ||4.8 kW |
|Antennae size ||10 m x 1 m |
|Incidence angle ||23o nominal |
|Swath width ||100 km |
|Resolution ||30 m (azimuth), 26.3 m (range) |
Link to: ESA Earthnet (http://earth.esa.int/).
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