|
 |
Ers
Sensors
|
Active Microwave
Instrument (AMI)
The AMI comprises two separate radars:
the Synthetic Aperture Radar (SAR), operated
in Image or in Wave Mode, and a Wind Scatterometer.
SAR Image Mode
In Image Mode, the SAR obtains strips of
high-resolution (30 m) imagery, 100 km
wide, to the right of the satellite track.
The 10 m antenna, aligned parallel to the
flight track, directs a narrow radar beam
onto the Earth’s surface over the
swath. Imagery is built up from the time
delay and strength of the return signals,
which depend primarily on the roughness
and dielectric properties of the surface
and the range from the satellite.
SAR Wave Mode
Wave Mode operation of the SAR measures
the changes in radar reflectivity of the
sea surface due to surface waves, and provides
5 x 5 km images of 10 meter resolution
at intervals of 200 km along track. These ‘imagettes’ are
transformed into spectra providing information
about the wavelength and the direction
of wave systems. Series of power spectra
can be used to determine the evolution
of swell wave systems.
Wind Scatterometer
The Wind Scatterometer uses three sideways-looking
antennae illuminating a swath 500 km wide,
giving three independent backscatter measurements
in three different directions, separated
by a very short delay, from which the surface
wind vector can be calculated.
The Wind Scatterometer cannot be operated
in parallel with the SAR in Image Mode
but parallel operation of the wind and
wave modes is possible.
Low Bit-Rate
Sensors
Radar Altimeter
(RA)
A nadir-pointing pulse radar with two measurement
modes to measure the echoes from ocean
and ice surfaces. It operates in the K-band
at 13.8 GHz, with a maximum 10 cm vertical
resolution and a swath width of 1.3°.
Ocean Mode
Used to measure wave height, surface wind
speed and sea-surface elevation – for
the study of ocean currents, tides and
the global geoid.
Ice Mode
Operating with a coarser resolution, Ice
Mode provides information on ice sheet
surface topography, ice types and sea/ice
boundaries.
Along-Track Scanning
Radiometer (ATSR)
The ATSR is a four-channel infrared radiometer
providing measurements of sea-surface and
cloud-top temperatures. The Earth’s
surface is viewed at two different angles
(0° and 52°). Data are combined
to eliminate atmospheric influence in the
calculation of sea-surface temperature.
The ground resolution is 1 km.
Microwave Radiometer
(MWR)
A nadir-viewing passive radiometer providing
measurements of the total water content
of the atmosphere within a 20 km pixel,
used to improve the accuracy of sea-surface
temperature measurements and the Radar
Altimeter.
Global Ozone
Measuring Experiment (GOME)
The Global Ozone Measuring Experiment on
ERS–2 provides a complete world ozone
map every three days. GOME also detects
other trace gases as well as aerosol and
micro-particle pollution in the lower atmosphere. |
| |
|
|
|
|
|
