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The Microwave Radiometer (MWR) -or Microwave Sounder (MWS)- is part of
the Along Track Scanning Radiometer and Microwave Sounder (ATSR)
instrument on-board the European Remote Sensing Satellites (ERS-1 and
ERS-2) launched by the European Space Agency on 17 July 1991 and 20
April 1995.

The ATSR incorporates two separate instruments: an advanced four-
channel infrared radiometer (the ATSR-IRR, commonly called the ATSR)
used for measuring sea surface temperature and cloud top temperatures,
and a two-channel Microwave Sounder (the ATSR-MWR, commonly called the
MWR) designed to measure total precipitable water vapour and the total
liquid water content of the atmosphere.

The MWR is a passive two-channel radiometer. The footprints of the two
channels are not coincident on the Earth's surface, as one channel
views slightly forward of the nadir point and the other slightly
behind, although both are on the sub_satellite track. The footprints
are 22.4 km for the forward view and 21.2 km for the rear view, with a
60 km separation. The calibration is achieved by ambient loads within
the instrument, consisting of terminated waveguides and a set of
skyhorns viewing space.

MWR characteristics:

Channels: 23.8 and 36.5 GHz
Beam width: 3 dB
IFOV: 20 and 22 km
Antenna: 60 cm off-axis paraboloid Cassegrain
Receiver: Dicke

The ATSR was designed to provide the following:

- global sea surface temperature, accurate to better than
0.5K (absolute) with a spatial resolution of 50 Km in
conditions of up to 80% cloud cover
- images of surface temperature, accurate to 0.1K
(relative) with 1 km resolution and 500 km swath width
- total water vapour content of the atmosphere
- observations of clouds, aerosols, haze, land-ice and
sea-ice surface emissivity
- tropospheric range correction of the radar altimeter
measurements to better than 5 cm

The ATSR provides important information in scientific disciplines such
as oceanography, climatology and meteorology. When combined with
observations of cloud top temperatures, cloud cover, haze, aerosol and
total water vapour content of the atmosphere, significant improvements
may be expected in the accuracy of medium range weather
forecasting. Also accurate sea surface temperatures can be of use to a
number of commercial users, particularly those involved in fishing and
the management of fishing areas. In the field of research, potential
applications of the ATSR include distinguishing thin new ice from open
water, identifying surface type, and the accumulation rate of land

Online sensor information:

Related URL:

Reference online documentation:

For any query, please refer to:

ESA/ESRIN Earth Observation Help Desk


Phone: +39 06 94180777

Fax: +39 06 94180292



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