The ATSR Project



What is ATSR?

ATSR stands for Along Track Scanning Radiometer. They are imaging radiometers that provide images of the Earth's surface from space.

Each ATSR instrument has been designed for exceptional sensitivity and stability of calibration, which are achieved through the incorporation of several innovative features in the instrument design. This design has, among other things, enabled the accurate measurement of sea surface temperature to an accuracy of +/- 0.3K!

Four channel

The ATSR channels are at wavelengths of 1.6um (visible) and three thermal bands at 3.7um, 11um, and 12um.

Dual view

Satellite measurements of the temperature of the surface of the Earth are inevitably affected by the passage of the radiation through the atmosphere. The dual view design of ATSR makes it possible to estimate and correct for these atmospheric effects. The two views result from the instrument's conical scanning mechanism. Each scan takes readings from the nadir position and then sweeps round to take measurements from a point about 900Km along the satellite's track. A few minutes after acquiring the forward view, the satellite passes over the same spot and takes readings for the nadir view. As the two views of the same scene are taken through different atmospheric path lengths, it is possible to calculate a correction for the effect of atmospheric absorption.

Self calibrating

Rather than relying on pre launch calibration, the ATSR instrument has two on-board black bodies at known temperatures. Radiation from these is measured during each scan and used to provide a continuous re-calibration of the instrument. This makes it possible to determine single channel equivalent temperatures correct to +/- 0.05K.

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Page last modified : Tuesday, 04-Dec-07