ATSR-1 was launched as part of the payload of ESA's ERS-1 satellite on 17th July 1991, and was the test-bed for the along track scanning concept.

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.

The ATSR1 instrument has four channels at wavelengths of 1.6um (visible) and three thermal bands at 3.7um, 11um, and 12um.

The ATSR instruments are novel in that they incorporate 2 views into each swath scan. 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.

The ATSR instruments are also 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.