The AATSR is the latest in a series of European Space Agency (ESA) instruments designed to measure sea surface temperature. The ATSR (Along Track Scanning Radiometer) instruments measure brightness temperature in several infrared channels at a spatial resolution of one kilometre. Although they have been designed primarily to provide accurate sea surface temperature measurements, the data is also useful for scientific studies of the land surface, atmosphere, clouds, and the cryosphere.
ATSR-1 - the first instrument - was launched on board the ESA's European Remote Sensing Satellite (ERS-1) in July 1991.
ATSR-2 - an enhanced version - was launched on board ESA's ERS-2 spacecraft in April 1995. ATSR-2 is equipped with additional visible channels for vegetation monitoring.
AATSR (Advanced Along Track Scanning Radiometer) instrument has been launched on board ENVISAT in March 2002.
Each ATSR instrument has been designed for exceptional sensitivity and stability of calibration, making it possible to measure sea surface temperature to an accuracy of +/- 0.3K.
Channels: The ATSR channels are at wavelengths of 1.6µm (near infrared) and three thermal bands at 3.7µm, 11µm, and 12µm.
Calibration: The ATSR instruments are self calibrating. Onboard are two 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.
Satellite measurements of the Earth's surface temperature are 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.
As the sensor scans the Earth's surface it first 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. Thus two views of the same scene are taken through different atmospheric path lengths, making it possible to calculate a correction for the effect of atmospheric absorption.
AATSR Introduction
This introduction to the AATSR instrument is part of ESA's Envisat pages, which include instrument descriptions and
handbooks for the use of Envisat data.
The ATSR Project
Information about the sensor, processing and data availability from Rutherford Appleton Laboratory.