AATSR

IMPORTANT! Click here for completeness diagrams that show the AATSR datasets that may be downloaded.

On 1 March 2002, an Ariane-5 rocket successfully launched AATSR on-board the Envisat satellite - the largest ever built in Europe. Envisat flew in a Sun-synchronous polar orbit. Generally considered to be, in engineering terms, 'the best ATSR yet', AATSR continued to function well for just over 10 years before the failure of Envisat on 8 April 2012 brought an abrupt end to its operational mission.

History and Contributors

The Advanced Along Track Scanning Radiometer (AATSR) was proposed by the Rutherford Appleton Laboratory (RAL) and British Aerospace plc, now Astrium (UK), as an Announcement of Opportunity instrument for ESA's planned Envisat satellite, for which one of the main objectives was to maintain data continuity after ERS-2.

The (then) UK Department of the Environment (DoE) agreed to fund the instrument as it recognised the importance of the data for the Government-funded programme of climate research and prediction at the UK Met Office Hadley Centre. Successor departments have continued to provide funding for essential ongoing AATSR activities. The DoE funded the manufacture of AATSR on the basis that it meet both the AATSR Scientific Requirements and the AATSR Instrument Performance Requirements.

This was an important and innovative step, because it was the first time in the UK that a 'user agency' had assumed funding responsibility for a new Earth Observation sensor. As with the two previous ATSR instruments, the (then) Australian Space Office made a significant contribution to the building of AATSR.

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AATSR Attributes

As its name implies, this sensor embodies some improvements over its predecessors, the principal of which is that it is able to transmit all the data that it acquires, whereas ATSR-2 had needed to reduce the information content of the data-stream from the new channels, in order to comply with data-rate limitations imposed by the ERS-2 mission. Also, the AATSR embodied substantial redesign of the structure as well as a different closed-cycle cooler system and reference blackbodies, both of which had become available commercially since the start of the ATSR programme.

A key feature of the AATSR is it's in-flight calibration, particularly the three infrared channels. The AATSR conical scan allows the detectors to view a sequence of five elements, as shown in the figure below.

The five elements are:

  1. The along-track Earth view
  2. A hot black-body target
  3. The visible calibration unit
  4. The nadir Earth view
  5. A cold blackbody target.

The two black-body calibration targets observed between the Earth-views are critical to the radiometric quality of the AATSR thermal data. These black bodies use a design concept specially developed for ATSR-1 and are described on the 'What is ATSR?' page.

For the visible and near-infrared channels, a different calibration philosophy is adopted. Here AATSR employs a visible calibration system whereby once per orbit, as the satellite approaches sunrise, a brief view of the Sun is obtained, through a special aperture in the instrument. This is shown in the figure below.

AATSR Visible Calibration System

Instrument design for calibration of visible and near-infrared channels

The solar-view illuminates a diffusing plate made of Russian opal tile, from which the scattered light enters the detector field of view.

During its lifetime, the health of AATSR was continuously monitored by ESA and RAL in accordance with the requirements of the AATSR Verification Plan.

AATSR flight spare on display at Leicester Space Centre

More information on AATSR can be found on the following websites:

AATSR (RAL website)

AATSR (ESA website)

View an image of AATSR on Envisat.

Click to move to ATSR-1 or ATSR-2 or SLSTR.