Latest Heat-Sensing 'Eye In The Sky' Completes Testing
Europe's most advanced space-based thermometer for use in climate research has completed its long calibration campaign at the UK's CLRC Rutherford Appleton Laboratory (RAL) in Oxfordshire. The heat sensing instrument, known as the Advanced Along Track Scanning Radiometer (AATSR), is now ready for installation in the European Space Agency's environmental monitoring satellite, Envisat.
AATSR spent many months in a purpose-built space simulation chamber at RAL during a lengthy test sequence to assess its performance. Its seven detectors, which operate at infra-red (heat) and visible wavelengths, were radiometrically calibrated and its optical, thermal and electrical performance was checked. It has now been removed from the chamber and delivered to Matra Marconi Space in Bristol for integration into the giant Envisat.
"These tests have demonstrated that AATSR's performance will exceed that of its predecessors and will keep the UK at the forefront of research into understanding climate change", said Mike Sandford, RAL'S AATSR Project Director.
The new sensor is the third in a series of successful instruments developed in the UK. Its two predecessors, known as ATSR-1 and 2, were installed on the European Remote Sensing Satellites ERS-1 and ERS-2, the second of which is still operational.
The primary objective of the ATSR instruments is to obtain precise measurements of global sea surface temperature. AATSR will be able to measure ocean temperature to an accuracy of better than 0.3C over an area as small as 1 square km with much lower long-term drift.
Since the launch of ATSR-1 in 1991, the instruments have provided a near-continuous dataset of ocean temperature measurements. When combined with the new measurements from AATSR, they will enable scientists to achieve a much better understanding of how variations in ocean temperature may fit in with the pattern of long term changes in our global climate.
Of particular interest will be the large-scale shifts in Pacific Ocean temperatures associated with the periodic El Nino events. As seen during the most recent El Nino of 1997-98, these may lead to drought and forest fires in Indonesia while the west coast of the Americas suffers from violent storms and above average temperatures, with consequent effects on local fishing harvests.
AATSR's capabilities include narrow-band visible detectors which, when viewing land surfaces, will be capable of monitoring changes in vegetation cover and detecting significant changes such as clearing of the rainforests and growth of deserts. It will also assess moisture in vegetation, and, by measuring chlorophyll content, it will be able to determine the growth stage and health of the plants.
Additionally, the visible channels will also be used to measure cloud characteristics, such as the ratio of liquid water to ice, and the particle size distribution. These factors play a major role in determining the amount and type of precipitation.
AATSR is funded by the Department of the Environment, Transport and Regions (DETR), the Australian Space Policy Unit and the Natural Environment Research Council. It was built by the prime contractor, Matra Marconi Space (Filton) with sub-systems supplied by RAL, AEA (Culham), British Aerospace (Australia) and Auspace.
As tall as a three-storey building and with a launch mass of over 8 tonnes, Envisat will be the largest, most complex satellite ever built in Europe. It is due for launch by an Ariane 5 rocket in 2000.
The 101 kg AATSR is one of 10 scientific instruments on board Envisat. It will detect infra-red radiation from the Earth's surface at four different wavelengths and visible light reflected at three visible wavelengths. From Envisat's near-polar orbit, it will cover the surface in 500 km-wide strips as the Earth rotates beneath it.
For further information and images, refer to the RAL Web site at: http://www.atsr.rl.ac.uk/
OR Leicester EOS Group Web site: http://www.le.ac.uk/physics/research/eos/
Contact details are listed above. Images to illustrate articles may be downloaded from the Web site at: http://www.atsr.rl.ac.uk/