Esa Bulletin February 2001 [antikvár]

aatsrAATSR: Global-Change and Surface-Temperature Measurements from EnvisatD. Llewellyn-Jones M.C. EdwardsSpace Research Centre, University of Leicester, United KingdomC.T. Mutlow A.R. BirksRutherford Appleton Laboratory, United KingdomI.J. BartonCSIRO Marine Research, Australia H. TaitSpace Division, Vega Group PLC, United KingdomIntroductionThe monitoring and detection of global climate change is one of the great challenges for modern satellite observing systems. The Advanced Along-Track Scanning Radiometer (AATSR) is one of the Announcement of Opportunity (AO) instruments on ESA's Envisat platform due for launch in mid-2001. It is funded jointly by the UK Department of the Environment, Transport and the Regions (DETR), the Australian Department of Industry,The Advanced Along-Track Scanning Radiometer (AATSR) onboard ESA's Envisat spacecraft is designed to meet the challenging task of monitoring and detecting climate change. It builds on the success of its predecessor instruments on the ERS-1 and ERS-2 satellites, and will lead to a 15+ year record of precise and accurate global Sea-Surface Temperature (SST) measurements, thereby making a valuable contribution to the long-term climate record.The exceptionally high radiometric accuracy and stability of AATSR data are achieved through a number of unique features. A comprehensive pre-launch calibration programme, combined with continuous in-flight calibration, ensures that the data are continually corrected for sensor drift and degradation. A further innovative feature providing substantial advantages over traditional nadir-viewing instruments is the use of a 'dual-view' technique offering improved atmospheric correction. The accuracies achieved with this configuration are further enhanced by using low-noise infrared detectors, cooled to their optimum operating temperature by a pair of Stirling-cycle coolers.With its high-accuracy, high-quality imagery and channels in the visible, near-infrared and thermal wavelengths, AATSR data will support many applications in addition to oceanographic and climate research, including a wide range of land-surface, cryosphere and atmospheric studies.Science and Resources (DISR), and the UK Natural Environment Research Council (NERC) and is the most recent In a series of instruments designed and developed to measure SST to the high levels of accuracy (better than 0.3 K 1 slgma limit) and precision required for monitoring climatic trends and for research Into climate prediction.The AATSR follows ATSR-1, launched on ESA's ERS-1 satellite in July 1991 and ATSR-2, launched on ERS-2 In April 1995. Together, this family of instruments will establish a unique fifteen-year record of global Sea-Surface Temperature (SST) at a level of accuracy previously unprecedented in this field.As an Imaging spectrometer, the (A)ATSR system builds on the multi-channel approach to SST retrieval developed from the NOAA Advanced Very-Hlgh-Resolutlon Radiometer (AVHRR) missions, but offers considerable advantages over other sensors in the form of the unique sensitivity and stability of its calibration. This Is achieved through the use of several innovative features, including:-An along-track scanning technique that provides observations of the same point on the Earth's surface from two different viewing angles, for Improved atmospheric correction.-Continuous onboard calibration of the thermal channels against two stable, high-accuracy black-body calibration targets.-An onboard visible calibration system for the visible and near-Infrared channels (first Introduced on ATSR-2).-Low-noise infrared detectors, cooled by a pair of Stirling-cycle coolers.-A rigorous pre-launch calibration programme.h !11