The long time-series of observations made by the Along Track Scanning Radiometers (ATSR) missions represents a valuable resource for a wide range of research and EO applications. The ATSRs are multi-channel imaging radiometers with the principal objective of providing data concerning global Sea Surface Temperature (SST) to the high levels of accuracy and stability required for monitoring and carrying out research into the behaviour of the Earth's climate.
The first ATSR instrument, ATSR-1, was launched on board ESA's European Remote Sensing (ERS) satellite, ERS-1 in July 1991. ATSR-1 was followed by ATSR-2, launched on ERS-2 in April 1995 and the Advanced Along Track Scanning Radiometer (AATSR) on ENVISAT in February 2002. Whilst the AATSR mission has now come to an end with the loss of ENVISAT in April 2012, the data from these three missions provides a significant 20+ year data set of global observations in the Short Wave Infra-Red (SWIR) and Thermal Infra Red (TIR) regions. In time, this data set will also be augmented by observations from the fourth ATSR-type instrument, the Sea and Land Surface Temperature Radiometer (SLSTR), to fly on ESA's Sentinel-3 satellite.
With the advent of ESA's Long-Term Data Preservation (LTDP) programme, thought has turned to the preservation and improved understanding of such long time-series, to support their continued exploitation in both existing and new areas of research, bringing the possibility of improving the existing data set and to inform and contribute towards future missions. For this reason, the 'Long Term Stability of the ATSR Instrument Series: SWIR Calibration, Cloud Masking and SAA' project, commonly known as the ATSR Long Term Stability (or ALTS) project, is designed to explore the key characteristics of the data set and new and innovative ways of enhancing and exploiting it.