ERS ATSR and AHVRR spectral characteristics and SST accuracy

Below ATSR and AVHRR spectral bands are shown. Similar spectral channels allow comparative analyses.

ATSR double view, nadir and forward, allows to see the same area twice, within about 2.5 minutes. This feature doubles the information over a given target area, under the assumption of a stable stratified atmosphere. The view angle also varies along the scan. In the nadir view (0 deg.) it varies between 0 and 21 deg. whereas in the along-track view (53 deg.) it varies between 52.4 and 55 deg.. The calibration system includes a "visible calibration unit" (only in the ATSR-2) and two blackbodies for the calibration of the thermal infrared channels. The blackbodies are kept at temperatures representative of the Sea Surface Temperature (SST) upper and the lower values (265 and 305 deg. K). The primary mission objective of the ATSR instrument was to provide Sea Surface Temperature (skin temperature) nevertheless also surface and cloud studies have stemmed from ATSR data.

• ERS ATSR SST accuracy (1 km x 1 km spatial resolution) has been estimated to be about 0.3 deg. K (corresponding approximately to an observational random error of 3 standard deviations). ATSR SST improved accuracy is due to its reduced thermal noise (0.04 deg. K), its cooling system, which maintains the detectors at a given temperature, its better calibration system, its higher digitalization and its dual view.
• A typical accuracy figure of SST derived from the AVHRR sensor is about 0.6 deg. K (McClain et al., 1985).

ATSR SST validation results

McClain, E.P., Pichel, W.G., and C.C. Walton, "Comparative performance of AVHRR based multi-channel sea surface temperatures", J. Geophys. Res., 90, 11, 587-11, 601, 1985.

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry