Cloud detection algorithms used in the processing of ATSR data into sea
surface temperature
, by A. M. Zavody, C. T. Mutlow and D. T. Llewellyn-Jones

The cloud detection scheme used at the start of the ERS-1 mission has been
found to have been deficient in a number of cases. Constant monitoring of the
performance of the tests has led to significant improvements. The test based on
the increase of near-infrared radiation over cloudy pixels now  uses the IR
brightness temperatures as well as the sun- and  viewing-angles, leading to
better identification of cloudy pixels in and near areas of sun glint. A new
test which derives  dynamically a threshold for the 11um channel brightness
temperature has increased the detection rate for uniform low level cloud. The
infrared histogram test, using the differences between the brightness
temperatures in the 11um and 12um channels, has ben further improved by the
simultaneous use of the value of the 12um IR brightness temperatures, and by
several refinements for trapping cloudy pixels missed by all the other tests.

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