The satellite sensor measures the infrared radiance leaving the top of the atmosphere towards the satellite ; this radiance is corrected with respect to the influence of a clear (i.e. nearly non scattering) atmosphere ; the resulting radiance is converted to a temperature according to Planck’s law and it is called "Land Surface Temperature" (LST).

The LST is derived from several sensors (METEOSAT, MSG) using various approach, in the framework of projects :
  GEOLAND
  AMMA.