The albedo is the fraction of the incoming solar radiation reflected by the land surface, integrated over the whole viewing directions. The albedo can be directional (calculated for a given sun zenith angle, also called "black-sky albedo") or hemispheric (integrated over all illumination directions, also called "white-sky albedo"), spectral (for each narrow band of the sensor) or broadband (integrated over the solar spectrum). The surface albedos are derived from many sensors (VEGETATION, POLDER, METEOSAT) in the frame of different projects :
CYCLOPES GEOLAND POLDER - PARASOL AMMA VGT4AFRICA.