The POLDER (POlarization and Directionality of the Earth's Reflectances) instrument, developed by the French Space Agency (CNES) has flown on board the ADEOS-1/NASDA platform from November 1996 until June 1997. The sensor has a wide field of view (2400km swath) for collecting global daily data and has multi-angle viewing capability. It measures the solar radiation reflected by the Earth in eight spectral bands. For three of these bands (0.443, 0.670 and 0.865 μm), measurements include the polarization ratio by the use of 3 polarizers. This measurement strategy provides unique information on aerosols, clouds and surfaces.