The POLDER instrument (POLarization and Directionality of the Earth’s Reflectances) conceived by CNES was designed to study the properties of clouds and aerosols, and their major impacts on climate, by analysing the light reflected from Earth and its atmosphere.

Developed by CNES in collaboration with the LOA atmospheric optics laboratory in Lille, the POLDER instrument was designed to study clouds and aerosols, which are known to play a key role in the climate system. POLDER analyses the intensity and direction of light reflected by the Earth and its atmosphere, as well as its polarization, a physical characteristic describing how waves propagate. Such measurements reveal the properties of clouds and aerosols, thereby telling us more about how they affect climate.

There have been three successive generations of instruments: POLDER 1, 2 and 3. POLDER 1 and POLDER 2 were launched on the Japanese ADEOS and ADEOS 2 satellites on 17 August 1996 and 14 December 2002. Unfortunately, both satellites encountered serious technical hitches that brought their mission to a premature end. With POLDER 3 on the other hand, which departed Earth on 18 December 2004 on the French Parasol microsatellite, CNES teams were able to exploit the instrument’s full potential. The Parasol mission continued to operate up to the end of 2013, exceeding its planned design life by more than 5 years.