Aerosols, these tiny particles of the lower atmosphere, are one important component of atmosphere affecting climate (radiative effects, water cycle) and air quality.

For characterizing and monitoring aerosols, water wapour and clouds, the USA and France developed the AERONET network in the early 1990 years.

This network is composed of automatic sun-photometers (CIMEL CE318) operating in near real time and providing aerosol optical and columnar microphysical properties.

The database started in 1993 and PHOTONS, the French component of the AERONET federation and the leading component of AERONET-Europe (ACTRIS) is managed by LOA, Université de Lille, France.