The main body of ACTRIS is the distributed observation platform, consisting of observation stations strategically located in diverse climate regimes in Europe and outside Europe, and operated (or co-operated) by ACTRIS partners. Many observation stations belong to one or several European and international networks, such as EMEP, NDACC, GRUAN, or GAW, and are possibly partly shared with other environmental infrastructures, such as ICOS, SIOS, or ANAEE. A typical ACTRIS National Facility is equipped with state-of-the-art instrumentation for the measurement of variables governing the atmospheric radiation balance above Europe.
Measurements of all relevant components are obtained via a combination of in situ and remote-sensing systems and include: i) near-surface measurements of aerosols and short-lived trace gases; ii) vertically resolved measurements of aerosols; iii) vertically resolved measurements of clouds and precipitation; iv) profile and column observations of short-lived trace gases; and v) measurements of a variety of supplementary meteorological and radiation quantities. Besides observation platforms, ACTRIS also includes exploratory platforms at the national level. This category includes laboratories, but also the ability to perform exploratory research in connection with the observational platforms. ACTRIS National Facilities are essentially funded by the member states.