European Space Agency (ESA), European space and space-technology research organization founded in 1975 from the merger of the European Launcher Development Organisation (ELDO) and the European Space Research Organisation (ESRO), both established in 1964. Members include Austria, Belgium, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Luxembourg, the Netherlands, Norway, Poland, Portugal, Romania, Spain, Sweden, Switzerland, and the United Kingdom. Slovenia is an associate member. Cooperative agreements have been signed by various countries, including Canada (1981), which participate in some ESA projects. Headquarters of the agency are in Paris.

Representatives of ESA’s member nations form the agency’s policy-making council. A science program committee established by convention deals with matters related to the mandatory science program; other such bodies may be formed by the council to assist in decision making. The chief executive and legal representative of ESA is the director general, assisted by an inspector general and the directors of various departments.

The principal components of the organization are (1) the European Space Research and Technology Centre (ESTEC), located in Noordwijk, Netherlands, which houses the satellite project teams and testing facilities and is the agency’s main space science and technological research centre, (2) the European Space Operations Centre (ESOC), located in Darmstadt, Germany, which is concerned with satellite control, monitoring, and data retrieval, (3) the European Space Research Institute (ESRIN), located in Frascati, Italy, which supports the ESA Information Retrieval Service and the Earthnet program, the system by which remote sensing images are retrieved and distributed, (4) the European Astronaut Centre (EAC), located in Cologne, Germany, which is a training centre, and (5) the European Space Astronomy Centre (ESAC), located in Villafranca del Castillo, Madrid, Spain, which holds scientific operations centres as well as archives. ESA also operates the Guiana Space Centre (CSG), a launch base in French Guiana.

ESA has cooperated with the U.S. National Aeronautics and Space Administration (NASA) on many projects and, on its own, was responsible for the Giotto space probe, which enabled examination of the core of Halley’s Comet in 1986. ESA also developed the Ulysses spacecraft (launched 1990) to explore the Sun’s polar regions and the Ariane series of launch vehicles, and it established a system of meteorological satellites known as Meteosat. At the beginning of the 21st century, ESA launched the Mars Express orbiter and its lander, Beagle 2. With the launching of the Columbus laboratory on the International Space Station in 2008, ESA became a full partner in the operation of the station. In 2009 ESA launched Planck, a satellite that is designed to study the cosmic microwave background, and Herschel, an infrared observatory that is the largest telescope in space.