Founded as a European version of NASA (the National Aeronautics and Space Administration) in 1975, the European Space Agency (ESA) has followed its own path and has succeeded in federating 17 European countries of which France, Germany, Italy, and the United Kingdom are dominant. In terms of budget, ESA resembles roughly one-fifth of NASA, with an annual spending power of approximately €3 billion compared to the $16.2 billion of NASA. In addition, ESA's mandate is restricted to civilian space programs only. Still, ESA has been able to position itself as a strong number two in this ranking of space agencies, mostly because the ESA has pursued a very comprehensive and ambitious space science program over the last two decades. When "Horizon 2000" was launched in 1984, ESA had managed to launch only three space science missions, COS-B, IUE, and Exosat. However 11 more missions followed by 2001 - all in all 17 spacecrafts. And if one includes the four doomed Cluster satellites of the maiden Ariane 5 flight, the mass of the launched space probes adds up to 30 tons. Horizon 2000 was such a successful space science program that ESA extended it to "Horizon 2000 Plus" in 1994. Consequently six more missions had been launched as of 2001 and 13 others are in preparation. ESA is now starting its next set of activities. At the last ministerial conference in December 2005 in Berlin, the new space science program dubbed "Cosmic Vision 2020" was launched, as well as an ambitious space exploration program named "Aurora," which has the goal of sending humans to the Moon and on to Mars - and this is where NASA enters the picture again.