The European Astronaut Corps is a unit of the European Space Agency (ESA) that selects, trains, and provides astronauts as crew members on U.S. and Russian space missions. The corps has 13 active members, able to serve on the International Space Station (ISS). The European Astronaut Corps is based at the European Astronaut Centre in Cologne, Germany. They can be assigned to various projects both in Europe (at ESTEC, for instance) or elsewhere in the world, at NASA Johnson Space Center or Star City.