The European Southern
Observatory (ESO) project was initiated on Oct. 5, 1962, by five European countries. Six nationsÑBelgium,
Denmark, France, Germany, the Netherlands, and SwedenÑnow participate. Administrative headquarters are in Garching, near Munich. The
observatory, at La Silla, Chile, 960 km (600 mi) north of Santiago, has several
reflectors, a Schmidt, and a large radio telescope. (ESO also manages other telescopes for national institutes.) By the early 21st century ESO plans to complete the Very Large Telescope (VLT) at Cerro Paranal, farther north. Its four 8.2-m (323-in) reflectors will be able to serve, in combined mode (VLTI), as a 16.6-m instrumentÑthe largest effective diameter of any optical telescope. The first of these reflectors (VLT-UT1) began operating successfully in May 1998.