A 12-m antenna for submillimetre astronomy, jointly owned by the Max Planck Institut für Radioastronomie, Onsala Space Observatory, and the European Southern Observatory (ESO), sited at an altitude of 5100 m on the Chajnantor plateau, Chile. It works at wavelengths between 0.2 and 2 mm and began operation in 2005. APEX is a forerunner of the Atacama Large Millimeter/submillimeter Array at the same site.

http://www.apex-telescope.org/ Official telescope website.