APEX - the Atacama Pathfinder Experiment

APEX is a collaboration between the Max-Planck-Institut für Radioastronomie (MPIfR) in Bonn (together with Astronomisches Institut Ruhr-Universität Bochum, AIRUB), ESO and Onsala Space Observatory in Sweden (OSO). The idea is to construct and operate a 12-m diameter submillimetre telescope on the ALMA site of Llano de Chajnantor in Chile at an altitude of 5000 m. APEX will operate at submillimetre wavelengths as well as in the far infrared (at THz frequencies), which is possible because of the excellent atmospheric transparency that exists on the site at these wavelengths; it might be the best site in the world for sub-millimetre astronomy.