The Atacama Pathfinder Experiment (APEX) is a radio telescope located at Llano de Chajnantor Observatory in the Atacama Desert of northern Chile. It is a single-dish modified ALMA prototype antenna.
APEX is operated by 3 European research institutes: The Max Planck Institut für Radioastronomie (MPIfR), Onsala Space Observatory (OSO), and the European Southern Observatory (ESO).
The telescope was designed and constructed by the German firm VERTEX Antennentechnik GmbH, under contract by MPIfR.
- Name: Atacama Pathfinder Experiment (APEX)
- Location: Llano de Chajnantor Observatory, Chile.
- Coordinates: 23°00'21.0"S 67°45'33.0"W
- Altitude: 5064 metres
- Telescope type: Sub-millimeter antenna
- Dish diameter: 12 metres
- Telescope optical design: Cassegrain, Alt-Azimuth mount
- First light: 14 July 2005