The University of Tokyo Atacama Observatory (TAO) is an astronomical observatory located on the summit of Cerro Chajnantor, at an altitude of 5,640 m (18,500 ft) within a lava dome in the Atacama Desert of northern Chile. The site is located less than 5 km (3.1 mi) north-northeast of the Llano de Chajnantor Observatory, where the Atacama Large Millimeter Array (ALMA) is located, but is over 580 m (1,900 ft) higher in elevation. The eventual goal of the project is to construct the TAO telescope (or TAO 6.5m telescope), a 6.5 m (260 in) optical-infrared telescope at the site. A first step towards that goal has been the construction and installation of a 1.0 m (39 in) pilot telescope, called miniTAO, completed in 2009. With miniTAO's first light achieved in March 2009 in the visible region, and in June 2009 for the infrared region, the observatory has become the highest permanent astronomical observatory in the world. The high altitude of the observatory is essential for its mission, for it is an infrared light observatory, and infrared light is absorbed by the water vapor in the atmosphere making it imperative that an infrared observatory be located in high altitude where the atmosphere is sparse. In 2023, TAO was noted as one of only a few major telescopes in the world with light pollution below acceptable levels of interference.
