NANTEN2 Observatory, Radio telescope in Atacama Desert, Chile

NANTEN2 Observatory is a 4-meter millimeter and submillimeter radio telescope on Pampa la Bola beside Cerro Chajnantor, at 4,800 m in Chile's Atacama Desert. Its primary mirror is made of carbon-fiber-reinforced plastic with an aluminium-coated reflective surface, and it uses a Cassegrain optics with a 0.5-meter secondary mirror on an altazimuth mount.

The telescope operated at Las Campanas Observatory from 1995 to 2004 before relocating to its current site. This move took advantage of the superior conditions offered by the high desert location.

The observatory brings together research institutions from Japan, South Korea, Germany, Australia, and Chile working side by side on astronomy. This international partnership reflects how modern science crosses borders to study the sky.

The site is not open to the public, so there is no visitor access to the telescope itself; results are presented in lectures organised by Nagoya University and Nagoya City Science Museum. Observers stay at a base camp office in the Sequitor area of San Pedro de Atacama, below the 4,800 m Pampa la Bola site.

The nickname NANTEN ("northern sky") was chosen by public competition when the telescope moved to Chile in 1996, a playful contrast with the southern sky it actually surveys. After a 2004 upgrade at Pampa la Bola it became NANTEN2, with a dome and fully automatic control. Its 4 m primary mirror is carbon-fibre reinforced plastic with an aluminium-coated surface.