ALMA Observatory

Atacama Large Millimeter/submillimeter Array

One of the world’s largest ground-based astronomy projects, with 66 antennas spread across the Chajnantor Plateau at 5,000 meters. The operations support base is open to free public tours on weekends.

The Atacama Large Millimeter/submillimeter Array (ALMA) was built in cooperation with the European Southern Observatory (ESO), the US National Radio Astronomy Observatory, and the National Astronomical Observatory of Japan. It became fully operational in 2013. Its 66 high-precision antennas, 7 and 12 meters in diameter, are spread across the Chajnantor Plateau at about 5,000 meters. Together they form a “virtual telescope” up to about 16 kilometers across, used to study the formation of galaxies and the birth of stars and planets. ALMA also contributed to the first black hole image released in 2019. The antenna array sits on a plateau too high for public access. However, the Operations Support Facility (OSF) at about 2,900 meters offers free public tours on Saturdays and Sundays. You take the official bus from San Pedro and visit the control room, where you can see astronomers operating the antennas in real time, the antenna maintenance area, and the exhibits. The whole trip takes about 3 to 4 hours. Places are very limited and must be booked on the ALMA website about two months in advance. Bring your passport. If you want to see the stars, San Pedro has several specialist stargazing tours that use large telescopes and explain the southern constellations, the Milky Way, and the Magellanic Clouds. They work best around the new moon, and some tours are cancelled when the moon is full. The desert gets very cold at night, so bring a warm coat. The coordinates given are for the Operations Support Facility (OSF).

ALMA Observatory

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