The Atacama Large Millimeter Array is situated on the Chajnantor plateau 5,000 meters above sea level in the Atacama Desert of northern Chile. This specific site was selected for its high elevation and low humidity to reduce noise and decrease signal attenuation caused by Earth's atmosphere.
Atacama Large Millimeter Array operates as an international partnership among Europe, the United States, Canada, Japan, South Korea, Taiwan, and Chile. The project began as a collaboration between the National Radio Astronomy Observatory and European Southern Observatory before expanding to include other global partners.
Antennae were delivered to the Atacama Large Millimeter Array site from December 2008 to September 2013. The array has been fully operational since March 2013 despite various interruptions including strikes and cyber attacks.
Sixty-six antennae now compose the main array of the Atacama Large Millimeter Array while the Atacama Compact Array enhances wide-field imaging capability. Three prototype antennae underwent evaluation at the Very Large Array since 2002 before full deployment.
The Atacama Large Millimeter Array contributed to the Event Horizon Telescope project producing the first direct image of a black hole published in 2019. It also released studies detailing chemical distribution inside comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON) on the 11th of August 2014.