Atacama Large Millimeter Array Observatory

The Atacama Large Millimeter/submillimeter Array (ALMA) Observatory is an astronomical facility that operates a large array of radio telescopes designed to observe radiation at millimeter and submillimeter wavelengths. By detecting this portion of the electromagnetic spectrum, ALMA enables scientists to study cold objects in the universe such as molecular clouds, dusty star‑forming regions, and the early epochs of galaxy formation. The observatory provides data and observing time to researchers from around the world, supporting a broad range of astrophysical investigations. Its primary service is the collection, calibration, and distribution of high‑resolution astronomical images and spectra.

ALMA is situated on the Chajnantor plateau in the Atacama Desert of northern Chile at an altitude of about 5,000 meters, a location chosen for its exceptionally dry and stable atmospheric conditions. The facility comprises sixty‑six high‑precision antennas that can be rearranged to achieve baselines ranging from 15 meters to 16 kilometers, giving it variable angular resolution. It is a collaborative project involving partners from Europe (represented by ESO), North America (represented by the National Radio Astronomy Observatory), East Asia (represented by the National Astronomical Observatory of Japan), and the Republic of Chile. This international partnership makes ALMA one of the largest and most ambitious ground‑based astronomical endeavors currently in operation.

The observatory’s distinguishing attribute is its specialization in millimeter/submillimeter astronomy, a wavelength regime that is poorly accessible to other telescopes due to atmospheric absorption and technological challenges. ALMA combines exceptional sensitivity with angular resolution that can exceed that of the Hubble Space Telescope at these wavelengths, allowing it to image structures such as protoplanetary disks and the innermost regions of active galactic nuclei. Its sophisticated correlator processes signals from all antennas in real time, producing data products that are made available through a dedicated science archive. These capabilities have positioned ALMA as a leading tool for investigating the cold and dense components of the cosmos.

Operational oversight of ALMA is provided by the Joint ALMA Observatory (JAO), which is managed by the European Southern Observatory on behalf of the international partners, while the host country Chile supplies the site and infrastructural support. The observatory does not have a single parent company; instead it is governed by a cooperative agreement among the participating agencies and institutions. Funding and policy decisions are shared among the partners, ensuring that scientific priorities reflect the interests of the global astronomical community. This collaborative governance model has enabled ALMA to maintain continuous operation and to recover from incidents such as the 2022 cyberattack that temporarily disrupted its website and email services.