ALMA Science Archive Atacama Large Millimeter/submillimeter Array

Overview

The ALMA Science Archive (ASA) is the official data repository for observations made by the Atacama Large Millimeter/submillimeter Array (ALMA), an international radio interferometer comprising 66 antennas located on the 5,000-meter Chajnantor plateau in the Atacama Desert of northern Chile. The archive provides astronomers worldwide with access to calibrated and raw ALMA datasets, supporting both ongoing science programs and archival research.

History and Background

ALMA is a partnership of Europe, North America, and East Asia in cooperation with the Republic of Chile, funded by ESO, the U.S. National Science Foundation, Canada, Japan, South Korea, and Taiwan. Planning for the ALMA Science Archive began in parallel with the telescope's construction. The archive's design was optimized for scientific discovery, integrating with the Virtual Observatory (VO) framework. Early Science observations began in 2011, at which point data began flowing from the Atacama site through the Santiago Central Offices to ALMA Regional Centers (ARCs) on four continents. A major version 1.0 milestone of the archive—featuring comprehensive query interfaces, rich metadata, virtual observatory services, browser-based remote visualisation, and Jupyter Notebook tutorials—was described in a 2022 paper in The Messenger.

Collections and Holdings

The archive holds all ALMA observational data, covering radio wavelengths from approximately 0.3 mm to 3.6 mm (frequencies from 84 to 950 GHz across eight observing bands). Data products include raw visibility data, calibrated pipeline products, and value-added science-ready data. The archive is designed to manage the approximately 200 TB of data generated annually by the array. Datasets span a wide range of astrophysical targets including star-forming regions, protoplanetary disks, galaxies, and the cosmic microwave background.

Access and Usage

All ALMA data enter a 12-month proprietary period following delivery to the principal investigator, after which they become publicly available. The archive is accessible at almascience.eso.org/aq/. Users can search by target name, sky position, frequency, spectral resolution, and project, and can retrieve data programmatically via VO services including TAP and VO-Table. The UK ALMA Regional Centre also provides on-demand reprocessing services for archival users.