Editing Atacama Large Millimeter Array (section)

==Overview==

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The initial ALMA array is composed of 66 high-precision antennae, and operates at [[wavelength]]s of 3.6 to 0.32 millimeters (31 to 1000&nbsp;GHz).<ref>{{Cite web|url=https://www.eso.org/public/teles-instr/alma/?lang|title=ALMA - Atacama Large Millimeter/submillimeter Array|website=www.eso.org}}</ref> The array has much higher sensitivity and higher resolution than earlier [[submillimeter astronomy|submillimeter telescopes]] such as the single-dish [[James Clerk Maxwell Telescope]] or existing interferometer networks such as the [[Submillimeter Array]] or the ''[[Institut de Radio Astronomie Millimétrique]]'' (IRAM) [[Plateau de Bure Interferometer|Plateau de Bure]] facility.

The antennae can be moved across the desert plateau over distances from 150 m to 16&nbsp;km, which gives ALMA a powerful variable "zoom", similar in its concept to that employed at the centimeter-wavelength [[Very Large Array]] (VLA) site in [[New Mexico|New Mexico, United States]].

The high sensitivity is mainly achieved through the large numbers of antenna dishes that make up the array.

The telescopes were provided by the European, North American and East Asian partners of ALMA. The American and European partners each provided twenty-five 12-meter diameter antennae, for a subtotal of fifty antennae, that compose the main array. The participating East Asian countries are contributing 16 antennae (four 12-meter diameter and twelve 7-meter diameter antennae) in the form of the Atacama Compact Array (ACA), which is part of the enhanced ALMA.

By using smaller antennae than the main ALMA array, larger fields of view can be imaged at a given frequency using ACA. Placing the antennae closer together enables the imaging of sources of larger angular extent. The ACA works together with the main array in order to enhance the latter's wide-field imaging capability.

===History===
[[File:ALMA Site (artist's impression).jpg|thumb|left|An artist's impression of ALMA]]

ALMA has its conceptual roots in three astronomical projects: the Millimeter Array (MMA) of the United States, the Large Southern Array (LSA) of Europe, and the Large Millimeter Array (LMA) of Japan.

The first step toward the creation of what would become ALMA came in 1997, when the [[National Radio Astronomy Observatory]] (NRAO) and the [[European Southern Observatory]] (ESO) agreed to pursue a common project that merged the MMA and LSA. The merged array combined the sensitivity of the LSA with the frequency coverage and superior site of the MMA. ESO and NRAO worked together in technical, science, and management groups to define and organise a joint project between the two observatories with participation by Canada and Spain (the latter became a member of ESO later).

A series of resolutions and agreements led to the choice of "Atacama Large Millimeter Array", or ALMA, as the name of the new array in March 1999 and the signing of the ALMA Agreement on 25 February 2003, between the North American and European parties. ("Alma" means "soul" in Spanish and "learned" or "knowledgeable" in Arabic.) Following mutual discussions over several years, the ALMA Project received a proposal from the [[National Astronomical Observatory of Japan]] (NAOJ) whereby Japan would provide the ACA (Atacama Compact Array) and three additional receiver bands for the large array, to form Enhanced ALMA. Further discussions between ALMA and NAOJ led to the signing of a high-level agreement on 14 September 2004 that makes Japan an official participant in Enhanced ALMA, to be known as the Atacama Large Millimeter/submillimeter Array. A groundbreaking ceremony was held on November 6, 2003 and the ALMA logo was unveiled.<ref>{{cite web|url=http://www.almaobservatory.org/en/press-room/press-releases/121-ground-breaking-ceremony-for-the-atacama-large-millimeter-array-alma|title=Ground breaking ceremony for the Atacama Large Millimeter Array (ALMA)|author=Alejandro Peredo|access-date=15 November 2014|url-status=dead|archive-url=https://web.archive.org/web/20141111161008/http://www.almaobservatory.org/en/press-room/press-releases/121-ground-breaking-ceremony-for-the-atacama-large-millimeter-array-alma|archive-date=11 November 2014}}</ref>

During an early stage of the planning of ALMA, it was decided to employ ALMA antennae designed and constructed by known companies in North America, Europe, and Japan, rather than using one single design. This was mainly for political reasons. Although very different approaches have been chosen by the providers, each of the antenna designs appears to be able to meet ALMA's stringent requirements. The components designed and manufactured across Europe were transported by specialist aerospace and astrospace logistics company Route To Space Alliance,<ref>{{Cite web|url=http://www.route-to-space.eu/index.php/en/projects/atacama-large-millimeter-array|title=Route To Space Alliance|last=Grieves|first=Shell|website=www.route-to-space.eu|language=en-gb|access-date=2017-02-15|archive-date=2022-01-17|archive-url=https://web.archive.org/web/20220117012844/https://route-to-space.eu/index.php/en/projects/atacama-large-millimeter-array|url-status=dead}}</ref> 26 in total which were delivered to Antwerp for onward shipment to Chile.