Atacama Large Millimeter Array

Atacama Large Millimeter Array
ALMA Antennas on Chajnantor.jpg
Alternative namesALMA Edit this at Wikidata
ObservatoryLlano de Chajnantor Observatory Edit this on Wikidata
Location(s)Atacama Desert, Antofagasta Region, Chile Edit this at Wikidata
Coordinates23°01′09″S 67°45′12″W / 23°01′09″S 67°45′12″W / -23.0193; -67.7532 Edit this at Wikidata
Atacama Large Millimeter Array is located in Chile
Atacama Large Millimeter Array
Location of Atacama Large Millimeter Array

The Atacama Large Millimeter/submillimeter Array (ALMA) is an astronomical interferometer of 66 radio telescopes in the Atacama Desert of northern Chile, which observe electromagnetic radiation at millimeter and submillimeter wavelengths. The array has been constructed on the 5,000 m (16,000 ft) elevation Chajnantor plateau - near the Llano de Chajnantor Observatory and the Atacama Pathfinder Experiment. This location was chosen for its high elevation and low humidity, factors which are crucial to reduce noise and decrease signal attenuation due to Earth's atmosphere.[1] ALMA is expected to provide insight on star birth during the early Stelliferous era and detailed imaging of local star and planet formation.

ALMA is an international partnership among Europe, the United States, Canada, Japan, South Korea, Taiwan, and Chile.[2] Costing about US$1.4 billion, it is the most expensive ground-based telescope in operation.[3][4] ALMA began scientific observations in the second half of 2011 and the first images were released to the press on 3 October 2011. The array has been fully operational since March 2013.[5][6]

Overview

The first two ALMA antennas linked together as an interferometer
Three ALMA antennas linked together as an interferometer for the first time
ALMA prototype-antennas at the ALMA test facility
Cerro Chascon at sunset
The ALMA correlator

The initial ALMA array is composed of 66 high-precision antennas, and operates at wavelengths of 9.6 to 0.3 millimeters (31 to 1000 GHz). The array has much higher sensitivity and higher resolution than earlier 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 facility.

The antennas can be moved across the desert plateau over distances from 150 m to 16 km, which will give ALMA a powerful variable "zoom", similar in its concept to that employed at the centimetre-wavelength Very Large Array (VLA) site in New Mexico, United States.

The high sensitivity is mainly achieved through the large numbers of antenna dishes that will 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 antennas, that compose the main array. The participating East Asian countries are contributing 16 antennas (four 12-meter diameter and twelve 7-meter diameter antennas) in the form of the Atacama Compact Array (ACA), which is part of the enhanced ALMA.

By using smaller antennas than the main ALMA array, larger fields of view can be imaged at a given frequency using ACA. Placing the antennas 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

On 4 March 2011, ten antennas are installed at Chajnantor.

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 organize 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.[7]

During an early stage of the planning of ALMA, it was decided to employ ALMA antennas 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,[8] 26 in total which were delivered to Antwerp for onward shipment to Chile.

Other Languages
slovenčina: ALMA
српски / srpski: Atacama Large Millimeter Array