| Very Large Array | |
| Organization | National Radio Astronomy Observatory |
|---|---|
| Location | Socorro County, New Mexico, USA |
| Wavelength | radio |
| Diameter | 27 x 25m |
| Angular resolution | 0.05 to 700 arcsec |
| Website | www.vla.nrao.edu |
The Very Large Array (VLA) is a radio astronomy observatory located on the Plains of San Agustin, between the towns of Magdalena and Datil, some fifty miles (80 km) west of Socorro, New Mexico, USA. The VLA has made key observations of black holes and protoplanetary disks around young stars, discovered magnetic filaments and traced complex gas motions at the Milky Way's center, probed the Universe's cosmological parameters, and provided new knowledge about the physical mechanisms that produce radio emission.
The VLA stands at an elevation of 6970 ft (2124 m) above sea level. It is a component of the National Radio Astronomy Observatory (NRAO).[1]
U.S. Route 60 passes through the complex, which is adjacent to the Boy Scout Double H High Adventure Base.
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The observatory consists of 27 independent antennas, each of which has a dish diameter of 25 meters (82 feet) and weighs 209 metric tons (230 Short tons).[2] The antennas are arrayed along the three arms of a Y-shape (each of which measures 21 km/13 miles long). Using the rail tracks that follow each of these arms—and that, at one point, intersect with U.S. Route 60 at a level crossing—and a specially designed lifting locomotive ("Hein's Trein" [3]), the antennas can be physically relocated to a number of prepared positions, allowing aperture synthesis interferometry with a maximum baseline of 36 km (22 mi): in essence, the array acts as a single antenna with that diameter. The smallest angular resolution that can be reached is about 0.05 arcseconds at a wavelength of 7 mm.[4]
There are four commonly used configurations, designated A (the largest) through D (the tightest, when all the dishes are within 600 m of the center point). The observatory normally cycles through all the various possible configurations (including several hybrids) every 16 months; the antennas are moved every three to four months. Moves to smaller configurations are done in two stages, first shortening the east and west arms and later shortening the north arm. This allows for a short period of improved imaging of extremely northerly or southerly sources.[5]
The frequency coverage is 74 to 50,000 MHz (400 to 0.7 cm).[6]
The Array Operations Center (AOC) for the VLA is located on the campus of the New Mexico Institute of Mining and Technology in Socorro, New Mexico. The AOC also currently serves as the control center for the Very Long Baseline Array (VLBA), a VLBI array of ten 25-meter dishes located from Hawaii in the west to the U.S. Virgin Islands in the east that constitutes the world's largest dedicated, full-time astronomical instrument.[7]
In 2011, a decade long upgrade project had resulted in the VLA expanding its technical capacities by factors of as much as 8,000. The 1970s era electronics were replaced with state-of-the-art equipment. To reflect this increased capacity, VLA officials have asked for input from both the scientific community and the public in coming up with a new name for the array.[8][9]
The VLA is a multi-purpose instrument designed to allow investigations of many astronomical objects, including radio galaxies, quasars, pulsars, supernova remnants, gamma ray bursts, radio-emitting stars, the sun and planets, astrophysical masers, black holes, and the hydrogen gas that constitutes a large portion of the Milky Way galaxy as well as external galaxies. In 1989 the VLA was used to receive radio communications from the Voyager 2 spacecraft as it flew by Neptune. It is not, despite depictions in popular culture, used to assist in the Search for Extra-Terrestrial Intelligence (SETI).
The driving force for the development of the VLA was David S. Heeschen. He is noted as having "sustained and guided the development of the best radio astronomy observatory in the world for sixteen years."[10] Congressional approval for the VLA project was given in August 1972, and construction began some six months later. The first antenna was put into place in September 1975 and the complex was formally inaugurated in 1980, after a total investment of USD $78.5 million.[11]
With a view to upgrading the venerable 1970s technology with which the VLA was built, the VLA has evolved into the Expanded Very Large Array (EVLA). The upgrade has enhanced the instrument's sensitivity, frequency range, and resolution with the installation of new hardware at the San Agustin site. A second phase of this upgrade may add up to eight additional dishes in other parts of the state of New Mexico, up to 300 km away, if funded.[12]
The image of the VLA has become nearly iconic in American culture, though most persons do not know where it is located or what exactly it does. But it has appeared in much of pop culture since its construction.
The VLA is located between the towns of Magdalena and Datil, about fifty miles (80 km) west of Socorro in New Mexico. U.S. Route 60 passes east-west through the complex.
The VLA site is open to visitors year round during daylight hours. A visitor center houses a small museum and a gift shop. A self-guided walking tour is available, as the visitor center is not staffed continuously. Visitors unfamiliar with the area are warned that there is little food on site, or in the sparsely populated surroundings; those unfamiliar with the high desert are warned that the weather is quite variable, and can remain cold into April.[13]
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