Very Large Array

The Very Large Array (VLA) is a radio astronomy observatory located on the Plains of San Augustin, between the towns of Magdalena and Datil, some fifty miles (80 km) west of Socorro, New Mexico, USA. The VLA stands at ,

at an altitude of 6970 ft (2124 m) above sea level. It is a component of the National Radio Astronomy Observatory (NRAO).

Characteristics

The observatory consists of 27 independent radio antennae, each of which has a dish diameter of 25 meters (82 feet) and weighs 209 metric tonnes (230 tons). The antennae are arrayed along the three arms of a Y-shape (each of which measures 21 km/13 miles) long. Using the railroad tracks that follow each of these arms – and that, at one point, intersect with U.S. Highway 60 at a level crossing – and a specially designed lifting locomotive, the antennae can be physically relocated to a number of prepared positions, allowing aperture synthesis interferometry with a maximum baseline of 36 km (22.3 miles): essentially, the array acts like a single antenna with that diameter. The highest angular resolution that can be reached is about 0.05 arcseconds.

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: in other words, once the massive efforts needed to move two dozen 230-ton highly sensitive scientific instruments have been made, the antennae are not moved again for a period of three to four months.

The Array Operations Center (AOC) for the VLA is located on the campus of New Mexico Tech in Socorro. 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 Hawai'i in the west to the U.S. Virgin Islands in the east that constitutes the world's largest dedicated, full-time astronomical instrument.

Past and future

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.

With a view to upgrading the venerable 1970s technology with which the VLA was built, recent funding has been allocated for the conversion of the VLA into the Expanded Very Large Array ("EVLA"). The upgrade will enhance the instrument's sensitivity, frequency range, and resolution, and will install new hardware at the San Agustin site. In addition, up to eight additional dishes in other parts of the state of New Mexico, up to 300 km away, will be constructed and connected to the hub via fiber-optic links.

Popular culture

The VLA is the setting of the beginning of Arthur C. Clarke's novel/film Odyssey Two ^*.

The VLA also featured prominently in Carl Sagan's 1985 novel/film Contact, albeit expanded to 131 dishes and renamed the "Argus Array." When the time came for Hollywood to make the motion picture version (Contact, 1997), much of the outdoor footage was shot at the VLA site. The number of dishes visible on screen was artificially increased by means of CGI, however, and the canyon depicted as being in the vicinity of the VLA is actually Canyon de Chelly in neighboring Arizona.

In the 1996 film Independence Day the alien invaders were initially detected by the VLA.

Visiting

The VLA site is open to visitors year round during daylight hours. A visitor center houses a 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 onsite, 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.

Named after the Very Large Array

The Very Small Array

External links

NRAO VLA – official site.
Photo from Astronomy Picture of the Day

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Radio telescopes | Interferometers | Multiple aperture telescopes | Astronomical observatories in New Mexico | Big Science