The Very Large Array

PHOTO: by David Finley

"Astronomers have devised ingenious methods of enlarging their signal-collecting area by stretching an array of antennas over miles, even continents. The most sensitive such arrangement is the Very Large Array in western New Mexico. Seen from afar, the 27 white dish antennas look like a fleet of galleons in full sail."

"The operation of each antenna is coordinated with that of the others, carefully timed and processed by computer. The system is able to sort out such fine details as molecules in interstellar space and the halos of matter extending out from visible galaxies. Even more revealing observations are expected from the Very Long Baseline Array now planned as a linkage of radio antennas from Hawaii to Maine and from the Canadian border to Puerto Rico." -- John Noble Wilford

The Very Large Array (VLA) is one of the world's premier astronomical radio observatories. The VLA consists of 27 antennas arranged in a huge Y pattern up to 36km (22 miles) across -- roughly one and a half times the size of Washington, DC.

Each antenna is 25 meters (81 feet) in diameter; they are combined electronically to give the resolution of an antenna 36km (22 miles) across, with the sensitivity of a dish 130 meters (422 feet) in diameter.

1972 August: approved by Congress
1973 April: construction started
1975 September 22: first antenna put in place
1976 February 18: first fringes
1981 January: entire array completed nearly one year ahead of schedule!
The total cost was $78,578,000 (in 1972 dollars), roughly $1 per tax-payer at the time; the project was completed within the allotted budget.

Plains of San Agustin, west of Socorro, New Mexico.

"Although the main thrust has been to listen for radio signals, scientists have not ruled out the possibility that a civilization somewhere might be broadcasting in pulses of light or in streams of neutrinos."

"In 1988, NASA is scheduled to finish a prototype of a frequency analyzer able to distinguish extraterrestrial transmissions from all the natural noise -- including radiation from quasars and certains types of dying stars -- impinging on Earth." -- Richard Flaste

--Wilford and Flast quotations from the New York Times Magazine, 9-16-85

How does it work?
The VLA is an interferometer; this means that it operates by multiplying the data from each pair of telescopes together to form interference patterns. The structure of those interference patterns, and how they change with time as the earth rotates, reflect the structure of radio sources on the sky: we can take these patterns and use a mathematical technique called the Fourier transform to make maps.

Other Kinds of Arrays: A Sound Sculpture/Environment, by David Ferrucci