The VLA is one of the world's greatest astronomical radio observatories. It consists of twenty-seven 25 m radio antennas in a Y-shaped configuration on the plains of San Agustín in New Mexico at an altitude of 2,124 m. Each arm is 21 km in length (Figure 7.20) and the data from the antennas may be combined interferometrically to give the resolution equivalent to an antenna 36 km across in the facility's highest resolution configuration. Each antenna has a collecting area of 491 m2, giving a total facility collection area of 13,250 m2, equivalent to a single 130 m diameter dish. Construction of the VLA began in 1973, and the facility was formally dedicated in 1980.
The radio dishes of the VLA may be moved on a rail system to take up one of four positions with different maximum separations: A (36 km), B (10 km), C (3.6 km),
Figure 7.20. The Very Large Array (VLA) in New Mexico. Courtesy of NRAO/AUI.
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