Very Large Array

A radio telescope dish at Soccorro, New Mexico, USA. This particular site contains the VLA or Very Large Array, in which 27 dishes are so arranged and linked that they simulate the capabilities of a single dish 27 km/17 mi in diameter. Each dish in the VLA is 25 m/82 ft in diameter.

Largest and most complex single-site radio telescope in the world. It is located on the Plains of San Augustine, 80 km/50 mi west of Socorro, New Mexico. It consists of 27 dish antennae, each 25 m/82 ft in diameter, arranged along three equally spaced arms forming a Y-shaped array. Two of the arms are 21 km/13 mi long, and the third, to the north, is 19 km/11.8 mi long. The dishes are mounted on railway tracks enabling the configuration and size of the array to be altered as required.

Pairs of dishes can also be used as separate interferometers (see interferometry), each dish having its own individual receivers that are remotely controlled, enabling many different frequencies to be studied. There are four standard configurations of antennae ranging from A (the most extended) through B and C to D. In the A configuration the antennae are spread out along the full extent of the arms and the VLA can map small, intense radio sources with high resolution. The smallest configuration, D, uses arms that are just 0.6 km/0.4 mi long for mapping larger sources. Here the resolution is lower, although there is greater sensitivity to fainter, extended fields of radio emission.