Very Large Array

The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory in the southwestern United States built in the 1970s. It lies in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, approximately 50 miles (80 km) west of Socorro. The VLA comprises 28 25-meter (82 ft) radio telescopes (27 of which are operational while one is always rotating through maintenance) deployed in a Y-shaped array and all the equipment, instrumentation, and computing power to function as an interferometer. Each of the massive telescopes is mounted on double parallel railroad tracks, so the radius and density of the array can be transformed to adjust the balance between its angular resolution and its surface brightness sensitivity. Astronomers using the VLA have 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 6,970 feet (2,120 m) above sea level. It is a component of the National Radio Astronomy Observatory (NRAO). The NRAO is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

The radio telescope comprises 27 independent antennas in use at a given time plus one spare, each of which has a dish diameter of 25 meters (82 feet) and weighs 209 metric tons (230 short tons). The antennas are distributed along the three arms of a track, shaped in a wye (or Y-shaped) configuration, each of arm measuring 21 kilometers (13 mi) 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"), the antennas can be physically relocated to a number of prepared positions, allowing aperture synthesis interferometry with up to 351 independent baselines: in essence, the array acts as a single antenna with a variable diameter. The angular resolution that can be reached is between 0.2 and 0.04 arcseconds.

There are four commonly used configurations, designated A (the largest) through D (the tightest, when all the dishes are within 600 meters (2,000 ft) 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.

The frequency coverage is 74 MHz to 50 GHz (400 to 0.7 cm).

The Pete V. Domenici Science Operations Center (DSOC) for the VLA is located on the campus of the New Mexico Institute of Mining and Technology in Socorro, New Mexico. The DSOC also serves as the control center for the Very Long Baseline Array (VLBA), a VLBI array of ten 25-meter (82 ft) 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.

In 2011, a decade-long upgrade project resulted in the VLA expanding its technical capacities by factors of up to 8,000. The 1970s-era electronics were replaced with state-of-the-art equipment. To reflect this increased capacity, VLA officials asked for input from both the scientific community and the public in coming up with a new name for the array, and in January 2012 it was announced that the array would be renamed the "Karl G. Jansky Very Large Array". On March 31, 2012, the VLA was officially renamed in a ceremony inside the Antenna Assembly Building.

Upgrade to the Next Generation Very Large Array (ngVLA) will begin in late 2028 and early science operation will begin in mid 2031. This upgrade will replace the old antennae with more than 260 new antennae. These will be 18 meter in diameter and have three configurations: