Very Long Baseline Array

Eastern terminus of the VLBA, Saint Croix, U.S. Virgin Islands

The Very Long Baseline Array (VLBA) is a system of ten radio telescopes controlled remotely from the Array Operations Center in Socorro, New Mexico (USA) by the National Radio Astronomy Observatory. The array works together as the world's largest dedicated, full-time astronomical instrument using the technique of very long baseline interferometry. Its construction began in February 1986, and was completed in May 1993. The first observation using all ten sites occurred on May 29, 1993. The total construction cost was US$85 million.

Each VLBA station consists of an 82-foot (25 m) diameter dish antenna and an adjacent control building which houses the station computer, hard drives, and other equipment associated with collecting the radio signals gathered by the antenna. Each antenna weighs 218 tonnes (240 tons) and is nearly as tall as a ten story building when pointed straight up. The longest baseline in the array is 8,611 kilometres (5,351 mi).^[1]

The signals from each antenna are recorded on a bank of Terabyte hard drives and time stamped using atomic clocks. The drives are dispatched to the NRAO's Pete V. Domenici Science Operations Center in Socorro, New Mexico. There, they are combined using customized software in a digital correlator, a bank of 20, quad-core CPUs that also corrects for the rotation of the Earth, slight shifts in the Earth's crust, and timing differences.

VLBA Observations

The VLBA observes at wavelengths of 28 cm to 3 mm (1.2 GHz to 96 GHz) in eight discrete bands plus two narrow sub-gigahertz bands, including the primary spectral lines that produce high-brightness maser emission. The array can be scheduled dynamically, and its continuum sensitivity can be improved by a factor of 5 or more by adding the GBT and the phased VLA to the VLBA.

The VLBA radio telescopes are located at:

Hancock

North Liberty

Fort Davis

Los Alamos

Pie Town

Kitt Peak

Owens Valley

Brewster

Green Bank

VLA

VLBA locations (red) and HSA locations (blue) in contiguous United States

Four other sites are brought online for as much as 100 hours per four-month trimester. In this configuration, the entire array is known as the High-Sensitivity Array.^[2] These sites, with coordinates, are as follows:

St. Croix

Mauna Kea

Arecibo

Effelsberg

VLBA locations (red) and HSA locations (blue) around the world

Baseline distance and angular resolution

Distance between each VLBA baseline (km):^[3] The longest baseline in the array is 8,611 kilometres (5,351 mi).^[1]

Minimum angular resolution:

Wavelength (cm)	90	50	21	18	13	6	4	2	1	0.7
(mas)	22	12	5.0	4.3	3.2	1.4	0.85	0.47	0.32	0.17

See also

• List of radio telescopes

References

External links

• Official site