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| NRAO Home > VLA > Array Configurations | ||
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VLA Configurations and Proposal Deadlines
The antennas in the Very Large Array are used like the zoom lens in
a camera. When they are in the A configuration, the telescopes extend
over the 21 kilometer (13 mile) length of each arm. This simulates
a single dish that is 36 kilometers (22 miles) in diameter. In this
configuration, we have the most magnification and can see the greatest
detail. The size of the array gradually decreases with the B and C
configurations until, in the D configuration, the telescopes are all
placed within .6 kilometer (.4 mile) of the center. In the smaller
configurations, scientists can study the overall structure of the source
they are observing. By observing the same source in each configuration,
scientists can gather a great deal more information.
The telescopes are moved about every four months. The
configurations listed below with a lower-case "n", such as "DnC" and "BnA"
are hybrid configurations in which the antennas on the east and west
arms are moved in for the next configuration, but those on the north
arm remain extended for a short time to enhance our view of sources in
the southern sky near the galactic center.
(dates are approximate!)
The NRAO is currently considering a plan to reverse the order of the
configuration cycles of the VLA/EVLA from the long-used D-> A-> B->
C-> D to D-> C-> B-> A-> D, beginning with the D configuration at the
end of 2009, to facilitate correlator commissioning and early science
with the EVLA. No decision has been taken. We will keep the
community informed.
For more information on the VLA, see "An Overview of the VLA" in the Observational Status Summary.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc.
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