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What are the Angles Separating the Tracks of the VLA Antenna Layout and What is its Orientation Relative to Geographic North?

-- Peter | July 3, 2024

Question:

Hi there, I have a simple question that I can’t find anywhere: What are angles of the 3 tracks at the VLA, and if you can answer that, are they based on magnetic or true north?

Regards
Peter

-- Peter

Answer:

The angles which separate the arms of the “Y” configuration of the VLA antennas are 120 degrees. Additionally, according to Barry Clark, NRAO Astronomer in Socorro New Mexico, there are two other less-well-known features of the VLA Y-configuration. The first is that the “Y” is rotated by about 5 degrees relative to geographic north, done to allow for the array to measure objects slightly differently (specifically, slightly different (u,v) coverage) when observing in the east as opposed to the west (and vise-versa). The second tidbit is that the north arm of the VLA is about 1 kilometer shorter than the east and west arms due to a land acquisition issue when the VLA was built.

-- Jeff Mangum

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