Subarrays

by Stephan W. Witz last modified Jul 06, 2012 by Stephan Witz

The separation of the VLA into up to three subarrays will be supported for general observing in semester 2013A,  Each subarray is independent for the entire duration of an observation, and is set up using an independent scheduling block (SB).  All SBs must be the same length, and will be scheduled simultaneously.  The antennas comprising each subarray will remain in the same subarray for the duration of the observation.  There are some limitations on the number of antennas that can comprise each subarray, due to the architecture of the correlator.  The correlator operates on 8 groups of 4 antennas (up to 32 antennas total), and each group can only contain antennas from one subarray.  Thus, for three subarrays and 27 antennas, antennas may be distributed as 8, 9, 10 antennas, or 11, 11, 5 antennas, but not 9, 9, 9 antennas since each subarray of 9 antennas requires 3 groups, and the three subarrays together would require 3x3=9 groups, where only eight are available.  For two subarrays the grouping requirement gives no restrictions, and the antennas may be flexibly allocated between the two subarrays.

Subarrays will only be available for general observing with the 8-bit samplers and 2 GHz bandwidth.  Access to the 3-bit samplers and/or more flexible correlator set-ups will be offered under the shared risk observing programs.