ALMA Strawperson Zoom - BnC Array Equivalent

Physical Descriptions:

  1. In moving from a C-array to a B-array configuration (a total of 32 antenna moves) we can move the first 18 telescopes to preferentially occupy the Northern and Southern pads to give an array suitable to observe Northern hemisphere of far South sources.

  2. Note we can move directly from C to BnC in a burst reconfiguration of the 18 antennas over one or two days or more gradually, moving 1-2 antennas per day. After finishing in BnC array we can then reconfigure the antennas for B array (12 antenna moves).




Antenna Positions:

Antenna positions are given here in meters in UVCON format . The X and Y positions are with respect to a reference position on the 5 degree mask. To convert to SAM56 coordintes:

SAM56 E = 628340 + X
SAM56 N = 7453250 + Y

Array Layout, UV Distribution (click for higher resolution) :



Antenna distribution superimposed onto terrain and the snapshot uv coverage for a transiting Dec +30 source.



Details of main lobe (click for higher resolution):



(Left Panel) Contour representation of the snaphsot main beam observing a dec=+30 source at transit. The fitted beam FWHM is 178 x 153 mas. At the 50% contour the ratio of NS to EW dimension is 1.15. (Right panel) Long track dirty beam for a dec=+30 sources observed +/-2hrs from transit. The fitted FWHM is 176 x 160mas. Note all antennas weights are assumed equal and image is naturally weighted. At the 50% contour the axial ratio is 1.10.



Beams, Snapshot and 4hr synthesis :



(Left panel) Snapshot dirty beam for Dec +30 source ovserved at transit. The plotted grayscale ranges between -5% and +10%. The fitted beam FWHM is 178x153 mas. (Right panel) Long track dirty beam for a dec=+30 sources observed +/-2hrs from transit. Note all antennas weights assumed equal and image is naturally weighted. The fitted beam FWHM is 176 x 160 mas.