[daip] [!4536]: AIPS - SNSMO in VLMB mode sometimes breaks the relationship between phase(per IF) and delay

[Michael Bietenholz]

Michael Bietenholz updated #4536
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SNSMO in VLMB mode sometimes breaks the relationship between phase(per IF) and delay
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           Ticket ID: 4536
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/4536
           Full Name: Michael Bietenholz
               Email: mbieten at yorku.ca
             Creator: User
          Department: AIPS Data Reduction
       Staff (Owner): Eric Greisen
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: NRAO E2E
      Template Group: Default
             Created: 19 February 2014 06:58 PM
             Updated: 02 November 2015 07:39 AM
      Resolution Due: 10 November 2015 12:00 AM (7d 16h 20m)



Sorry Eric - I forgot we had to specify NPIECE.  SNSMO does indeed maintain the coherence across the IFs with NPIECE set correctly.

It can still break the R-L coherence.  However, I thought about this and realized that its inevitable in the case of noisy solutions:  it can happen that in R you're interpolating over a phase jump of +179degs between scans, while in L its -179degs.  R and L are actually well coherent (within 2degs), but the phase will be interpolated in the opposite direction.  This isn't great if you want to form Stokes I of course.

Subsequent phase-cal with separate solutions for R and L could fix it.

In principle one could make SNSMO resolve phase ambiguities the same way in both R+L.  That would be better in my particular case - I'm not sure if its the thing to do in general though.  If R+L are in fact totally independent that you *want* to resolve the ambiguities independently.

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