[daip] [!5764]: aips - SNSMO with mode "VLMB" sometimes breaks the relationship between phase(per IF) and delay

[Eric Greisen]

Eric Greisen updated #5764
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                 Due: - Cleared - (was: 19 February 2015 05:28 PM)

SNSMO with mode "VLMB" sometimes breaks the relationship between phase(per IF) and delay
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           Ticket ID: 5764
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/5764
           Full Name: Michael Bietenholz
               Email: mbieten at yorku.ca
             Creator: User
          Department: AIPS Data Processing
       Staff (Owner): Eric Greisen
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: NRAO E2E
      Template Group: Default
             Created: 11 November 2014 03:35 PM
             Updated: 24 February 2015 05:20 PM
      Resolution Due: 24 November 2014 03:39 PM 



I have worked for a while with the code and now do not understand why
you are having a problem.  FRING makes the phase in a group of IFs =
phase of the first + a delay correction and stores that delay correction
in both the single-band and multi-band columns (APARM(5)=1 anyway).
SNSMO subtracts from the phase of each IF the smoothed delay contribution
averages the resulting phases, smooths the average, then restores the
smoothed multi-band delay.

I do not see how this can fail except when the smoothed MB delay is vastly
different from the unsmoothed.  In that case, the phase averaging could
produce odd results.

I think one thing to try would be to allow the IFs to be taken in groups 
(as we do for VLA), smooth only the phase of the lowest IF in the group
and then make the IF phase be that of the lowest corrected by the
SB delay (always same as MB in APARM(5)=1).

I may simply have to put such a thing back and then have you try it.

ERic Greisen




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