[daip] [!12546]: AIPS - Don't understand CLCAL interpolation

[Michael Bietenholz]

              Status: Open (was: Closed)

Don't understand CLCAL interpolation
------------------------------------

           Ticket ID: 12546
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/12546
                Name: Michael Bietenholz
       Email address: 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: 08 August 2018 07:45 PM
             Updated: 09 August 2018 03:44 PM
           Reply due: 13 August 2018 03:45 PM (4d 0h 0m)
      Resolution due: 05 May 2021 12:00 AM (999d 8h 15m)

Hi Eric:

  As you say, I would have indeed expected phase vs time to be
quadratic, but its not - e.g. for antenna FD, there are two local
maxima (~12:15 and 12:40), so its dong something more complicated.
The interpolation for HN also seems very wierd.  'CUBE' *does* produce
nice quadratic-looking phase-vs-time plots for all ants including HN

(I agree with you about rates & VLA - the few times I've tried in
desperation to solve for rates for VLA data, its never bought me
anything.  This data, however, is VLBA.  Even here, I'm not sure rates
will buy me anything - I'm not sure that the residual rates on the
calibrator sources tell you anything useful about the rates in the
interval in between, so this may all be pointless for this particular
run.  Nonentheless, I'd like to understand what is happening - in VLBI
often one has no choice but to solve for the rates)

              michael




On Thu, 9 Aug 2018, Eric Greisen wrote:

> If the rate of change of delay is linear from time A to B
> then the delay will be quadratic from A to B as will be
> the phase.  This explains large parts of the plots you
> sent.
> 
> I encourage VLA users not to solve for rate because
> it has an enormous influence on delay and phase.
> 
> Eric Greisen
> 
> 
> Ticket Details
> 
> 

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