[daip] [!6280]: AIPS - Dispersive delay fitting in AIPS

[Adam Deller]

Adam Deller updated #6280
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Dispersive delay fitting in AIPS
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           Ticket ID: 6280
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/6280



Hi Eric,

Sorry I haven't gotten you that test dataset yet - still working on it.  Early next week hopefully.

In general, I think we do want to be able to solve for calibrators in a multisource file and apply to targets.  For the LOFAR case, though, working with single source files is probably fine because scans end up in separate files anyway.

In terms of the zenith angle dependence of the dispersive delay, in principle one would have already applied TECOR before running this task, hence the bulk (zenith angle dependent) ionospheric delay should already have been removed, and what we are solving for is the residual.  That residual might be positive or negative, so I don't think we would want to extrapolate it with zenith angle directly.  Just applying it simply, like we do with regular calibration, is the easiest starting point and I would be happy to start with this.  A more complicated but potentially better approach would be to add  the solution to the existing, already-applied dispersive delay value and basically recalculate the TECOR correction.  (Of course, eventually you would really like to have multiple calibrators at once and fit a plane and use that to interpolate/extrapolate directly to the position of the target, but let's crawl before we sprint.)

Great to hear that you've already made a lot of progress with KRING.  I think it is important to be able to use a full global fit, so if KRING is currently using baselines to the reference antenna only, then obviously we would really like to extend that.  But of course just getting the infrastructure in place to deal with the solutions is important and a big step too.

Cheers,
Adam

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