[daip] help with UVLSF, please

[Claire Chandler]

We can't run UVLSF on the calibrator because we have no way of removing a 
scaled version of it from the target source.  Such a program could be 
written, and it is the equivalent of a frequency-dependent BLCAL.  But 
even then we would have to worry about the fact that there is no aliasing 
in the line emission, so such a correction would not be valid for the line 
data.

Claire

On Wed, 12 Dec 2007, Gustaaf van Moorsel wrote:

> On 11 Dec 2007, at 22:12, Eric Greisen wrote:
>
>>> UVLSF with high order will only work if there is really a significant
>>> continuum signal and you can use e.g at least half the channels in the
>>> fit.  In particular, the lower numbered channels need to be line
>>> free.
>
> It seems to me that Elias' data suffered from a lack of continuum,
> not so much a lack of channels at each end.
>
> If that is the case, and the aliasing is not very time variable,
> as my tests suggest, couldn't we do the UVLSF fit on the bandpass
> calibrator (or maybe even better, the phase calibrator) only?
> Surely in those cases the continuum is strong enough for UVLSF to
> work reliably.  That will give us the correct functional form of
> the aliasing for each baseline.  We can then use this functional
> form for the source data, which then only need to be scaled,
> thereby reducing the number of free parameters from 4 to 1.
>
> I don't know how feasible it is to implement such a thing; for now
> I'd like to hear if you think this is an approach that might work.
> For instance, is the shape of the aliasing on a calibrator trans-
> ferrable to the source?
>
> Gustaaf
>
>
>