[daip] CLCOR position shifting question

[Leonia Kogan]

Mark,

You can argue my previous message argument about the instrumental delay,
considering your data have zeros for those delays.

Even in this case:
CLCOR calculates the phase correction for  each IFs as production of the 
calculated delay and the frequency difference relatively the first IF.
1as position shift is large enough to create many turns of phase between
the neighbor IFs especially for VLBI (is it VLBI?). CLCOR brashes aside 
the integer turns of phase! Therefore the multi band delay (MOD 
deltaphi/deltaf, 1) can be smaller than expected.

So you can try your test with much much smaller source shift.

Leonia
Mark Reid wrote:
> Leonia,
> 
>    I have a question about CLCOR and shifting source positions.
> I am writing a program to take multi-band delays and rates and solve for 
> source position offsets.
> 
> For a quick check on my code I took some well calibrated data (meaning 
> the multi-band delays and rates are near zero) and shifted the positions 
> of some sources by about 1 arcsecond (with CLCOR/ANTC).   Then I reFRING 
> to get new multi-band delays and rates.
> 
> When I fit the new delays and rates for source position shifts, I find 
> it works for the rates, but not for the multi-band delays. Specifically, 
> it looks like the multi-band delays are pretty small.
> 
> So, the question: does CLCOR/ANTC put in frequency dependent phase 
> shifts that would correspond to the desired changes in multi-band delays 
> when one shifts source positions?
> 
> Thanks,
> Mark
> 
> PS: regarding the ionospheric code you put into CLCOR a while ago, we 
> haven't forgotten about it.  We've been temporally sidetracked getting 
> our huge VLBA project started.  However, a postdoc in China and I are 
> just getting back to testing it.
> 
> 
> 
> -------------------------------------------------------------
> Mark J. Reid                 Phone: 617-495-7470
> Harvard-Smithsonian CfA      Fax  : 617-495-7345
> 60 Garden Street             Email: reid at cfa.harvard.edu
> Cambridge, MA 02138, USA     Web  : www.cfa.harvard.edu/~reid
> -------------------------------------------------------------