[daip] [Fwd: AD579_data reduction]

[Eric Greisen]

> From:
> Leonidas Dedes <ldedes at astro.uni-bonn.de>
>
> 
> I am currently reducing my data from day 1 of the project  AD579(L-band  
> 0.78mhz) and I am stuck with a problem during the calibration of the data.
> I am  using AIPS, following the standard procedure for spectral lines 
> given in the AIPS recipes.
> 
> After running the procedure VLACALIB in the initial CH0 file I find 
> closure errors in a numerous  baselines  far above 10%  even up to 
> 1000%(AD579_D1_C1)
> 
> To solve this, taking into account  the  aliasing problem, I  have 
> created a new CH0 file using only the upper part of the band. After  
> running the VLACALIB
> the closure errors remain again very high(AD579_D1_C2)
> 
> Next step was to  flag all the EVLA-EVLA baselines but it did not work 
> as the closure errors remain very high(AD579_D1_C3).
> Is there any additional solution to this problem? Should I flag the rest 
> of the erroneous baselines? Should I continue the calibration and just 
> apply self-calibration afterwards?
> 
> I have attached the 3 output files from the VLACALIB task.

Several comments:

1. Aliased data should be corrected for the aliasing before yo do any 
other calibration.  We have released a procedure FXALIAS which attempts 
to do this although we are re-examining it at present.  Then a new CH0 
file may be made with AVSPC.

2. At A array, 3C48 and 3C286 are not point sources.  You should use a 
model for each in the calibration.  Verb CALDIR and task CALRD are 
relevant here.

Eric Greisen