[daip] problem with fring when including source structure

[Eric Greisen]

On 01/28/2015 05:14 AM, Juan-Carlos Algaba-Marcos wrote:
> Dear AIPS guru,
> I am trying to fringe fitting a uv dataset with a source model for phase
> reference methods. The source has actually been splited from the very
> same uvdata and imaged in difmap, The second fringe fitting is done
> using the CL table prior the initial fringe fitting.
> When I run FRING, I get the following error message:
>
> localh> FRING1: Task FRING  (release of 31DEC12) begins
> localh> FRING1: UVGET: doing no flagging this time
> localh> FRING1: Set integration time to  0.819200 seconds, hope that is ok
> localh> FRING1: Selecting and calibrating the data
> localh> FRING1: SETGDS: IMAGE    1 EPOCH 2000.0 UV EPOCH   -1.0
> localh> FRING1: USE UVFIX ON THE UV DATA OR EPOSW ON THE IMAGE
> localh> FRING1: Purports to die of UNNATURAL causes
>
> Apparently, uvdata and image do not have the same epoch. But if I look
> at their headers, it seems that the coordinate equinox is the same (J2000):
>
>  >imh
> AIPS 1: Image=MULTI     (UV)         Filename=IMOGABA9F043.UVDATA.   1
> AIPS 1: Telescope=VLBA               Receiver=VLBA
> AIPS 1: Observer=N13SL01             User #=  251
> AIPS 1: Observ. date=19-NOV-2013     Map date=26-JAN-2015
> AIPS 1: # visibilities    249176     Sort order  TB
> AIPS 1: Rand axes: UU-L-SIN  VV-L-SIN  WW-L-SIN  TIME1  BASELINE
> AIPS 1:            SOURCE  FREQSEL  INTTIM  GATEID  CORR-ID
> AIPS 1: ----------------------------------------------------------------
> AIPS 1: Type    Pixels   Coord value     at Pixel     Coord incr   Rotat
> AIPS 1: COMPLEX      3   1.0000000E+00       1.00  1.0000000E+00    0.00
> AIPS 1: STOKES       1  -2.0000000E+00       1.00 -1.0000000E+00    0.00
> AIPS 1: FREQ       256   4.3400000E+10       0.52  6.2500000E+04    0.00
> AIPS 1: IF           4   1.0000000E+00       1.00  1.0000000E+00    0.00
> AIPS 1: RA           1    00 00 00.000       1.00       0.000000    0.00
> AIPS 1: DEC          1    00 00 00.000       1.00       0.000000    0.00
> AIPS 1: ----------------------------------------------------------------
> AIPS 1: Coordinate equinox 2000.00
> AIPS 1: Maximum version number of extension files of type FQ is   1
> AIPS 1: Maximum version number of extension files of type NX is   1
> AIPS 1: Maximum version number of extension files of type HI is   1
> AIPS 1: Maximum version number of extension files of type AT is   1
> AIPS 1: Maximum version number of extension files of type CT is   1
> AIPS 1: Maximum version number of extension files of type AN is   1
> AIPS 1: Maximum version number of extension files of type BP is   1
> AIPS 1: Maximum version number of extension files of type CL is   5
> AIPS 1: Maximum version number of extension files of type CQ is   1
> AIPS 1: Maximum version number of extension files of type GC is   1
> AIPS 1: Maximum version number of extension files of type IM is   1
> AIPS 1: Maximum version number of extension files of type MC is   1
> AIPS 1: Maximum version number of extension files of type SN is   4
> AIPS 1: Maximum version number of extension files of type SU is   1
> AIPS 1: Maximum version number of extension files of type TY is   1
> AIPS 1: Keyword = 'OLDRFQ  '  value =  2.17000000D+10
>  >
>  >im2h
> AIPS 1: Header for second input image or data set
> AIPS 1: Image=0827+243  (MA)         Filename=0827+243    .ICC043.   1
> AIPS 1: Telescope=VLBA               Receiver=VLBA
> AIPS 1: Observer=N13SL01             User #=  251
> AIPS 1: Observ. date=19-NOV-2013     Map date=28-JAN-2015
> AIPS 1: Minimum=-1.19117908E-02      Maximum= 7.42246687E-01 JY/BEAM
> AIPS 1: ----------------------------------------------------------------
> AIPS 1: Type    Pixels   Coord value     at Pixel     Coord incr   Rotat
> AIPS 1: RA---SIN   512    08 33 49.342     256.00      -0.000250    0.00
> AIPS 1: DEC--SIN   512    24 00 41.714     257.00       0.000250   -0.24
> AIPS 1: FREQ         1   4.3432000E+10       1.00  6.4000000E+07    0.00
> AIPS 1: STOKES       1  -2.0000000E+00       1.00  1.0000000E+00    0.00
> AIPS 1: ----------------------------------------------------------------
> AIPS 1: Coordinate equinox 2000.00
> AIPS 1: Map type=NORMAL              Number of iterations=       1
> AIPS 1: Conv size= 0.00473 X 0.00162   Position angle=  58.26
> AIPS 1: Maximum version number of extension files of type HI is   1
> AIPS 1: Maximum version number of extension files of type CC is   1
>  >
>
> In any case, I have tried the suggestion and I have run EPOSW a couple
> of times on the image (to get B1950 and get back J2000). I still get the
> same error message. Alternatively, I copied the uvdata and run UVFIX on
> it, this time being able to run FRING, giving very poor solution results
> (>60% solution failed), whereas simple fringe fitting without including
> the source structure finds almost all solutions.
>
> This leads me to think that the coordinates are not properly set-up in
> either the uvdata or the image. But this is quite puzzling, as image has
> been done from the dataset and, if one coordinate shall be wrong, so the
> other too.
>
> Below are the inputs for FRING. I have tried this with a couple of
> (point-like) sources, either including clean components or gaussian fit
> as model in the image CC table. My version of AIPS is 31DEC12. Do you
> have any suggestions about this issue?

Use PRTAB on the source table.  Column 13 has an EPOCH - check those 
values.  If they are -1 change them with TABPUT.  Discard the UVFIX file 
and use the EPOSW version with 2000 in the header.

If this is not the source of the problem, let me know...

Eric Greisen