[daip] AIPS, PCAL and CHKFC troubles...

[Eric Greisen]

jsf31 at mrao.cam.ac.uk wrote:
> Dear Eric Greisen,
> 
> I am having trouble with a couple of AIPS tasks and am unsure whether 
> this is the way I am using them or perhaps a problem within the tasks 
> themselves.
> 
> I am attempting to complete a polarisation calibration on an 
> interferometer with fairly bad instrumental polarisation (~10-50% 
> leakage), where the calibrators are all partially resolved. As PCAL 
> makes the assumption that the Stokes Q and U images are a scaled version 
> of the Stokes I image, I am having to try a "polarisation 
> self-calibration", calculating the instrumental polarisation initially 
> using SOLTYPE 'ORI-' then iteratively imaging and deconvolving in order 
> to develop a model to feed into PCAL. Unfortunately, PCAL seems to 
> either crash or never converges when attempting to do this, and I 
> noticed that Martin Hardcastle seems to have had a similar problem back 
> in 2005:
> 
> http://listmgr.cv.nrao.edu/pipermail/daip/2005-December/009065.html
> 
> My ignorance of what PCAL is actually doing in the code certainly does 
> not help, but I am starting to suspect that the problem may well be with 
> the task itself. Using SOLTYPE 'RAPR' does appear to calculate the 
> leakage terms in a reasonable way although I am cautious about this, as 
> I believe the linear model is only designed to deal with small 
> instrumental polarisation. May it please be possible to confirm whether 
> this is a problem with PCAL or otherwise, and if so is there any hope 
> that PCAL may be fixed in the future?
> 
> Additionally, I am also having trouble with CHKFC when attempting to 
> check the sky has been sufficiently covered with clean boxes when 
> splitting into 31 facets. The boxfile has been made with SETFC and the 
> first two facets are defined in the boxfile as:
> 
> C     1  1012  1012   03 33 36.40  -36 08 25.0
> 00001  -1    507    512    513
> C     2  1012  1012   03 33 36.40  -36 25 47.3
> 00002  -1    507    512    513
> 
> I then run CHKFC with the following parameters:
> 
> AIPS 2: CHKFC:  Makes images showing the fields and boxes in BOXFILE
> AIPS 2: Adverbs     Values                 Comments
> AIPS 2: ----------------------------------------------------------------
> AIPS 2: OUTNAME    'CHECK'                 Output Image name (name)
> AIPS 2: OUTSEQ        1                    Output Image name (seq. #)
> AIPS 2: OUTDISK       3                    Disk drive #
> AIPS 2: BOXFILE    '/home/jsf31/boxfile.tx disk file to read field locs
> AIPS 2:            t'
> AIPS 2:                                    and Clean boxes
> AIPS 2: COORDINA   *all 0                  Center RA, Dec
> AIPS 2: CELLSIZE      1.2         1.2      (X,Y) size of grid in asec
> AIPS 2: IMSIZE     1024        1024        field size
> AIPS 2: NFIELD       31                    Number facets
> AIPS 2: RASHIFT    *all 0                  New facet RA shift (asec)
> AIPS 2: DECSHIFT   *all 0                  New facet Dec shift (asec)
> AIPS 2: NBOXES       31                    Number Clean boxes
> AIPS 2: CLBOX      *all 0                  Clean boxes: facet #1
> AIPS 2: DOBLANK       0                    > 0 Use blanks for unCleaned
> AIPS 2: DOWEDGE      -1                    > 0 Add field number in boxes
> 
> and the output is:
> 
> CHKFC2: ZABORS: signal 8 received
> MRAOSW> CHKFC2: ABORT!
> 
> Again, I am totally unsure if this is the task or me, but I have checked 
> and double checked and tried various variations of the parameters but it 
> seems to crash everytime - although using the boxfile in IMAGR appears 
> to work fine.
> 
> I would be exceptionally grateful for any help you may be able to 
> provide, and please accept my apologies for having written you an essay!
> 
> Kind Regards
> Jamie Farnes

Can you send me your boxfile for the CHKFC problem.  I tried with my 
latest boxfile and alll was lovely on gnu and Intel LNX64 versions.
What is your OS?

Eric Greisen