[daip] [!15791]: AIPS - problems with 31DEC19 AIPS version

Wed Feb 26 04:16:56 EST 2020

Cristina Romero-Canizales updated #15791
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problems with 31DEC19 AIPS version
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           Ticket ID: 15791
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/15791
                Name: Cristina Romero-Canizales
       Email address: cristina.rocc at gmail.com
             Creator: User
          Department: AIPS Data Reduction
       Staff (Owner): -- Unassigned --
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: NRAO E2E
      Template group: Default
             Created: 26 February 2020 09:16 AM
             Updated: 26 February 2020 09:16 AM
           Reply due: 28 February 2020 09:16 AM (2d 0h 0m)
      Resolution due: 22 November 2022 12:00 AM (999d 14h 44m)

Hi,I've experienced calibration and imaging problems in AIPS version 31DEC19. I made several tests using another computer, as well as using an older AIPS version. I describe the problem and the tests made in the following lines. Hopefully this helps you to find out what is wrong with AIPS 31DEC19 version.Cheers,Cristina.
-------VLA project AB618 (29-NOV-1992) includes C-band observations of NGC3393 in A-configuration. I reduced this same data-set back in 2013 using AIPS version 31DEC12. While preparing an AIPS tutorial, I re-reduced this data-set again using version 31DEC19. When imaging, I used a cellsize=0.06 arcsec. IMAGR complained with the following warning:--------------------------------------------------------------------------------ABJ   > IMAGR1: **** WARNING data discarded outside usable part of UV plane ****ABJ   > IMAGR1: **** Actual Umax 1.2875E+08 exceeds limit 1.2009E+06        ****ABJ   > IMAGR1: **** Use cellsize <   0.00056 not   0.06000 to get all data ****ABJ   > IMAGR1: **** using a U guard band of  0.300 of a radius             ****ABJ   > IMAGR1: **** Actual Vmax 7.8450E+07 exceeds limit 1.2009E+06        ****ABJ   > IMAGR1: **** Use cellsize <   0.00092 not   0.06000 to get all data ****ABJ   > IMAGR1: **** using a V guard band of  0.300 of a radius             ****ABJ   > IMAGR1: **** WARNING data included out of inner portion of UV plane ****ABJ   > IMAGR1: **** Watch for high-frequency & other poor cleaning effects ****--------------------------------------------------------------------------------I then used a cellsize of 0.0005 arcsec, which would be ok if these were VLBI data. To my surprise, IMAGR worked just fine with the new cellsize. I loaded in AIPS the SPLIT file that I had kept from my old data reduction and attempted to make an image using cellsi=0.06. IMAGR didn't show the warning but received an abort signal (IMAGR1: ZABORS: signal 11 received). I repeated all this in another computer running 31DEC19 version and reproduced the same problems. I also note that I ran midnight job to get the most recent updates in the 2019 version and re-did all the calibration and imaging and the problems persisted.To investigate what was going on, I ran UVPRM on both the old and the new SPLIT files and this is the difference I see:------------------------------------------------------ SPLIT file obtained in 31DEC19:AIPS 1: Keyword = 'UVPRAMIN'  value =  9.035373E+05AIPS 1: Keyword = 'UVPRAMAX'  value =  1.294114E+08------------------------------------------------------ SPLIT file obtained in 31DEC12:AIPS 1: Keyword = 'UVPRAMIN'  value =  4.138921E+03AIPS 1: Keyword = 'UVPRAMAX'  value =  5.928382E+05------------------------------------------------------ The SPLIT file obtained in 31DEC19 clearly shows uv limits similar to those expected from a VLBI experiment. The AN files don't seem to differ between the old and the new SPLIT files.I made a SPLIT file also with DOCAL=-1 to check if somehow the calibration had messed up the uv limits. But the headers after running UVPRM are consistent.In addition, another (rather worrisome) thing to note is that when checking the calibration with LISTR opty 'matx', the phase calibrator looks just fine, but the flux calibrator displays very large phases, with Ampscalar average of matrix = 1.562E+02( 1.759E+00) sigma = 4.609E+01 in IF1, and Ampscalar average of matrix = 1.517E+02( 1.760E+00) sigma = 4.614E+01 in IF2. It doesn't matter if when running SETJY I use new (2017) or old (1995.2) values with APARM. In contrast, in the old data reduction made in 31DEC12 the phases were very close to zero: Ampscalar average of matrix    =-3.626E-02( 2.091E-01) sigma = 4.913E+00 in IF1 and Ampscalar average of matrix =-1.885E-02( 2.067E-01) sigma = 4.858E+00 in IF2.I repeated all the above using AIPS 31DEC17 version. For the flux calibrator (3C286) and using exactly the same parameters in CALIB, I obtain same number of good solutions, but the average closure rms is different:------------------------------------------------------Average closure rms =  0.00106 +- 0.00003  (in 31DEC17)Average closure rms =  0.00322 +- 0.00009  (in 31DEC19)------------------------------------------------------For the phase calibrator (1034-293) I obtain same number of good solutions and the same average closure rms in both 2017 and 2019 versions. The 2017 solutions are in fact the same as I had recorded in my log of data reduction using 31DEC12. After running CLCAL, I checked again the calibration using LISTR opty 'matx'. In contrast with the data reduction made in 31DEC19, this time in 31DEC17 the phases of the flux calibrator are closer to zero: Ampscalar average of matrix    =-7.542E-02( 2.068E-01) sigma = 4.859E+00 for IF1, and Ampscalar average of matrix    =-6.981E-02( 2.046E-01) sigma = 4.807E+00 for IF2. Then, running SPLIT, UVPRM in the SPLIT file for my target and the IMAGR, I obtained similar results to when I did all this in AIPS version 31DEC12. IMAGR didn't failed and gave a reasonable beam size and UVPRM also gave reasonable uv limits.Just as an extra (and random) check, I run UVPRM on a SPLIT file from an EVN observation. The result is that UVPRM from 31DEC19 was unable to show uv limits. The reason was: UVPRM: FOUND    0 POINTS: NOT ENOUGH TO SELF-SCALE.


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