[daip] [!4237]: aips - PCAL only correcting one IF

[Andy Biggs]

Andy Biggs updated #4237
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PCAL only correcting one IF
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           Ticket ID: 4237
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/4237
           Full Name: Andy Biggs
               Email: abiggs at eso.org
             Creator: User
          Department: AIPS Data Processing
       Staff (Owner): -- Unassigned --
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: ALMA E2E
      Template Group: Default
             Created: 13 January 2014 02:29 PM
             Updated: 13 January 2014 02:29 PM
                 Due: 15 January 2014 02:29 PM (2d 0h 0m)
      Resolution Due: 22 January 2014 02:29 PM (9d 0h 0m)



Hi. I have some old data that were once processed using AIPS 31DEC06. I want to play around with the calibration and so I UVCOP the existing file to a new one (don't want to mess with the original) in 31DEC14. If I run PCAL on the new file (using the single scan of unpolarized 3C84) it seems to run fine and the messages show reasonable corrections for *both* IFs. If I then try to plot Stokes Q in UVPLT, the first IF is corrected, but the second IF is not. If I then look at the AN table, the reason for this is apparent - there are only entries for IF1. After the UVCOP but before PCAL, there were entries for both (taken from a PCAL run many years ago):

Old:

Ant   1 = VLA: N48 BX=    -5271.2645 BY=     -823.5765 BZ=     7791.9847
Mount=ALAZ  Axis offset=  0.0058 meters    IFA               IFB
Feed polarization type =                    R                 L
Lin. approx. IF(  1) as amp, phase =  0.0883,  -89.9    0.0842,  -84.6
Lin. approx. IF(  2) as amp, phase =  0.0807,  -95.3    0.0910,  -77.6

Ant   2 = VLA: W24 BX=     1005.4478 BY=    -2643.0110 BZ=    -1472.1587
Mount=ALAZ  Axis offset=  0.0009 meters    IFA               IFB
Feed polarization type =                    R                 L
Lin. approx. IF(  1) as amp, phase =  0.1094,  -84.1    0.0181, -118.0
Lin. approx. IF(  2) as amp, phase =  0.1178,  -82.6    0.0275, -107.3

New:
Ant   1 = VLA: N48 BX=    -5271.2645 BY=     -823.5765 BZ=     7791.9847
Mount=ALAZ  Axis offset=  0.0058 meters    IFA               IFB
Feed polarization type =                    R                 L
Lin. approx. IF(  1) as amp, phase =  0.0878,   32.8    0.0836,  152.7

Ant   2 = VLA: W24 BX=     1005.4478 BY=    -2643.0110 BZ=    -1472.1587
Mount=ALAZ  Axis offset=  0.0009 meters    IFA               IFB
Feed polarization type =                    R                 L
Lin. approx. IF(  1) as amp, phase =  0.1089,   38.7    0.0180,  119.4

Copying the data using FUDGE does not encounter this problem - PCAL corrects both IFs in UVPLT and entries for both are in the AN file:

Ant   1 = VLA: N48 BX=    -5271.2645 BY=     -823.5765 BZ=     7791.9847
Mount=ALAZ  Axis offset=  0.0058 meters    IFA               IFB
Feed polarization type =                    R                 L
Lin. approx. IF(  1) as amp, phase =  0.0878,   32.8    0.0836,  152.7
Lin. approx. IF(  2) as amp, phase =  0.0803,   55.9    0.0904,  131.1

It seems therefore that I can progress by "fudging" the issue. However, I thought I'd pass this finding on to you in case you'd like to investigate. Data can be easily made available if desired.

Andy


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