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

[Eric Greisen]

Eric Greisen updated #15791
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              Status: Closed (was: Open)

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): Eric Greisen
                Type: Issue
              Status: Closed
            Priority: Default
      Template group: Default
             Created: 26 February 2020 02:16 AM
             Updated: 28 February 2020 02:48 PM

15461. February 28, 2020 UVFIX EricThe differential aberration correction requires the comparisonof the apparent position of the source to the apparent positionof a point 10 asec North. Since we treat the apparent positionas fixed during the run (it actually isn't), we need to do thiscomparison only once at the same time that we compute thesource apparent position. In 31DEC18 and previous, this wasdone but only for the first source (with the result used forall sources). In 31DEC19 and 31DEC20, the comparison wasrecomputed every time a source changed which put a time changein the offset position but not the reference position. Thismade the correction a (false) function of time. Furthermore,when the input file was in B1950, the EPOCH variable did notstay at 2000 for this comparison. This could make the aberationcorrection a factor of ~200 rather than 0.99992! All these15461. February 28, 2020 UVFIX EricThe differential aberration correction requires the comparisonof the apparent position of the source to the apparent positionof a point 10 asec North. Since we treat the apparent positionas fixed during the run (it actually isn't), we need to do thiscomparison only once at the same time that we compute thesource apparent position. In 31DEC18 and previous, this wasdone but only for the first source (with the result used forall sources). In 31DEC19 and 31DEC20, the comparison wasrecomputed every time a source changed which put a time changein the offset position but not the reference position. Thismade the correction a (false) function of time. Furthermore,when the input file was in B1950, the EPOCH variable did notstay at 2000 for this comparison. This could make the aberationcorrection a factor of ~200 rather than 0.99992! All theseissues have been corrected with the aberation correction nowa function of source but not time (except for planets).Moved to 31DEC19 this date.

I don't know what your problem with calibration might be.  I made a mistake in running CLCAL that failed to calibrate 3C286 and the NGC source.  Fixing this I notice that the default phase type of phase cal is not very good.  A Self cal with a point model on the 3 calibrators made them very much better.  Even the NGC source got better with a solint of 1 minute.  I used 22 sec on the cals.
Ericissues have been corrected with the aberation correction nowa function of source but not time (except for planets).Moved to 31DEC19 this date.


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