[daip] TY table problem

[Craig Walker]

It is possible that this is a calibration transfer issue, but I'm not
sure who should get that.

My TY table after calibration transfer, and running VLBAPIPE which
merges the tables, has some entries that are exact duplicates in every
parameter except source number.  They occur at the ends of a few scans
at a few stations.  These entries mess up APCAL and lead to SN, and
CL tables that do not cover the end of the scan (2 entries missing 
for affected stations in a CL table with 30 second intervals.  That in turn 
causes calibration application to get messed up for the last minute of the
scan.  I spotted the problem because I get full phase winds at 
some stations over 1 minute at the end of a couple of scans at a 
few stations after application of TECOR.  The CL table after TECOR
does not have any entries that justify such a wind, but it does 
not have entries for the tail of the scan.  I suspect the calibration
application is interpolating to the next scan which is in a very different
direction on the sky.

Here is a sample PRTAB output for the offending TY table (note the entries
at 08:03:48.5):

 eolus     PRTAB(31DEC02)   2263     26-OCT-2002  15:48:20    Page   14
     ROW   TIME         TIME INTER   SOURCE ID   ANTENNA    SUBARRAY   FREQ ID   TSYS 1      TANT 1      TSYS 2      TANT 2
    1165   08:00:07.5   00:02:00.0       3           4          1         1      2.260E+01     INDE      2.293E+01     INDE
    1165                                                                         2.523E+01     INDE      2.405E+01     INDE
    1166   08:02:11.0   00:01:53.0       3           4          1         1      2.255E+01     INDE      2.292E+01     INDE
    1166                                                                         2.516E+01     INDE      2.407E+01     INDE
    1167   08:03:48.5   00:01:22.0       3           4          1         1      2.250E+01     INDE      2.290E+01     INDE
    1167                                                                         2.512E+01     INDE      2.399E+01     INDE
    1168   08:03:48.5   00:01:22.0       1           4          1         1      2.250E+01     INDE      2.290E+01     INDE
    1168                                                                         2.512E+01     INDE      2.399E+01     INDE
    1169   08:06:54.5   00:01:54.0       1           4          1         1      2.335E+01     INDE      2.359E+01     INDE
    1169                                                                         2.594E+01     INDE      2.475E+01     INDE
    1170   08:08:51.5   00:02:00.0       1           4          1         1      2.342E+01     INDE      2.368E+01     INDE
    1170                                                                         2.597E+01     INDE      2.476E+01     INDE

There is no apparent problem in the bw051bcal.vlba file from tsm 
(calibration data file generated for the pre-calibration transfer
calibration scheme).  There are no duplicate entries or anything of 
the sort.  

I will now either have to edit the data, or the TY table.  I think I
will do the TY table, eliminating the values.  I have put the
original TY table and all processing tables created by the most
recent VLBAPIPE run (before editing) on eolus in 
>uc
AIPS 1: Catalog on disk  2
AIPS 1:  Cat Usid Mapname      Class   Seq  Pt     Last access      Stat
AIPS 1:   36 2263 BW051B      .TASAV .    1 UV 26-OCT-2002 16:02:05

I have hardcopy plots of phases which show what happened.

I see two problems to address:
  1.  The TY table shouldn't have the duplicate entries.
  2.  The calibration application shouldn't interpolate across scan
      boundaries to CL points deep in the scan (if that is what 
      happened).  This might best be handled by always ensuring that
      there is are CL entries at the ends of each scan, even if they
      have to be created by some sort of extrapolation.


Craig


---------------------------------------------------------------------
    R. Craig Walker            Array Operations Center
    cwalker at nrao.edu           National Radio Astronomy Observatory
    Phone  505 835 7247        P. O. Box O
    Fax    505 835 7027        Socorro NM 87801   USA
---------------------------------------------------------------------