As of Mon Jul 15 11:22:42 2024

VLBAPCOR: Procedure to correct instrumental phases


INNAME                             Input UV file name (name)
INCLASS                            Input UV file name (class)
INSEQ             0.0     9999.0   Input UV file name (seq. #)
INDISK            0.0        9.0   Input UV file disk unit #
TIMERANG                           Time range of a calibrator
                                    1-4 = start day,hr,min,sec
                                    5-8 = end   day,hr,min,sec
                                   MUST BE SPECIFIED
REFANT             0.0      20.0   Ref. antenna, 0=>the first
SUBARRAY           0.0    9999.0   Subarray;  0 => all.
CALSOUR                            Calibrator source name;
                                   blank => any
GAINUSE                            CL table to use; 0=>highest
                                   ADVERBS FOR ANTENNAS NOT
                                   CONTAINED IN PC TABLE:
INVERS            -1.0   46655.0   Input  PC table, 0=>last one
OPCODE                             'CALP' if you are missing PC
                                   information for any antenna;
                                   otherwise ' '
ANTENNAS                           antennas for which manual
                                   phase corrections should be
                                   obtained (i.e. they are
                                   missing from the PC table or
                                   are the pcals in PC table are
CHINC                        1.0   Channel increment in FRING
                                   < 0 -> find from data


Type: Procedure
Use:  VLBAPCOR is a procedure that creates a CL table which
      corrects the instrumental phases and delays using the
      pulse-calibration information in the PC table and
      will run FRING for any antennas which are not in
      the PC table if instructed to do so.  This should
      be run after VLBACALA (or VLBAPANG for polarization
      experiments) but before VLBAFRNG/VLBAKRNG.
      Type RUN VLBAUTIL to make the VLBAPCOR procedure

  INNAME.....Input UV file name (name).      Standard defaults.
  INCLASS....Input UV file name (class).     Standard defaults.
  INSEQ......Input UV file name (seq. #).    0 => highest.
  INDISK.....Disk drive # of input UV file.  0 => any.
  TIMERANG...Time range of the calibrator to be used. In order:
             Start day, hour, min. sec,
             End day, hour, min. sec. Days relative to
             reference date.
             MUST BE SPECIFIED.  Pick a scan on a calibrator where
             all antennas are present and have strong fringes.
  REFANT.....Reference antenna, 0 => the first in the antenna list
             Set to a stable antenna that is preferably in the entire
  SUBARRAY...The subarray to use. 0 => all
  CALSOUR....Calibrator source name.
  GAINUSE....Number of CL table with all calibration up to this point.
             0 => highest
  OPCODE.....OPCODE in CLCAL; use 'CALP' if you have antennas
             with no entries in the PC table, otherwise use default.
             If OPCODE is set to 'CALP' and ANTENNAS are set then
             additional steps are added to the procedure to find the
             instrumental phase corrections for antennas that are not
             in PC table.  If OPCODE='CALP but ANTENNAS are not set
             then the phase corrections are not solved for and the
             antennas which are not in the PC table will be uncorrected
             in the resulting CL table.  See EXPLAIN file for a
             detailed explanation of how to deal with ANTENNAS which
             are not in the PC table after VLBAPCOR.
  ANTENNAS...Antennas that are not in the PC table, a manual
             instrumental phase correction will be found for these
             using FRING.  This FRING will be run on the scan that is
             selected in TIMERANGE, therefore make sure that the
             segment of data in the TIMERANGE has strong fringes on
             all antennas that the instrumental phase correction is
             desired.  OPCODE must be set to 'CALP' for this option.
             0=> do not find manual phase correction using FRING
  CHINC......< 0 -> set CHINC in FRING to 0.5E6 / (FREQ increment).
                    One is used for all but narrow-band spectroscopy
             Channel increment in fitting - note channels are averaged
             etc.  This reduces the memory requirements and is
             suitable for delay errors that are not too large to cause
             channel-to-channel loss of coherence.


VLBAPCOR:           Procedure to correct the instrumental phases
                    using the pulse cals in the PC table.  It can
                    also finds the instrumental phases for antennas
                    not in PC table using FRING.
Documenter:         Amy Mioduszewski

This should be done after sampler corrections (VLBACCOR) and
before the bandpass (VLBABPSS).  After VLBAMPCL is run it is
ESSENTIAL to check the solutions in POSSM setting GAINUSE to
the CL table output by VLBAPCOR.

VLBAPCOR assumes:

1. there is only one FREQID

2. that all IFs should be calibrated

3. that the highest PC table is the one to apply

4. MBDELY is not zero (see EXPLAIN PCCOR).

If you want a manual instrumental phase correction on
antennas that are not in the PC table (OPCODE='CALP'
and ANTENNAS <> 0) then there are these additional

5. that ANTENNAS have strong fringes on the input TIMERANGE

6. that the highest FG table is the one that should be applied

Steps in VLBAPCOR:

 1. Runs PCCOR, which takes the PC table with the highest #  and
    calculates the instrumental phases and delays from the pulse-
    calibration tones.  The TIMERANGE is needed to solve 2pi*N
    ambiguities but the solutions are calculated using the
    pulse-cal tones over all times.  PCCOR produces a SN table.
    Output should be highest SN table.

*2. Runs SNCOR twice, to zero the phases and delays (OPCODE=
    ZPHS, ZDEL' of the SN table created by PCCOR for the
    antennas in ANTENNAS if OPCODE='CALP'.

 3. Runs CLCAL, with input OPCODE; ANTENNAS=0; INTERPOL='';
    SNVER= SN table out of PCCOR; GAINVER = input GAINUSE;
    and GAINUSE= highest CL table +1.  Output should be highest
    CL table.

*4. Runs FRING, using the GAINUSE used in CLCAL in step 2.
    DPARM(8)=1 to zero rates.  If FRING reports any "failed
    solutions" you MUST find another scan and run again, after
    you have deleted the SN and CL tables that VLBAPCOR has
    created.  Unless there is a good reason for failed solutions,
    such as an entire IF has been flagged for a certain antenna.

*5. Runs CLCAL with ANTENNAS equal to the input ANTENNAS
    GAINVER equal to input GAINUSE; SNVER equal to output
    SN table from FRING; GAINUSE equal to the CL table
    which is output in step 2; TIMERANGE =0; and
    CALSOUR = ''.

*NOTE: Steps 2, 4 and 5 only take place if OPCODE='CALP' and

If you want to do manual phase instrumental corrections for
antennas missing from PC table after VLBAPCOR (there are many
good reason to want to do this, such as wanting to use a
different time range or KRING):

1. Make sure that OPCODE='CALP' when you run VLBAPCOR.

2. When you run FRING or KRING be sure:
       - to pick a TIMERANGE that has strong fringes on the
         antennas you wish to correct
       - the REFANT is the same as in VLBAPCOR
       - GAINUSE is equal to the CL table that is produced
          by VLBAPCOR, and DOCAL=2
       - in FRING: DPARM(8)=1
         in KRING: OPCODE='ZRAT'
       - ANTENNAS can be either the antennas you want to
         fit + REFANT or all the antennas
       - when you run FRING/KRING there are no failed solutions
         on the antennas you want to correct.

3. When you run CLCAL be sure:
       - ANTENNAS are ONLY the antennas you want to correct,
         do NOT put the REFANT in this list
       - REFANT is the same as in VLBAPCOR
       - SNVER is SN table out of FRING/KRING
       - GAINVER is the GAINUSE you used in VLBAPCOR,
         i.e. the CL table with all the calibration EXCEPT
         the instrumental phase corrections.
       - GAINUSE is the CL table output from VLBAPCOR (and
         that you used are GAINUSE in FRING/KRING).
       - TIMERANGE = 0
       - CALSOUR = ''
       - OPCODE = 'CALI'

For antennas that are present in the PC table but the pulse cals
do not correct things satisfactorily:

1. Delete the CL table created by VLBAPCOR using EXTD and
   then do one of 2 things:


   Run SNCOR twice:
       - set SNVER to the SN table created by VLBAPCOR
       - set ANTENNAS to the antennas that were not satisfactory
       - set OPCODE = 'ZPHS'
       - all other adverbs should be defaults
       - run SNCOR
       - set OPCODE = 'ZDEL'
       - run SNCOR
   Run CLCAL:
       - SNVER is SN table out of VLBAPCOR
       - GAINVER is the GAINUSE you used in VLBAPCOR,
         i.e. the CL table with all the calibration EXCEPT
         the instrumental phase corrections.
       - GAINUSE = highest CL table +1
       - TIMERANGE = 0
       - CALSOUR = ''
       - OPCODE = 'CALP'
   Then do steps 2 & 3 from the case where there are antennas
   missing from the PC table.


   Delete the SN table created by VLBAPCOR using EXTD and rerun
   VLBAPCOR with the 'bad' antennas in the ANTENNAS list.  Then
   you are done.