AIPS HELP file for VLBAPCOR in 31DEC24
As of Tue Apr 23 22:40:50 2024
VLBAPCOR: Procedure to correct instrumental phases
INPUTS
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
incorrect).
CHINC 1.0 Channel increment in FRING
< 0 -> find from data
HELP SECTION
VLBAPCOR
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
available.
Adverbs:
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
experiment
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
data.
Channel increment in fitting - note channels are averaged
BCHAN to BCHAN+CHINC-1, BCHAN+CHINC to BCHAN+2*CHINC-1,
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.
EXPLAIN SECTION
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
Related Programs: VLBAUTIL, PCCOR, CLCAL, PCLOD, FRING, SNCOR
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
assumptions:
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
ANTENNAS <> 0.
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:
2. *EITHER*
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.
*OR*
Delete the SN table created by VLBAPCOR using EXTD and rerun
VLBAPCOR with the 'bad' antennas in the ANTENNAS list. Then
you are done.