AIPS HELP file for VLBAFRGP in 31DEC24
As of Fri Apr 26 8:32:04 2024
VLBAFRGP: Procedure to fringe fit and calibrate phase ref. data
INPUTS
Input uv data.
INNAME UV file name (name)
INCLASS UV file name (class)
INSEQ 0.0 9999.0 UV file name (seq. #)
INDISK 0.0 9.0 UV file disk drive #
CALSOUR Source list to fringe fit
NO DEFAULT
TIMERANG Time range to use.
BCHAN 0.0 2048.0 Lowest channel number 0=>all
FOR SPEC. LINE EXP. ONLY
ECHAN 0.0 2048.0 Highest channel number
FOR SPEC. LINE EXP. ONLY
GAINUSE CL table to apply.
REFANT Reference antenna
SUBARRAY 0.0 1000.0 Subarray, 0=>all
SEARCH 0.0 1000.0 Prioritized reference antenna
list - supplements REFANT
SOLINT Solution interval (min)
0 => 10 min
DPARM for strong sources, it is
only necessary to set
DPARM(4), DPARM(7) and for
spec line exp DPARM(8).
4=int. time (sec)
0 => min. found in data
7 >0 => don't rereference
phase; this should be 1
for polarization exp
8 > 0 => activate zero'ing
options
for rest see HELP VLBAFRGP
SOURCES Source list to calibrate: Any
sources in the SOURCE list
that are not in the CALSOUR
list will be phase referenced
to the FIRST source in the
CALSOUR list.
CHINC 1.0 Channel increment in FRING
< 0 -> find from data
INTERPOL Interpolation function:
'2PT','SIMP','AMBG','CUBE',
BADDISK 0.0 15.0 Disk no. not to use for
scratch files.
HELP SECTION
VLBAFRGP
Type: Procedure
Use: This procedure does antenna based fringe fitting for phase
referencing experiments using FRING and then applies those
corrections using CLCAL. For more information on KRING and
CLCAL see their respective HELP/EXPLAIN files.
Type RUN VLBAUTIL to make the VLBAFRGP 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.
CALSOUR....List of sources for which calibration constants are to be
determined. The default is not permitted nor are '-'
sources, as you must select a phase reference source. The
FIRST source in the list is the phase reference source and
will be used to phase reference any sources in the SOURCES
list that are NOT in the CALSOUR list.
TIMERANG...Time range of the data to be used. In order: Start day,
hour, min. sec, end day, hour, min. sec. Days relative to
reference date.
BCHAN......First channel to use. 0=>all. If this is not a spectral
line experiment, leave as default.
ECHAN......Highest channel to use. 0=>all higher than BCHAN. If this
is not a spectral line experiment, leave as default.
GAINUSE....(multisource) version number of the CL table to apply to
the data. 0 => highest.
REFANT.....The desired reference antenna for phases.
SUBARRAY...Subarray number to use. 0=>all.
SEARCH.....List of Prioritized antennas to be used when APARM(9)>0.
This adverb supplements REFANT. It is recommended that
SEARCH be filled with a list of antennas whose order
reflects the user's notion of which baselines will be
easiest to find fringes on. All baselines to each antenna
in SEARCH will be searched in order looking for fringes.
All remaining baselines will then be searched. Choosing
SEARCH wisely will speed the FFT portion of FRING. The
antenna chosen in REFANT is treated as SEARCH(0), ie all
baselines to it are searched first.
SOLINT.....The solution interval (min.) You really should set this;
longer values are allowed beginning with 15OCT96.
0 => 10 minutes for all inputs
If SOLINT > Scan/2 (in Multisource) SOLINT = Scan.
DPARM......Delay rate parameters. For strong sources the only
essential DPARMS are 4, 7 and 8. 8 is only important
for spectral line experiments.
DPARM(1)...Number of baseline combinations to use in the initial,
coarse fringe search (1-3). Larger values increase the
point source sensitivity but reduce the sensitivity to
extended sources when an accurate model is not available.
0=>3.
DPARM(2)...The delay window to search (nsec) centered on 0 delay.
0 => full Nyquist range defined by the frequency spacing.
If DPARM(2) < 0.0 no delay search will be performed.
DPARM(3)...The rate window to search (mHz) centered on 0 rate.
0 => full Nyquist range defined by the integration time.
DPARM(4)...The minimum integration time of the data (sec);
0 => search the data to find the minimum integration
time.
The correct minimum of all baselines should be supplied.
DPARM(5)...If > 0 then don't do the least squares solution. If the
least squares solution is not done then only the coarse
search is done and much less accurate solutions are
obtained.
DPARM(6)...If > 0 then the output data will not be averaged in
frequency else, all frequencies in each IF will be
averaged. Affects single source files only.
DPARM(7)...If > 0 then the phase, rate and delays will not be
re-referenced to a common antenna. This option is only
desirable for VLBI polarization data.
DPARM(8)...DPARM(8)>0 allows zero'ing of RATE, DELAY, and/or PHASE
solutions. ** Note that the ZEROing is done _AFTER_ the
FRING solution is found, this is not the mechanism for
turning off the DELAY, RATE, or PHASE search, see
DPARM(2-3) for that capability. **
DPARM(8) value zero RATES? zero DELAYs? zero PHASEs?
0 No No No
1 Yes No No
2 No Yes No
3 Yes Yes No
4 No No Yes
5 Yes No Yes
6 No Yes Yes
7 Yes Yes Yes
SOURCES....Sources to calibrate. If this is left blank then all
the sources are calibrated at once using the INTERPOL
(i.e. CLCAL is only run once) and phase referenced to the
FIRST source in the CALSOUR list. If sources are listed
then CLCAL is run once for each source using the
interpolation method stated in INTERPOL. Any sources
that are in the SOURCE list but not in the CALSOUR list
will be phase referenced to the FIRST source in the
CALSOUR list.
CHINC......< 0 -> set CHINC 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.
INTERPOL...The type of interpolation to be applied to the SN table:
' ' = linear vector interpolation with no SN smoothing.
'2PT ' = linear vector interpolation with no SN smoothing.
'SIMP' = Simple linear phase connection between SN phase
entries, assumes phase difference less than 180
degrees.
'AMBG' = Linear phase connection using rates to resolve
phase ambiguities.
'CUBE' = As AMBG but fit third order polynomial to phases
and rates.
BADDISK....A list of disk numbers to be avoided when creating scratch
files.
EXPLAIN SECTION
VLBAFRGP: Procedure to perform antenna based fringe fitting
for phase referenced data using FRING and then apply
these corrections using CLCAL.
Documenter: Amy Mioduszewski
Related Programs: VLBAUTIL, FRING, CLCAL, VLBAKRGP, VLBAFRNG
This should be done after solving for the instrumental phase
corrections (VLBAPCOR) and before applying all the calibration
and averaging (SPLIT/SPLAT). After VLBAFRGP is run it is ESSENTIAL
to check the solutions in POSSM setting GAINUSE to the CL table
output by VLBAFRGP. VLBAFRGP will produce the highest SN and
CL table. For details on FRING and CLCAL see their HELP/EXPLAIN
files.
It should be noted that this procedure will do the same thing as
VLBAFRNG if all SOURCES are in the CALSOUR list. In order to have
the target source phase referenced it must be missing from the CALSOUR
list and in the SOURCES list or, alternatively, the SOURCES list must be
left blank. The first option caused the sources listed in SOURCES but
missing from CALSOUR to be phase referenced to CALSOUR(1), while the
second caused ALL the sources to be phase referenced to CALSOUR(1).
VLBAFRGP assumes:
1. there is only one FREQID
2. that all IFs should be calibrated
3. that all antennas should be calibrated
4. that the entire uv range should be calibrated
5. that the highest FG table is the one that should be applied
6. that this is a multisource file
Steps in VLBAFRGP:
1. Runs FRING, which will do antenna based fringe fits. This
will produce the highest SN table.
2. Runs CLCAL, with OPCODE 'CALI', SNVER output SN table from
FRING; GAINVER input GAINUSE and GAINUSE = highest CL table +1.
Output should be highest CL table. If SOURCES is blank then
CLCAL is run only once and phase referenced to CALSOUR(1). If
SOURCES is not blank then CLCAL is run for each source in
SOURCES. If the source in SOURCES is in the CALSOUR list then
it is referenced to itself, if not it is phase referenced to
CALSOUR(1).
After VLBAFRGP is run and the solutions are checked in POSSM SPLIT
or SPLAT should be run with GAINUSE set to the CL output from VLBAFRGP
and DOCAL=2.