AIPS HELP file for VLBAKRNG in 31DEC21
As of Tue Jan 26 12:00:56 2021
VLBAKRNG: Procedure to fringe fit and calibrate data
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
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 Subarray 0=>all
SEARCH 0.0 1000.0 Prioritized reference antenna
list - supplements REFANT
SOLINT Solution interval (min)
0 => 10 min
OPCODE 'ZDEL' => zero delays
for more, See HELP KRING
FOR SPEC. LINE EXP. ONLY
CPARM for strong sources, it is
only necessary to set
CPARM(1) and CPARM(8).
1 min. int. time (sec) 0 => 2
8 <=0 rereference solutions
this should be 1 for
for rest see HELP VLBAKRNG
SOURCES Source list to calibrate: If
sources are listed they are
each calibrated with separate
runs of CLCAL
INTERPOL Interpolation function:
BADDISK 0.0 15.0 Disk no. not to use for
Use: This procedure does antenna based fringe fitting using KRING
and then applies those corrections using CLCAL. For more
information on KRING and CLCAL see their respective HELP/EXPLAIN
files. If you are doing a phase reference experiment use
Type RUN VLBAUTIL to make the VLBAKRNG 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.
CALSOUR....List of sources for which calibration constants are to be
determined, i.e. the calibrator sources All ' ' = all
sources; a "-" before a source name. means all except ANY
source named. Note: solutions for multiple sources can
only be made if the sources are point sources at their
assumed phase center and with the flux densities given in
the source (SU) table.
TIMERANG...Time range of the data to be used. In order: Start day,
hour, min. sec, end day, hour, min. sec. Days relative to
BCHAN......First channel to use. 0=>all.
ECHAN......Highest channel to use. 0=>all higher than BCHAN
GAINUSE....(multisource) version number of the CL table to apply to
the data. 0 => highest.
REFANT.....The desired reference antenna for phases. Note that
the desired refant is not required to be the primary search
antenna. You should choose the REFANT to be an antenna
that is present during most of the observation.
SUBARRAY...Subarray number to use. 0=>all.
SEARCH.....List of prioritized reference antennas to be used for
fringe searching during the FFT stage. KRING constructs
an internal search list to determine the order in which to
perform the FFTs. This search list is constructed by first
copying the elements of SEARCH. Finally, all remaining
antennas antennas are appended to the search list in
numerical order. You can limit the search to only the
specified elements of the SEARCH list by setting CPARM(6).
Only baselines where at least one antenna appears in the
search list will be searched for fringes.
You should explicitly order the antennas in terms of decreasing
sensitivity if at all possible.
SOLINT.....The solution interval. Note that this is only a
recommended solution interval. The actual solution interval
used by KRING will be changed in order to divide each scan
evenly into an integral number of data chunks.
SOLINT is in minutes; the default value (SOLINT=0) is 10
minutes. SOLINT values larger than 10 are reset to 10 minutes
unless CPARM(9)>0. NB: If SOLINT > 0.75*Scan, SOLINT = Scan.
OPCODE.....Solution masking to be performed _after_ fringe-fitting
' ' no masking
'ZPHS' zero phases in output SN table
'ZRAT' zero rates in output SN table
'ZDEL' zero delays in output SN table
If CPARM(8)>0, OPCODE is forced = ' '.
If this is not a spectral line experiment leave this
as the default.
CPARM......CPARM(1) and CPARM(8) are the only CPARMs that it is essential
to set, for strong sources the rest can be left as default.
CPARM(1)...The minimum integration time of the data (sec);
0 => 2 'VLBA' seconds
It is important to get this number right to within 20 percent.
E.g., if you've averaged up 1 second data to 10 seconds,
setting this to 10 is okay so long as there are only a
very few points with shorter than 10 second integration
times. If you set this to 1 second, you will regret it.
CPARM(2)...The delay window FW to search (nsec) centered on 0 delay.
<= 0 => full Nyquist range.
[Use SOLMOD to turn off the delay search.]
CPARM(3)...The rate window FW to search (mHz) centered on 0 rate.
<= 0 => full Nyquist range.
[Use SOLMOD to turn off the rate search.]
CPARM(4)...The minimum allowed signal-to-noise ratio. <0 => 3
The SNR calculation is described in AIPS Memo 101.
[You might consider setting this to 5.]
CPARM(5)...Number of baseline combinations to use in the initial,
FFT 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.
[Solutions formed using combinations of baselines are
marked with a plus for singly indirect combinations and
with two pluses for doubly indirect combinations.]
CPARM(6)...If CPARM(6)=1, only baselines to those antennas on the
SEARCH list are searched during the FFT stage. Otherwise,
other baselines are eventually searched until either fringes
have been found to each antenna, or no baselines remain to
CPARM(7)...If >0, RR and LL data are averaged together and only a
single solution is determined for both polarizations. This
is useful when reducing polarization data.
CPARM(8)...If <= 0 then the phase, rate and delays will be
re-referenced to a common antenna. CPARM(8)=1 is only
desirable for VLBI polarization data. Using this option also
forces OPCODE = ' '.
CPARM(9)...If SOLINT>10 is desired, you must set CPARM(9)>0 . This
is necessary to prevent accidentally requesting more memory
than your computer can deliver and locking up computer.
CPARM(10)..Try Hard Option. If CPARM(10)>=0, When KRING is ready to
do the initial FFT-based fringe search, it will first try
to initialize residual fringe-fit delay and rate solns for
each antenna using an average of all good solutions found
in the SN table. Only those antennas for which acceptable
solutions are not found will then be FFTd to find fringes.
This does not preclude the final Least Squares refinement.
[20 Oct 1999, it has been reported that CPARM(10) is broken -
it may trash the solutions - dont try it unless you have
the time to re-run KRING if need-be.]
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). If sources are listed
then CLCAL is run once for each source using the
interpolation method stated in INTERPOL. This
second option is recommended, see EXPLAIN file.
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.
'SELF' = Use only SN solution from same source which
is closest in time.
'SIMP' = Simple linear phase connection between SN phase
entries, assumes phase difference less than 180
'AMBG' = Linear phase connection using rates to resolve
'CUBE' = As AMBG but fit third order polynomial to phases
BADDISK....A list of disk numbers to be avoided when creating scratch
VLBAKRNG: Procedure to perform antenna based fringe fitting
using KRING and then apply these corrections using
CLCAL. If you are doing phase referencing use
Documenter: Amy Mioduszewski
Related Programs: VLBAUTIL, KRING, CLCAL, VLBAFRNG, VLBAKRGP
This should be done after solving for the instrumental phase
corrections (VLBAPCOR) and before applying all the calibration
and averaging (SPLIT/SPLAT). After VLBAKRNG is run it is ESSENTIAL
to check the solutions in POSSM setting GAINUSE to the CL table
output by VLBAKRNG. VLBAKRNG will produce the highest SN and
CL table. For details on KRING and CLCAL see their HELP/EXPLAIN
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 VLBAKRNG:
1. Runs KRING, 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
KRING; 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. If SOURCES is not blank then CLCAL
will be run for each SOURCE individually setting both CALSOUR
and SOURCES to the same single source in the SOURCES list.
This is recommended because of CLCAL is run for all the sources
at once with any INTERPOL except 'SELF' then incorrect
solutions may be applied for a few minutes before and after a
source change. CLCAL will output the highest CL table.
After VLBAKRNG is run and the solutions are checked in POSSM SPLIT
or SPLAT should be run with GAINUSE set to the CL output from VLBAKRNG