AIPS HELP file for VHCALIB in 31DEC24
As of Mon May 6 6:52:03 2024
VHCALIB: CALIB with I, Q, U, models for linear polarization
INPUTS
INNAME Input UV data name (name)
INCLASS Input UV data name (class)
INSEQ 0.0 9999.0 Input UV data name (seq. #)
INDISK 0.0 9.0 Input UV data disk unit #
IN2NAME Input I model name (name)
IN2CLASS Input I model name (class)
IN2SEQ 0.0 9999.0 Input I model name (seq. #)
IN2DISK 0.0 9.0 Input I model disk unit #
IN3NAME Input Q model name (name)
IN3CLASS Input Q model name (class)
IN3SEQ 0.0 9999.0 Input Q model name (seq. #)
IN3DISK 0.0 9.0 Input Q model disk unit #
IN4NAME Input U model name (name)
IN4CLASS Input U model name (class)
IN4SEQ 0.0 9999.0 Input U model name (seq. #)
IN4DISK 0.0 9.0 Input U model disk unit #
CALSOUR (1) Calibration source name
DOCALIB -1.0 101.0 > 0 calibrate data & weights
> 99 do NOT calibrate weights
GAINUSE CL (or SN) table to apply
FLAGVER Flag table version
DOBAND -1.0 10.0 If >0 apply bandpass cal.
Method used depends on value
of DOBAND (see HELP file).
BPVER Bandpass table version
SOLINT Averaging interval
SOLTYPE Soln type,' ','L1','GCON',
'R', 'L1R', 'GCOR'
BADDISK Disk to avoid for scratch
V_DEBUG > 0 -> inquire at each task
< 0 -> delete temp files
HELP SECTION
VHCALIB
Procedure: It makes matching model data sets in I, Q, and U
polarization with SPLIT and UVSUB. Then it divides a linear
polarization model into the V and H input data. Finally it
runs CALIB on the divided data set and copies the resulting
SN table back to the input UV data set.
The model is
VV = I + Q cos(p1+p2) + U sin (p1+p2)
HH = I - Q cos(p1+p2) - U sin (p1+p2)
where p1 and p2 are the two antennas' parallactic angles
(functions of time) and I, Q, U are the Stokes visibility
functions of location in the u,v plane.
The input images should contain Clean Component files for
computing the Stokes model visibilities.
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.
IN2NAME....Input I image name (name). Standard defaults.
IN2CLASS...Input I image name (class). Standard defaults.
IN2SEQ.....Input I image name (seq. #). 0 => highest.
IN2DISK....Disk drive # of input I image. 0 => any.
IN3NAME....Input Q image name (name). Standard defaults.
IN3CLASS...Input Q image name (class). Standard defaults.
IN3SEQ.....Input Q image name (seq. #). 0 => highest.
IN3DISK....Disk drive # of input Q image. 0 => any.
IN4NAME....Input U image name (name). Standard defaults.
IN4CLASS...Input U image name (class). Standard defaults.
IN4SEQ.....Input U image name (seq. #). 0 => highest.
IN4DISK....Disk drive # of input U image. 0 => any.
CALSOUR....(1) Calibration source name. (2)-(30) ignored.
DOCALIB....If true (>0), calibrate the data using information in the
specified Cal (CL) table for multi-source or SN table for
single-source data. Also calibrate the weights unless
DOCALIB > 99 (use this for old non-physical weights).
GAINUSE....version number of the CL table to apply to
multi source files or the SN table for single
source files. 0 => highest.
FLAGVER....Specifies the version of the flagging table to be
applied. 0 => highest numbered table. <0 => no flagging
to be applied.
DOBAND.....If true (>0) then correct the data for the shape of the
antenna bandpasses using the BP table specified by BPVER.
The correction has five modes:
(a) if DOBAND=1 all entries for an antenna in the table
are averaged together before correcting the data.
(b) if DOBAND=2 the entry nearest in time (including
solution weights) is used to correct the data.
(c) if DOBAND=3 the table entries are interpolated in
time (using solution weights) and the data are then
corrected.
(d) if DOBAND=4 the entry nearest in time (ignoring
solution weights) is used to correct the data.
(e) if DOBAND=5 the table entries are interpolated in
time (ignoring solution weights) and the data are then
corrected.
BPVER......Specifies the version of the BP table to be applied if
DOBAND > 0. 0 => highest numbered table.
<0 => no bandpass correction to be applied.
SOLINT.....The solution interval (min.)
0 => scan average for multi-source,
0 => 10 s for single source amp-phase solns. (VLA)
0 => 10 min for delay-rate solutions (VLBA).
CALIB tries hard to make equal integrations within each
scan but that is a problem that lacks a general solution.
You can help by careful choice of SOLINT: assume you have
data every 10 seconds. Then, to get 1 sample per
solution, set SOLINT=9/60. To get 2 per solution, set
SOLINT=19/60, 3 per solution SOLINT=29/60. Each averaged
interval will start with an actual data sample and will
end just before the first sample at a time greater than
the start + SOLINT + 0.1s. At the end of the scan, the
end time can be increased by up to 0.6 * SOLINT to
prevent short final integrations. For calibration that
is not self-calibration, note that the 2-point
interpolation will use ONLY the last integration of a
calibrator scan with the first integration of the next
calibrator sacn. That is why the initial calibration
normally uses scan averages for the calibrator sources.
-------------------------
If the times in your data set are not at regular
intervals due to flagging and averaging, you must be
careful with SOLINT. To get all data in 10 seconds (from
0 through 9.999) set SOLINT to 9.999/60. Use of 1 sec
will do odd things with the records at odd times.
-------------------------
SOLTYPE....Solution type:
' ' => normal least squares,
'R ' => as ' ' with robust iteration
'L1 ' => L1 solution; a weighted sum of the moduli
of the residuals is minimized.
The computed gain solutions are less
influenced by wild data points, but there
is some loss of statistical efficiency.
See [F.R. Schwab, VLA scientific Memo #136]
for further details.
'L1R ' => as 'L1' with robust iteration
BADDISK....Disk drives to avoid for scratch files.
V_DEBUG....> 0 => show the inputs for each task before running the
task and ask if you want to stop (answer 0) or
simply go on (anything else)
< 0 => Clean out all data sets made during the procedure.
EXPLAIN SECTION