; XYMOD ;--------------------------------------------------------------- ;! Compute linear polarization point source model, applies to data ;# Task UV Calibration ;----------------------------------------------------------------------- ;; Copyright (C) 2019 ;; Associated Universities, Inc. Washington DC, USA. ;; ;; This program is free software; you can redistribute it and/or ;; modify it under the terms of the GNU General Public License as ;; published by the Free Software Foundation; either version 2 of ;; the License, or (at your option) any later version. ;; ;; This program is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;; GNU General Public License for more details. ;; ;; You should have received a copy of the GNU General Public ;; License along with this program; if not, write to the Free ;; Software Foundation, Inc., 675 Massachusetts Ave, Cambridge, ;; MA 02139, USA. ;; ;; Correspondence concerning AIPS should be addressed as follows: ;; Internet email: aipsmail@nrao.edu. ;; Postal address: AIPS Project Office ;; National Radio Astronomy Observatory ;; 520 Edgemont Road ;; Charlottesville, VA 22903-2475 USA ;----------------------------------------------------------------------- XYMOD LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC XYMOD Computes linear polarization point source model 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 # SOURCES Source name QUAL -10.0 Calibrator qualifier -1=>all CALCODE Calibrator code ' '=>all TIMERANG Time range to use SELBAND Bandwidth to select (kHz) SELFREQ Frequency to select (MHz) FREQID Freq. ID to select. ANTENNAS Antennas to copy 0=>all BASELINE Baselines with ANTENNAS SUBARRAY 0.0 1000.0 Sub-array, 0=>all BIF Low IF number to do EIF Highest IF number to do BCHAN 0.0 First channel included ECHAN 0.0 last channel included DOCALIB -1.0 101.0 > 0 calibrate data & weights > 99 do NOT calibrate weights GAINUSE CL (or SN) table to apply DOPOL -1.0 10.0 If >0.5 correct polarization. PDVER PD table to apply (DOPOL>0) BLVER BL table to apply. FLAGVER Flag table version DOBAND -1.0 10.0 If >0.5 apply bandpass cal. Method used depends on value of DOBAND (see HELP file). BPVER Bandpass table version SMOOTH Smoothing function. See HELP SMOOTH for details. DOACOR Include autocorrelations? OUTNAME Output UV file name (name) OUTCLASS Output UV file name (class) OUTSEQ -1.0 9999.0 Output UV file name (seq. #) OUTDISK 0.0 9.0 Output UV file disk unit #. FQCENTER >= 0 -> center frequency axis BADDISK Disks to avoid for scratch OPCODE 'MODL', 'SUBT', else division ROTATE Rotation measure in rad/m^2 ---------------------------------------------------------------- XYMOD Task: This task computes a linear polarization model and then applies it to the input data, either dividing the input by the model, subtracting the model, or replacing the data with the model. The model is computed as follows: Q(i) = Qt cos (2 d) - Ut sin (2 d) U(i) = Qt sin (2 d) + Ut cos (2 d) where Qt is the true Q, Ut the true U, and d = RM lambda(i)^2 and Qt and Ut are taken from the source table. Then Vxx = I + Q(i) cos (2 P) + U(i) sin (2 P) Vyy = I - Q(i) cos (2 P) - U(I) sin (2 P) where Vxx and Vyy are the model fluxes in the parallel hands and P is the parallactic angle. Note: we assume the same parallactic angle for both antennas which is good enough for the VLA. 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. SOURCES....Source to be copied. ' '=> all; if any starts with a '-' then all except ANY source named. QUAL.......Qualifier of source to be copied. -1 => all. CALCODE....Calibrator code of sources to copy. ' '=> all. TIMERANG...Time range of the data to be copied. In order: Start day, hour, min. sec, end day, hour, min. sec. Days relative to ref. date. SELBAND....Bandwidth of data to be selected. If more than one IF is present SELBAND is the width of the first IF required. Units = kHz. For data which contain multiple bandwidths/frequencies the task will insist that some form of selection be made by frequency or bandwidth. SELFREQ....Frequency of data to be selected. If more than one IF is present SELFREQ is the frequency of the first IF required. Units = MHz. FREQID.....Frequency identifier to select (you may determine which is applicable from the OPTYPE='SCAN' listing produced by LISTR). If either SELBAND or SELFREQ are set, their values override that of FREQID. However, setting SELBAND and SELFREQ may result in an ambiguity. In that case, the task will request that you use FREQID. ANTENNAS...A list of the antennas to be copied. All 0 => all. If any number is negative then all antennas listed are NOT to be copied and all others are. BASELINE...Baselines between antennas named in ANTENNAS and those named in BASELINE are selected.. There are four possible combinations of ANTENNAS and BASELINE: 1. ANTENNAS = 0; BASELINE = 0. All possible baselines are selected. 2. ANTENNAS <>0; BASELINE = 0. a)All ANTENNAS > 0 Baselines including an antenna in the ANTENNAS list are selected; b)Some ANTENNAS < 0 All baselines NOT including an antenna in the ANTENNAS list are selected; 3. ANTENNAS = 0; BASELINE <> 0. a)All BASELINE > 0 Baselines including an antenna in the BASELINE list are selected; b)Some BASELINE < 0 All baselines NOT including an antenna in the BASELINE list are selected; 4. ANTENNAS <> 0; BASELINE <> 0. a)All ANTENNAS>0 and all BASELINE>0 Baselines between antennas named in ANTENNAS and those named in BASELINE are selected. b)Some ANTENNAS<0 .OR. some BASELINE<0 Baselines between antennas named in ANTENNAS and those named in BASELINE are DE-selected, all others are selected. SUBARRAY...Sub-array number to copy. 0=>all. BIF........First IF to include. 0 -> 1. EIF........Last IF to include. 0 -> max. BCHAN......First channel to copy. 0=>all. ECHAN......Highest channel to copy. 0=>all higher than BCHAN 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. DOPOL......If > 0 then correct data for instrumental polarization as represented in the AN or PD table. This correction is only useful if PCAL has been run or feed polarization parameters have been otherwise obtained. See HELP DOPOL for available correction modes: 1 is normal, 2 and 3 are for VLBI. 1-3 use a PD table if available; 6, 7, 8 are the same but use the AN (continuum solution) even if a PD table is present. PDVER......PD table to apply if PCAL was run with SPECTRAL true and 0 < DOPOL < 6. <= 0 => highest. BLVER......Version number of the baseline based calibration (BL) table to apply. <0 => apply no BL table, 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. IMAGR uses DOBAND as the nearest integer; 0.1 is therefore "false". BPVER......Specifies the version of the BP table to be applied 0 => highest numbered table. <0 => no bandpass correction to be applied. SMOOTH.....Specifies the type of spectral smoothing to be applied to a uv database . The default is not to apply any smoothing. The elements of SMOOTH are as follows: SMOOTH(1) = type of smoothing to apply: 0 => no smoothing To smooth before applying bandpass calibration 1 => Hanning, 2 => Gaussian, 3 => Boxcar, 4 => Sinc To smooth after applying bandpass calibration 5 => Hanning, 6 => Gaussian, 7 => Boxcar, 8 => Sinc SMOOTH(2) = the "diameter" of the function, i.e. width between first nulls of Hanning triangle and sinc function, FWHM of Gaussian, width of Boxcar. Defaults (if < 0.1) are 4, 2, 2 and 3 channels for SMOOTH(1) = 1 - 4 and 5 - 8, resp. SMOOTH(3) = the diameter over which the convolving function has value - in channels. Defaults: 1,3,1,4 times SMOOTH(2) used when input SMOOTH(3) < net SMOOTH(2). DOACOR.....> 0 => include autocorrelations as well as cross correlation data. OUTNAME....Output UV file name (name). Standard defaults. OUTCLASS...Output UV file name (class). Standard defaults. OUTSEQ.....Output UV file name (seq. #). 0 => highest unique OUTDISK....Disk drive # of output UV file. 0 => highest with space for the file. FQCENTER,..> 0 => Change frequency axis reference pixel to Nchan / 2 + 1 else => do not change reference pixel BADDISK....The disk numbers to avoid for scratch files (sorting tables mostly). OPCODE.....'MODL' writes out the model values ignoring the input visibilities. 'SUBT' subtracts the model values from the input visibilities. else divides the model values into the input visibilities. ROTATE.....Rotation measure (RM above) in radians per meter squared. ----------------------------------------------------------------