; XYDIF ;--------------------------------------------------------------- ;! find/apply X minus Y linear polarization phase difference ;# Task UV Calibration polarization ;----------------------------------------------------------------------- ;; Copyright (C) 2018 ;; 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 ;----------------------------------------------------------------------- XYDIF LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC XYDIF: Task to return/apply X - Y linear pol. phase difference INNAME UV data (name). INCLASS UV data (class). INSEQ 0.0 9999.0 UV data (seq. #). 0 => high INDISK Disk unit #. 0 => any CALSOUR Calibration source list CALCODE Calibrator code ' '=>all TIMERANG Time range to list SELBAND Bandwidth to select (kHz) SELFREQ Frequency to select (MHz) FREQID Freq. ID to select. None selected => 1. BIF 0.0 100.0 Lowest IF number 0=1 EIF 0.0 100.0 Highest IF number BCHAN 0.0 2048.0 Low channel number 0=>1 ECHAN 0.0 2048.0 High channel number ANTENNAS Antennas to list UVRANGE 0.0 UV range in kilolambda SUBARRAY 0.0 1000.0 Subarray, 0=>1 Cal. info for input: DOCALIB -1.0 101.0 > 0 calibrate data & weights > 99 do NOT calibrate weights GAINUSE CAL (CL or SN) table to apply DOPOL -1.0 10.0 If >0 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 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. DOINVERS -1.0 1.0 > 0 -> add 180 to solutions DOAPPLY -1.0 1.0 > 0 => apply to CL or BP table now SPECTRAL -1.0 1.0 > 0 do spectral solution using PD table INTPARM Smoothing parameters for spectral mode DOPRINT -3.0 132.0 > 0 -> use the terminal, else use the line printer > 72 => terminal width = 0 -> no printing OUTPRINT Printer disk file to save BADDISK Disk to avoid for scratch. CLCORPRM @ X-Y phase difference returned if SPECTRAL <= 0 ---------------------------------------------------------------- XYDIF Type: Task Use: Determines the X minus Y linear polarization phase difference by comparing the phases of the U and V Stokes visibilities in the frame of the antenna rather than the source. The phase difference is ATAN2 (V,U), as a function of IF and/or spectral channel. Note that this phase difference arises because the X and Y phases are separately referenced with nothing in CALIB and BPASS to force the two to a common reference. Note that this function requires a linearly polarized source with no circular polarization. The phase difference causes U to rotate into V. XYDIF can be run in an IF-dependent fashion (SPECTRAL <= 0). In this mode, it can print matrix listings of U and V which can be examined for bad data and/or other issues. XYDIF returns the mean phases in the CLCORPRM adverb. Unlike RLDIF, these values need no correction before they are used in CLCOR. The printing in XYDIF may be suppressed. Set DOAPPLY=1 for this. A new CL table is created. XYDIF may also be used in a fully channel-dependent mode (SPECTRAL > 0). In this mode, the matrix printing is suppressed, but the answers and rmses may be (should be) printed. If DOAPPLY > 0, the BP table is corrected, with a new version being written. The RMSes printed are meant to be the uncertainties in the mean values. Adverbs: INNAME.....UV file name (name). Standard defaults. INCLASS....UV file name (class). Standard defaults. INSEQ......UV file name (seq. #). 0 => highest. INDISK.....Disk unit #. 0 => any. CALSOUR....List of calibration sources to be used. ' '=> all; if any starts with a '-' then all except ANY source named. CALCODE....Calibrators may be selected on the basis of the calibrator code given in the SU table. ' ' => any calibrator code selected '* ' => any non blank code (cal. only) '-CAL' => blank codes only (no calibrators) anything else = calibrator code to select. NB: The CALCODE test is applied in addition to the other selection tests TIMERANG...Time range of the data to be used and listed. In order: Start day, hour, min. sec, end day, hour, min. sec. Days relative to reference 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, 0=> all 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, 0=> all FREQID.....Frequency identifier to select. If either SELBAND or SELFREQ are set, their values overide that of FREQID. However, setting SELBAND and SELFREQ may result in an ambiguity. In that case the task will request that you use FREQID. If neither SELBAND, SELFREQ nor FREQID are specified then the first FQ id in the FQ table (usually 1) will be used. BIF........IF to list - first returned. 0 -> 1 EIF........Last IF listed and returned. 0 -> BIF+19 or max whichever is smaller. BCHAN......First channel to average. 0=> 1 When SPECTRAL > 0, channels < BCHAN are corrected but using smoothed corrections from channels BCHAN and greater. All channels are used to find solutions however. ECHAN......Last channel to average. 0=> Highest When SPECTRAL > 0, all channels are used to find solutions. However, the corrections for channels > ECHAN are determined by the solutions for channels <= ECHAN. ANTENNAS...A list of the antennas to list. If any number is negative then the antennas specified are not listed and all others are. All 0 => list all. UVRANGE....Range of projected spacings to be listed in 1000's of wavelengths. 0 => 1, 1.E10 SUBARRAY...Subarray number to list. 0=>1. 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 Cal. table to apply to the data if DOCALIB=1. Refers to a CL table for multisource data of an SN table for single source. 0 => highest. Used for OPTYPE='MATX','LIST'. 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 appply. <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. BPVER......Specifies the version of the BP table to be applied. <0 => no bandpass correction done. 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). DOINVERS...False (<= 0) => use basic solution with function ATAN True (> 0) => add 180 degrees to basic solution - this option is present for debugging purposes only. Use it with care! DOAPPLY....False (<= 0) => pass the results back to AIPS in CLCORPRM if SPECTRAL is false and display results in the message window. True (> 0) => copy the GAINUSE CL table to the highest+1 and correct the L phases (when SPECTRAL is false). Otherwise, copy the BPVER bandpass table and apply the L phases when SPECTRAL is true. SPECTRAL...False (<= 0) => average spectral channels BCHAN tthrough ECHAN and apply the solution through the CL table or CLCORPRM on an IF basis. True (> 0) => find the R-L phase difference on a channel by channel basis and, if DOAPPLY > 0, apply the result through the BP table. DOPRINT and OUTPRINT allow a text file suitable for plotting to be produced. INTPARM....After the phase corrections are determined, they may be smoothed in frequency further using the INTPARM selected function. This is to provide better S/N than one would have with unsmoothed single channels. INTPARM(1) = type of smoothing to apply: 0 => no smoothing 1 => Hanning 2 => Gaussian 3 => Boxcar 4 => Sinc (i.e. sin(x)/x) INTPARM(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 INTPARM(1) = 1 - 4. INTPARM(3) = the diameter over which the convolving function has value - in channels. Defaults: 1, 3, 1, 4 times INTPARM(2) used when input INTPARM(3) < INTPARM(2) (after application of defaults). DOPRINT....For DOLINE <= 0, the printing option is for MATX LISTR-like displays of RL and LR* phases with rmses under control: False (< 0) use the line printer if OUTPRINT = ' ' else write named OUTPRINT file only. When OUTPRINT is not blank, DOPRINT=-2 suppresses the page-feed character on page headers and DOPRINT=-3 suppresses page headers and most other header information. = 0 no printing just return answer. True (> 0) use the terminal interactively. The task will use the actual terminal width as a display limit unless 72 < DOPRINT < width. In that case, the display limit will be DOPRINT characters. For DOLINE > 0, any DOPRINT not equal 0 will cause a text file to be written to OUTPRINT if that adverb is not blank. This text file will be suitable input to PLOTR. If DOPRINT > 0, this file contains separate lists for each source and excludes channels outside BCHAN and ECHAN. If DOPRINT < 0, the smoothed and extrapolated and averaged over sources correction data are shown instead. OUTPRINT...For DOLINE <= 0, disk file name in which to save the line printer output. ' ' => use scratch and print immediately for interactive jobs - batch jobs use OUTPRINT = 'PRTFIL:BATCHjjj.nnn' (jjj= job #, nnn = user #). When OUTPRINT is not blank, multiple outputs are concatenated, and the file is not actually printed. For DOLINE > 0, if not ' ', the disk file name of a file to contain a text file which, when fed to PLOTR, can make a plot of the spectrum of the corrections. BADDISK....Disk numbers to avoid for scratch files. Scratch files may be created by the sorting routines if calibration or flagging is applied. CLCORPRM...OUTPUT adverb: X-Y phase difference in degrees for IFs BIF through BIF+19. The self-consistent mean phases so determined are returned in the adverb CLCORPRM. ----------------------------------------------------------------