; VLBAFPOL ;--------------------------------------------------------------- ;! Checks and corrects polarization labels for VLBA data ;# PROCEDURE VLBI UTILITY ;----------------------------------------------------------------------- ;; Copyright (C) 2000; 2006 ;; 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 ;----------------------------------------------------------------------- ;--------------------------------------------------------------- VLBAFPOL LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC VLBAFPOL: Procedure to check polarization labels INNAME Input file name INCLASS Input file class INSEQ Input file sequence number INDISK Disk number for input file OUTDISK Disk number for output file (this disk must have enough free space to hold a copy of the input file). VLBAFPOL is defined in the VLBAUTIL run file. ---------------------------------------------------------------- VLBAFPOL Type: Procedure Use: VLBAFPOL is a procedure that checks the polarization labels for VLBA data and either creates a new file that is labeled correctly or recommends a course of action. Type RUN VLBAUTIL to make the VLBAFPOL procedure available. INNAME.....The name of the file to be checked. Wildcard characters are allowed. INCLASS....The class of the file to be checked. Wildcard characters are allowed. INSEQ......The sequence number of the file to be checked. Zero defaults to the highest sequence number of a file matching INNAME, INCLASS, and INDISK. INDISK.....The disk drive number of the file to be checked. Zero defaults to any disk. OUTDISK....The disk drive number of a disk to hold the corrected data. This disk must have sufficient free space to hold a copy of the input file. Zero defaults to any disk. ---------------------------------------------------------------- VLBAFPOL: Procedure to check VLBA polarizations Documentor: Chris Flatters Related Programs: VLBAUTIL, FXPOL WHEN TO USE VLBAFPOL Use VLBAFPOL to check whether you need to relabel the polarizations in your data after loading the data, looking for subarrays, and merging redundant calibration data but before reading any calibration data from non-VLBA stations. VLBAFPOL assumes that all of your FREQIDs have similar polarization setups. For this reason, you should normally run VLBAFPOL after copying each frequency ID to a separate file. This may be done using VLBAFQS. This strategy also reduces the amount of disk space needed for VLBAFPOL. You should make sure that at least one disk has enough free space to hold a copy of your data before running VLBAFPOL. VLBAFPOL is intended for novice and experienced VLBA users. WHAT VLBAFPOL WILL DO VLBAFPOL will inspect your data to see if it appears to be a dual-polarization data set labelled as having a single polarization. It does this by checking the number of polarizations in the header and by checking the frequency (FQ) table for IFs with the same frequency. There are a number of possible outcomes. * VLBAFPOL will do nothing because the header claims that the data already have more than one polarization. * VLBAFPOL will do nothing because no two IFs have the same frequency and VLBAFPOL concludes that there is only one polarization present. This conclusion is incorrect if you have used an unusual set-up with different polarizations at different frequencies; if this is the case you may wish to run FXPOL manually to fix the labelling. You may also wish to run FXPOL manually to change the polarization labels from RR to LL or vice versa. * VLBAFPOL will run FXPOL automatically because the IFs are all paired in frequency. There is a small chance that VLBAFPOL will determine the output polarizations incorrectly. If this happens then you will need to run FXPOL by hand. * VLBAFPOL will no nothing because some but not all IFs are paired. This indicates that there is more than one polarization present but VLBAFPOL can not guess how the polarizations should be mapped to IFs. In this case you need to run FXPOL manually.