; VLABP ;--------------------------------------------------------------- ;! VLA antenna beam polarization correction for snapshot images ;# TASK CALIBRATION POLARIZATION Image VLA OOP ;----------------------------------------------------------------------- ;; Copyright (C) 1995, 1999 ;; 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 ;----------------------------------------------------------------------- VLABP LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC VLABP VLA snapshot beam polarization correction Input image INNAME Image name (name), INCLASS Image class; must have 'I*', 'Q*' and 'U*'. or polarization cube INSEQ 0.0 9999.0 Image name (seq. #) INDISK 0.0 9.0 Image disk drive # ROTATE Parallactic angle (deg) Antenna fract. poln. image IN2NAME Name IN2CLASS Class, must have 'Q*' and 'U*'. IN2SEQ 0.0 9999.0 Ant. poln seq. # IN2DISK 0.0 9.0 Ant. poln drive # Corrected image OUTNAME Image name OUTCLASS Class: 'Q*' and 'U*'. OUTSEQ -1.0 9999.0 Image name (seq. #) OUTDISK 0.0 9.0 Image disk drive # BADDISK -1.0 1000.0 Disks to avoid for scratch. ---------------------------------------------------------------- VLABP Task: Corrects an VLA snapshot polarization image for the antenna residual polarization. Note this will ONLY work for snapshots as the antenna residual polarization function rotates with parallactic angle. Adverbs: INNAME......The input image name. Standard defaults. INCLASS.....The root of the input classes. The polarization images are assumed to have the same class except for the first character which is 'I', 'Q', or 'U' (e.g. 'ICL001', 'QCL001' and 'UCL001'). Default 'ICL001'. An alternative is if the input image is a polarization cube, e.g. three planes with I, Q, and U on the third axis. INSEQ.......The input map image sequence number. 0 => high INDISK......The input map image disk drive no. 0 => any ROTATE......The parallactic angle of the observations. This is used iff the Q input image does NOT have a header keyword 'PARANGLE'. If this keyword exists its associated value is used. IN2NAME.....The antenna fractional polarization image name. IN2CLASS....The root of the class name; the real and imaginary parts must be 'Q*' and 'U*' respectively (e.g. 'QFRACT', 'UFRACT'). Default 'QFRACT' IN2SEQ......The antenna polarization image sequence number. 0 => actual INSEQ IN2DISK.....The antenna polarization image disk drive no. 0 => any OUTNAME.....The output polarized image name. blank => Standard defaults based on INNAME. OUTCLASS....The root of the output image class. The real and imaginary parts will be 'Q*' and 'U*' respectively. (e.g. 'QCORR', 'UCORR') The output image may be the same as the input image. Default 'QCORR' If the input image was a polarization cube then the output will be a polarization cube in which the total intensity plane is copied from the input. OUTSEQ......The output image seq. no., 0=> highest unique If >0; image will be created if new, overwritten if image name exists. OUTDISK.....Output image disk drive no., 0=> highest with space BADDISK.....This array contains the numbers of disks on which it is desired that scratch files not be located. BADDISK has no effect on input and output maps. ---------------------------------------------------------------- VLABP: Task to correct VLA polarized snapshot images for antenna residual polarization. Documentor: W. D. Cotton NRAO Related Programs: MX This task is intended to correct VLA widefield polarization snapshot images for the effects of the residual polarization pattern of the antenna/feed. As this pattern rotates with parallactic angle this correction can only be made in the image plane for snapshots for which there is a well defined parallactic angle. The parallactic angle of the observations can either be attached to the input 'Q' image as a header keyword 'PARANGLE'. This keyword can be written ising verb PUTHEAD. An alternative is using avderb ROTATE. IN2NAME: An image of the antenna fractional polarization must be provided. This has a real ('Q') and imaginary ('U') parts which should be the ratio of the Q or U polarization to the total insensity for a source at the corresponding location. The image should correspond to parallactic angle 0 deg. This image need not be at the same cell spacing as the input image but should cover the entire region of the input images. Regions outside of this image will be blanked. Polarization cubes. The input and output image may be polarization cubes with Stokes I, Q and U on the third axis. In this case the total intensity image is copied from the input to output.