; CLVLB ;--------------------------------------------------------------- ;! Corrects CL table gains for pointing offsets in VLBI data ;# Task Calibration VLBI ;----------------------------------------------------------------------- ;; Copyright (C) 2013 ;; 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 ;----------------------------------------------------------------------- CLVLB LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC CLVLB Corrects CL table gains for pointing offsets in VLBI data 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 # FREQID 0.0 Frequency ID number: 0 -> 1 SUBARRAY 0.0 Subarray: 0 -> 1 GAINVER Input CL table version GAINUSE Output CL table version CUTOFF -1.0 Minimum allowed beam CALIN Text file containing antenna beam parameters TT -1.0 1.0 > 0, use alternative geometry computation (Enno), else use Eric's method BIF DEBUG: print BIF when > 0 ANTENNA DEBUG: print ANTENNA(1) if >0 ---------------------------------------------------------------- TYAPL Task: DiFX correlators are capable of correlating the same input data at multiple phase stopping positions, each separated from the direction in which the antennas of array were pointed. For the tiny fields of view surrounding the antenna pointing position, the single-dish beam is essentially constant (spatially) although it will vary in time due to beam squint and other causes. This task reads an input CL table, computes the corrections in amplitude for the separate polarizations and IFs, and applies them to the CL data as a function of time. Single-dish beam patterns are notoriously hard to compute. This task assumes a simple model of them. The R polarization and L polarization beams are assumed to be each circularly symmetric and separated by equal distances in opposite directions from the pointing center. 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. FREQID.....Frequency ID number to do 0 => 1 SUBARRY....Subarray to do 0 => 1 GAINVER....Input version number of the CL table to be used. GAINUSE....Output version number of the CL table to be written. CUTOFF.....beam values < CUTOFF cause the solutions to be blanked. CALIN......Text file giving in order: 1. antenna number (0 -> a default to use for those not specified in some other way) 2. Azimuth squint (arc min (R - L) 3. Elevation squint (arc min (R - L) 4. Frequency at which 2 and 3 were measured (MHz) 5. Antenna effective diameter (meters) 6. Frequency at which 5 measured (MHz) 7. Change of effective diameter with frequency (meters/MHz) Some of these can be recorded in the ANtenna file, but usually are not. The values for VLBA antennas at L band are known by the task. In application, Azimuth squint = V(2) * V(4) / Freq(IF) Elevation squint = V(3) * V(4) / Freq(IF) D_effective = V(5) * (Freq(IF)-V(6)) * V(7) and the beam pattern is a J1(x) / x function where x = pi * D_effective / lambda * sin(offset) Some of these must be given to have the task work. DEBUG option TT.........In order to find the primary beam level, Eric's algorithm adds the squints to the pointing position (linearly) and then computes the separation of the 2 squinted positions and the target (fully non-linearly). TT <= 0.0 Enno's finds the separation and angle from the pointing position to the target (fully non-linearly) and then adds the squint parameters (linearly) before finding the separation (also linearly). TT > 0.0 BIF........If > 0, then do debug print out with IF = BIF ANTENNA....If ANTENNA(1) > 0, then do debug print out with ANTENNA(1) and BIF only. The debug print out shows antenna #, polarization, time number, elevation (degrees), azimuth (degrees), separation (degrees), and beam power factor. ----------------------------------------------------------------