; WTMOD ;--------------------------------------------------------------- ;! modifies weights in a UV data set ;# Task UV ;----------------------------------------------------------------------- ;; Copyright (C) 1995, 2001, 2004, 2006, 2014 ;; 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 ;----------------------------------------------------------------------- WTMOD LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC WTMOD Task to modify weights in a uv data set. 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 # 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 #. SUBARRAY 0.0 Limit to subarray APARM Control info: 1 = multiplier (0=>1) 2 = power (0=>1) 3 = Max. (0=>infty) ANTWT -9999.0 9999.0 Replace weights (all ants.) NOISE Scale weights by antenna FQCENTER >= 0 -> center frequency axis ---------------------------------------------------------------- WTMOD Task: This task will modify the weights of uv data as specified by the user. The purpose is to adjust the weights so that data from very sensitive baselines will not swamp the less sensitive baselines. The maximum and minimum weights (in absolute value) after the modifications will be reported. The output file may be the input file. The weights of flagged data are also modified, but they are not unflagged by this program. WTMOD can flag data, however. WTMOD can also be used to change system-temperature dependent weights into constant ones for concatenation with old data sets. WTMOD handles compressed data finally (8-Feb-2001)! It is particularly fast since it does not need to unpack and then repack the data to change the weight. 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. 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. SUBARRAY...Subarray number to which the operation should be limited. 0 -> do to all subarrays. APARM......Weight modification control information (ignored if any ANTWT is not 0.0): 1 = A multiplier for the weights. 0 => 1.0 2 = A power to which to raise the weights; 0 => 1.0 0.25 - 0.5 is a useful range for VLBI. Weight_out = (APARM(1) * Weight_in) ** APARM(2) 3 = The maximum acceptable value of the weight. Values higher that APARM(3) will be set to APARM(3). 0 => infinity. ANTWT......Replace vis. weights with constant values. A new weight must be specified for all antennas. (If there are > 30 antennas, the average (abs) value is used for antennas > 30.) Negative values may be used to flag data. Note that previously flagged data remain flagged, but otherwise at the new weights. Weight_out = SQRT (ANTWT(ant1) * ANTWT(ant2)) ignoring Weight_in except for flagging information (sign). NOISE......If all ANTWT are zero, then scale the output weights by NOISE(i) where i is the antenna number. Thus Weight_out = NOISE(ant1) * NOISE(ant2) * min (APARM(3), (APARM(1)*Weight_in) ** APARM(2)) NOISE(i) <= 0 -> NOISE(i) = 1.0 and a value of 1.0 is used for all antennas numbered greater than 64. FQCENTER...> 0 => Change frequency axis reference pixel to Nchan / 2 + 1 else => do not change reference pixel ----------------------------------------------------------------