; ROBUST
;---------------------------------------------------------------
;! Uniform weighting "robustness" parameter
;# ADVERB UV IMAGING
;-----------------------------------------------------------------------
;; Copyright (C) 1995
;; 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
;-----------------------------------------------------------------------
;---------------------------------------------------------------
ROBUST LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC
----------------------------------------------------------------
ROBUST
Type: Adverb (Real)
Use: The robustness parameter, devised by Daniel Briggs, is
used to temper the effects of uniform weighting. Thus,
the weight actually used for sample i is
F1 (Wi)
WT = ----------------------
[F2 (Wj)] + S
where F1 and F2 are 2 functions applied to the input
weights (Fi (W) = W by default), the [ ] means the sum of
the F2 of the Weights of all samples in the neighborhood
of the i'th sample, and S is a function of ROBUST. We use
(10**(ROBUST)) * <[F2 (Wj)]>
S = --------------------------------
5
where < > denotes the average of the local sums over all
visibilities. Note that if ROBUST > 4, the weight sums
have little effect and the weighting is close to natural
weighting. If ROBUST < -4, then S is very small and we
have virtually pure uniform weighting with no tempering.
Null value: NONE
Tasks:
IMAGR.....Fourier transform and Clean UV data with a full
range of calibration, weighting, Cleaning, and
wide-field correction options.
----------------------------------------------------------------