; SDLSF ;--------------------------------------------------------------- ;! least squares fit to channels and subtracts from SD uv data ;# TASK UV SPECTRAL EDITING SINGLEDISH ;----------------------------------------------------------------------- ;; Copyright (C) 1996-1997, 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 ;----------------------------------------------------------------------- SDLSF LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC SDLSF Least squares fit baseline and subtracts from SD 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 # 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 #. CHANSEL Select channels to fit: NOTE this is start,end,increment for each region ORDER 0.0 1.0 Order of the baseline (0/1) DOALL -1.0 1.0 > 0 => fit the average of all spectra at a given time. DOOUTPUT -1.0 1.0 > 0 => write fit baseline as a continuum uv data base CHANNEL 0.0 9999.0 Channel of fit to be written as continuum: 0 -> reference FLUX 0.0 Flag data if residual flux in any fit channel is > FLUX 0 -> 10**20 CUTOFF 0.0 Flag data if RMS of residual in fit channels > CUTOFF 0 -> 10**20 PRTLEV 0.0 Print summary of data flagged > 0 => detail by channel ---------------------------------------------------------------- SDLSF Task: This task does a spectral baseline subtraction. It fits a straight line (with optional slope) to a set of selected spectral channels using either each observation individually or the average of all observations at a given time. It then subtracts the fitted baseline from each spectrum used in the average. Optionally, it can flag data having excess residuals in the channels used for the baseline fitting. This is a good method for detecting and deleting data damaged by RFI. The whole process is useful for producing better initial data for the imaging operations and may well eliminate the need for baseline removal from the images (TRANS-IMLIN-TRANS). (If SDLSF is used to remove the "weather" (estimated from the average of multiple feeds pointing in different directions at any given time), then some spectral baseline may well remain after the initial SDIMG.) Adverbs: INNAME.....Input (SD) UV file name (name). Standard defaults. INCLASS....Input (SD) UV file name (class). Standard defaults. INSEQ......Input (SD) UV file name (seq. #). 0 => highest. INDISK.....Disk drive # of input (SD) UV file. 0 => any. OUTNAME....Output (SD) UV file name (name). Standard defaults. OUTCLASS...Output (SD) UV file name (class). Standard defaults. OUTSEQ.....Output (SD) UV file name (seq. #). 0 => highest unique OUTDISK....Disk drive # of output (SD) UV file. 0 => highest with space for the file. CHANSEL....Select up to 10 groups of channels to fit as sets of (Start,end,inc), i.e., CHANSEL = 6,37,1, 92,123,1 Defaults: if CHANSEL(1,1) and CHANSEL(2,1) are <= 0, use all channels. Else use CHANSELs until CHANSEL(1,i) and CHANSEL(2,i) are both <= 0 ignoring ones >= i. CHANSEL(1,j) defaults to 1, CHANSEL(2,j) < CHANSEL(1,j) defaults to Nchan. CHANSEL(3,j) < 1 or > CHANSEL(2,j) - CHANSEL(1,j) + 1 defaults to 1. ORDER......Order of the baseline: 0 no slope, 1 a slope is also fit. NCOUNT=1 is highly recommended unless the data are very noisy and only a few channels available for the baseline fit. DOALL......> 0 => fit the average of all observations occuring at the same time (and consecutively in the data set). <= 0 => fit each observation individually. If there is a single pointing position at a given time, DOALL TRUE will get the average baseline for, for example, the two polarizations at that time with somewhat greater reliability than it would fitting the two individually. For multiple pointing positions at a single time (e.g., the 8-beam system), DOALL TRUE obtains the average baseline for several positions at once. This may be a good measure of the "weather" at that time but may not be such a good measure of the baselines at each of the 8 positions (especially if one or more of the feeds has instrumental offsets or other problems). If you use DOALL TRUE with multi-feed data, you may anticipate the need for additional baseline removal after the images are made. DOOUTPUT...<= 0 => write out only the subtracted uv data. > 0 => write also a data set with the fit baseline as a single-channel (SD) UV data set. CHANNEL....When DOOUTPUT > 0, write the continuum data with the fit evaluated at spectral channel CHANNEL. 0 => reference channel. FLUX.......If the residual flux in any channel used to fit the baseline exceeds FLUX, then the spectrum for that time, IF, and polarization is fully flagged. <= 0 => 1.0E20 CUTOFF.....If the RMS flux in the channels used to fit the baseline exceeds CUTOFF, then the spectrum for that time, IF, and polarization is fully flagged. <= 0 => 1.0E20 PRTLEV.....A summary of points flagged is printed. To print (in the message file) any channel having >= PRTLEV samples flagged for excess residuals, set PRTLEV > 0. = 0 => print only the totals. ----------------------------------------------------------------