; SDVEL ;--------------------------------------------------------------- ;! shifts spectral-line single-dish data to a given velocity ;# TASK SPECTRAL CALIBRATION SINGLEDISH UV ;----------------------------------------------------------------------- ;; Copyright (C) 1997-1998 ;; Associated Universities, Inc. Washington DC, USA. ;; Eric W. Greisen ;; ;; 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 ;----------------------------------------------------------------------- SDVEL LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC SDVEL Task to shift spectral-line data to a given velocity 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 0.0 9999.0 Output UV file name (seq. #) OUTDISK 0.0 9.0 Output UV file disk unit # FLAGVER Flag table version TIMERANG Time range to include DPARM Compute and debug controls (1) 0 -> velocity set at 1st record of each scan 1 -> velocity set at last record of each scan 2 -> velocity set at last record of each scan preceeding an OFF 3 -> velocity set at 1st record of data set (2) 0 -> use ref. coordinate 1 -> use coordinate of record 2 -> use coordinate in COORDINA (3) Issue warning if shift > DPARM(3) channels. (4) Flag if shift > DPARM(4) channels. 0 -> Nchan COORDINA Velocity reference RA/dec BADDISK 0.0 9999.0 Disks to avoid for scratch ---------------------------------------------------------------- SDVEL Task: Shift a single-dish uv spectral-line data set in frequency space. The purpose of the task is to shift all spectra to a given velocity for the directions of observation. This task assumes that the telescope has tracked - at some interval - the time variation of frequency to maintain an approximately constant velocity for the reference coordinate. It then shifts each spectrum so that the reference velocity wrt the actual observed coordinate is in the reference channel. This is a subtle effect, previously ignored in spectral-line imaging. However, for a coordinate 1.4 degrees from the reference (e.g., a 2 degree square field with a center reference), the error can be as large as 1.16 km/sec (LSR velocities) or 0.79 km/sec (heliocentric) observed with NRAO's 12m telescope. Both vary with time, reference coordinate, and telescope; the LSR velocity error changes significantly with time of year. Narrow-band observations of wide fields, such as observations of cold molecular regions, may be seriously affected by this effect. Fortunately, so long as the spectra are fully sampled in frequency, this effect can be fully corrected in single-dish data. interferometer users are not so lucky. 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. OUTDISK....Drive # of output UV file. 0 => highest with space for the file. FLAGVER....specifies the version of the flagging table to be applied. 0 => highest numbered table. <0 => no flagging to be applied. TIMERANG...Time range to include: start day, hour, minute, second, end day, hour, minute, second. end = 0 -> infinity. DPARM......Controls: (1) Tells the task when to compute the reference doppler shift as 0 -> at the starting record of EACH scan 1 -> after each scan using the last time of the scan but applying it to the next scan 2 -> on each "off" scan (detected by a missing scan number) using the last coordinate before the off. 3 -> at the first record of the data set. The 12m probably now uses mode 0, it used to use mode 2. (2) Tells the task what coordinate to use in the Doppler computation as 0 -> data set reference coordinate 1 -> coordinate of the particular record 2 -> user specified coordinate in COORDINA The 12m used to use mode 1, now uses mode 0, but can use mode 2. (3) A warning is issued if the shift exceeds DPARM(3) channels. 0 -> NCHAN/20. The task limits the number of consecutive samples warned to 10 but if there are then good samples, it will resume warnings on the next "bad". (4) A sample is deleted if the shift exceeds DPARM(4) channels. 0 -> NCHAN. This may be used to detect and flag periods in which the antenna is blown way off course . COORDINA...The RA and declination coordinates are found as: RA = abs(CO(1)) + abs(CO(2))/60 + abs(CO(3))/3600 if any of CO(1), CO(2), CO(3) < 0: Xpos = -Xpos Dec = abs(CO(4)) + abs(CO(5))/60 + abs(CO(6))/3600 if any of CO(4), CO(5), CO(6) < 0: Ypos = -Ypos The units are standard FITS units (e.g degrees) except that right ascensions are in hours of time. BADDISK....A list of disks on which scratch files are not to be placed. This will not affect the output file. ----------------------------------------------------------------