; AVSPC ;--------------------------------------------------------------- ;! Averages uv-data in the frequency domain ;# Task UV Spectral ;----------------------------------------------------------------------- ;; Copyright (C) 1995, 2000-2001, 2004, 2007, 2010-2011 ;; 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 ;----------------------------------------------------------------------- AVSPC LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC AVSPC Task to average uv data in frequency. 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 # SOURCES Source name QUAL -10.0 Calibrator qualifier -1=>all CALCODE Calibrator code ' '=>all STOKES Stokes of output TIMERANG Time range to use SELBAND Bandwidth to select (kHz) SELFREQ Frequency to select (MHz) FREQID Freq. ID to select. SUBARRAY 0.0 1000.0 Sub-array, 0=>all BIF Low IF number to do EIF Highest IF number to do DOCALIB -1.0 101.0 > 0 calibrate data & weights > 99 do NOT calibrate weights GAINUSE CL (or SN) table to apply DOPOL -1.0 10.0 If >0.5 correct polarization. PDVER PD table to apply (DOPOL>0) BLVER BL table to apply. FLAGVER Flag table version DOBAND -1.0 10.0 If >0.5 apply bandpass cal. Method used depends on value of DOBAND (see HELP file). BPVER Bandpass table version SMOOTH Smoothing function. See HELP SMOOTH for details. DOACOR Include autocorrelations? 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 #. ICHANSEL Array of start and stop chn numbers, plus a channel increment and IF to be used for channel selection in the averaging. See HELP ICHANSEL. Default = center 75% of band. AVOPTION Averaging option ' ','SUBS' SUBS ignores ICHANSEL. CHANNEL # chans to average together used when AVOPTION = 'SUBS' ---------------------------------------------------------------- AVSPC Task: Average a uv database in the frequency domain. The two principal uses of this task are to create a data base containing 'continuum' channels for use in calibrating spectral line observations and for averaging in frequency for continuum observations that don't require frequency resolution to reduce bandwidth smearing. For the purpose of forming a continuum data base from spectral line observations AVSPC has optional channel selection so channels may be omitted from the average if necessary. The default channel range that is averaged is the center 75%, this is what is used at the VLA to produce 'channel 0'. Note that there are other tasks for forming channel 0 data sets and for frequency averaging including averaging over IFs. These include SPLIT and SPLAT, UVLSF which fits a linear continuum to a (possibly shifted) spectrum, and SPECR which uses Fourier transform methods to increase or decrease the number of spectral channels. 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. SOURCES....Source to be included. ' '=> all; if any starts with a '-' then all except ANY source named. QUAL.......Qualifier of source to be included. -1 => all. CALCODE....Calibrator code of sources to include. ' '=> all. STOKES.....Specifies which STOKES parameters are written in the output data set: ' ' => 'FULL' 'I','Q','U','V', 'IV', 'IQU', 'IQUV' 'RR','LL', 'RL', 'LR', 'RRLL', 'RLLR', 'RLRL' 'XX','YY', 'XY', 'YX', 'XXYY', 'XYYX', 'XYXY' 'HALF', 'CROS', and 'FULL' have sensible interpretations depending on the Stokes present in the data. The last in each of the 3 rows above == 'FULL'. Note that many combinations of polarizations in the input and values above are not supported. TIMERANG...Time range of the data to be copied. In order: Start day, hour, min. sec, end day, hour, min. sec. Days relative to ref. date. SELBAND....Bandwidth of data to be selected. If more than one IF is present SELBAND is the width of the first IF required. Units = kHz. For data which contain multiple bandwidths/frequencies the task will insist that some form of selection be made by frequency or bandwidth. SELFREQ....Frequency of data to be selected. If more than one IF is present SELFREQ is the frequency of the first IF required. Units = MHz. FREQID.....Frequency identifier to select (you may determine which is applicable from the OPTYPE='SCAN' listing produced by LISTR). If either SELBAND or SELFREQ are set, their values override that of FREQID. However, setting SELBAND and SELFREQ may result in an ambiguity. In that case, the task will request that you use FREQID. SUBARRAY...Sub-array number to copy. 0=>all. BIF........First IF to include. 0 -> 1. EIF........Last IF to include. 0 -> max. Channel selection is done with ICHANSEL. DOCALIB....If true (>0), calibrate the data using information in the specified Cal (CL) table for multi-source or SN table for single-source data. Also calibrate the weights unless DOCALIB > 99 (use this for old non-physical weights). GAINUSE....version number of the CL table to apply to multi-source files or the SN table for single-source files. 0 => highest. DOPOL......If > 0 then correct data for instrumental polarization as represented in the AN or PD table. This correction is only useful if PCAL has been run or feed polarization parameters have been otherwise obtained. See HELP DOPOL for available correction modes: 1 is normal, 2 and 3 are for VLBI. 1-3 use a PD table if available; 6, 7, 8 are the same but use the AN (continuum solution) even if a PD table is present. PDVER......PD table to apply if PCAL was run with SPECTRAL true and 0 < DOPOL < 6. <= 0 => highest. BLVER......Version number of the baseline based calibration (BL) table to apply. <0 => apply no BL table, 0 => highest. FLAGVER....specifies the version of the flagging table to be applied. 0 => highest numbered table. <0 => no flagging to be applied. DOBAND.....If true (>0) then correct the data for the shape of the antenna bandpasses using the BP table specified by BPVER. The correction has five modes: (a) if DOBAND=1 all entries for an antenna in the table are averaged together before correcting the data. (b) if DOBAND=2 the entry nearest in time (including solution weights) is used to correct the data. (c) if DOBAND=3 the table entries are interpolated in time (using solution weights) and the data are then corrected. (d) if DOBAND=4 the entry nearest in time (ignoring solution weights) is used to correct the data. (e) if DOBAND=5 the table entries are interpolated in time (ignoring solution weights) and the data are then corrected. IMAGR uses DOBAND as the nearest integer; 0.1 is therefore "false". BPVER......Specifies the version of the BP table to be applied 0 => highest numbered table. <0 => no bandpass correction to be applied. SMOOTH.....Specifies the type of spectral smoothing to be applied to a uv database . The default is not to apply any smoothing. The elements of SMOOTH are as follows: SMOOTH(1) = type of smoothing to apply: 0 => no smoothing To smooth before applying bandpass calibration 1 => Hanning, 2 => Gaussian, 3 => Boxcar, 4 => Sinc To smooth after applying bandpass calibration 5 => Hanning, 6 => Gaussian, 7 => Boxcar, 8 => Sinc SMOOTH(2) = the "diameter" of the function, i.e. width between first nulls of Hanning triangle and sinc function, FWHM of Gaussian, width of Boxcar. Defaults (if < 0.1) are 4, 2, 2 and 3 channels for SMOOTH(1) = 1 - 4 and 5 - 8, resp. SMOOTH(3) = the diameter over which the convolving function has value - in channels. Defaults: 1,3,1,4 times SMOOTH(2) used when input SMOOTH(3) < net SMOOTH(2). DOACOR.....> 0 => include autocorrelations as well as cross correlation data. 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. ICHANSEL...Array of start and stop channels plus a channel increment and IF, used to select the channels to be averaged. For instance, if you wished to exclude channels 1 - 10 and 121 - 128 because of bandpass effects, and channels 56 - 80 of IF 1 but not IF 2 because of interference, then you would set ICHANSEL = 11,55,1,1, 81,121,1,1, 11,121,1,2. If you only wished to use every other channel from the second IF then you would set ICHANSEL = 11,55,1,1, 81,121,1,1, 11,121,2,2. Up to 20 groups of start, stop and increment channel numbers plus IF numbers can be specified. The default (ICHANSEL = 0) is to average the center 75% of the band, i.e. ICHANSEL(1,1) = (# channels)/8 + 1 For example: # channels=16 => ICHANSEL(1,1)=3 ICHANSEL(2,1) = (# channels + 1)*7/8 For example: # channels=16 => ICHANSEL(2,1)=14 ICHANSEL(3,1) = 1 ICHANSEL(4,1) = 0 (meaning all IFs). If ICHANSEL describes averaging explicitly for some IFs, but skips other IFs, then the center 75% of the band is averaged for the skipped IFs. For example: ICHANSEL=2,6,1,2 => The channels 2-6 will be averaged for IF=2 and the center 75% of the band will be averaged for the rest of the IFs. AVOPTION...The averaging option. ' ' means only average frequency channels for each IF separately under control of ICHANSEL. 'SUBS' means average every n channels of each IF together ignoring ICHANSEL producing an output file of spectral size INT(input/n). Any excess channels from the input spectrum will be discarded. The number of channels to average together is specified by CHANNEL. E.g. AVOPTION = 'SUBS', CHANNEL = 8 on a 128 channel input file will produce 16 channels in the output file. The ICHANSEL adverb is ignored when AVOPTION = 'SUBS' A boxcar average will be done of those channels to be averaged together. CHANNEL....The number of channels/IF to average together when AVOPTION = 'SUBS'. i.e., channel = # input channels / # output channels ----------------------------------------------------------------