; FRING ;--------------------------------------------------------------- ;! fringe fit data to determine antenna calibration, delay, rate ;# TASK CALIBRATION AP VLBI ;----------------------------------------------------------------------- ;; Copyright (C) 1995-2004, 2006, 2009 ;; 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 ;----------------------------------------------------------------------- FRING LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC FRING: Task to fringe fit data Input uv data. INNAME UV file name (name) INCLASS UV file name (class) INSEQ 0.0 9999.0 UV file name (seq. #) INDISK 0.0 9.0 UV file disk drive # Data selection (multisource): CALSOUR Calibrator sources QUAL -10.0 Calibrator qualifier -1=>all CALCODE Calibrator code ' '=>all SELBAND Bandwidth to select (kHz) SELFREQ Frequency to select (MHz) FREQID Freq. ID to select. TIMERANG Time range to use. BCHAN 0.0 2048.0 Lowest channel number 0=>all ECHAN 0.0 2048.0 Highest channel number ANTENNAS Antennas to select. 0=all DOFIT Subset of ANTENNAS list for which solns are desired. SUBARRAY 0.0 1000.0 Subarray, 0=>all UVRANGE Range of uv distance for full weight WTUV Weight outside UVRANGE 0=0. WEIGHTIT 0.0 3.0 Modify data weights function Cal. info for input: DOCALIB -1.0 101.0 > 0 calibrate data & weights > 99 do NOT calibrate weights GAINUSE CL table to apply. DOPOL -1.0 10.0 If >0 correct polarization. BLVER BL table to apply. FLAGVER Flag table version DOBAND -1.0 10.0 If >0 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. CLEAN map (optional) IN2NAME Cleaned map name (name) IN2CLASS Cleaned map name (class) IN2SEQ 0.0 9999.0 Cleaned map name (seq. #) IN2DISK 0.0 9.0 Cleaned map disk unit # INVERS -1.0 46655.0 CC file version #. NCOMP # comps to use for model. 1 value per field FLUX Lowest CC component used. NMAPS 0.0 4096.0 No. Clean map files CMETHOD Modeling method: 'DFT','GRID',' ' CMODEL Model type: 'COMP','IMAG' 'SUBI' (see HELP re images) SMODEL Source model, 1=flux,2=x,3=y See HELP SMODEL for models. Output uv data file. OUTNAME UV file name (name) OUTCLASS UV file name (class) OUTSEQ -1.0 9999.0 UV file name (seq. #) OUTDISK 0.0 9.0 UV file disk drive # Solution control adverbs: REFANT Reference antenna SEARCH 0.0 1000.0 Prioritized reference antenna list - supplements REFANT - but only if APARM(9)>0 SOLINT Solution interval (min) 0 => 10 min SOLSUB Solution subinterval SOLMIN Min solution interval APARM General parameters 1=min. no. antennas 2 > 0 => data divided 3 > 0 => avg. RR,LL 4 > 0 => avg. freq. in IFs 5 > 0 => combine IFs. 6=print level, 1=some 7=SNR cutoff (0=>5) 8=max. ant. # (no AN) 9 > 0 => do exhaustive baseline search DPARM Delay-rate parameters 1=no. bl combo. (def=3) 2=delay win (nsec), if <0 no delay search done 3=rate win (mHz) 4=int. time (sec) 0 => min. found in data 5 >0 => don't do ls. soln 6 >0 => don't avg. in freq 7 >0 => don't rereference phase 8 > 0 => activate zero'ing options 9 > 0 => do not fit rate SNVER -1.0 46655.0 Output SN table, 0=>new table ANTWT Ant. weights (0=>1.0) BADDISK 0.0 15.0 Disk no. not to use for scratch files. ---------------------------------------------------------------- FRING Task: This task determines the group delay and phase rate calibration to be applied to a uv data set given a model of the source(s). The output data will have the corrections applied for a single source input file; and a solution (SN) table will be left for a multi source data set. SN tables will be attached to the INPUT data file. Model images made with both values of IMAGR's DO3DIMAG option are handled correctly, as are multi-scale images. Set NMAPS = NFIELD * NGAUSS. FRING now uses dynamic memory throughout, allowing large delay-rate searches no matter what size the pseudo AP may be. Of course, your computer must have enough memory to support this allocation. 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. The following are used for multisource data files only: CALSOUR....List of sources for which calibration constants are to be determined, i.e. the calibrator sources All ' ' = all sources; a "-" before a source name. means all except ANY source named. Note: solutions for multiple sources can only be made if the sources are point sources at their assumed phase center and with the flux densities given in the source (SU) table. QUAL.......Only sources with a source qualifier number in the SU table matching QUAL will be used if QUAL is not -1. CALCODE....Calibrators may be selected on the basis of the calibrator code: ' ' => any calibrator code selected '* ' => any non blank code (cal. only) '-CAL' => blank codes only (no calibrators) anything else = calibrator code to select. NB: The CALCODE test is applied in addition to the other tests, i.e. CALSOUR and QUAL, in the selection of sources for which to determine solutions. 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, 0=> all 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, 0=> all 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 which case the task will request that you use FREQID. TIMERANG...Time range of the data to be used. In order: Start day, hour, min. sec, end day, hour, min. sec. Days relative to reference date. BCHAN......First channel to use. 0=>all. ECHAN......Highest channel to use. 0=>all higher than BCHAN ANTENNAS...A list of the antennas to have solutions determined. If any number is negative then all antennas listed are NOT to be used to determine solutions and all others are. All 0 => use all. DOFIT......A list of the antennas for which solutions should or should not be determined. If DOFIT = 0, all antennas are solved for. If any entry <= -1, , then DOFIT is taken as the list of antennas for which no solution is desired; a solution is found for all antennas not in DOFIT. If any entry of DOFIT is non-zero and all are >= 0, then only those antennas listed in DOFIT will be solved for - all other selected antennas will not be solved for. NOTE: THIS OPTION MUST NOT BE USED UNLESS YOU UNDERSTAND IT FULLY. Basically, it should be used to solve for the gains of "poor" antennas after the "good" antennas have been fully calibrated. Antennas included in ANTENNAS but not in DOFIT are assumed to have a complex gain/delay/rate of (1,0,0,0) and the gains/delays produced will be very wrong if this is not the case. See HELP DOFIT. The following may be used for all data files (except as noted): SUBARRAY...Subarray number to use. 0=>all. UVRANGE....The range of uv distance from the origin in kilowavelengths over which the data will have full weight; outside of this annulus in the uv plane the data will be down weighted by a factor of WTUV. WTUV.......The weighting factor for data outside of the uv range defined by UVRANGE. WEIGHTIT...If > 0, change the data weights by a function of the weights just before doing the solution. Choices are: 0 - no change weighting by 1/sigma**2 1 - sqrt (wt) weighting by 1/sigma may be more stable 2 - (wt)**0.25 3 - change all weights to 1.0 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). Done before determining solutions. GAINUSE....(multisource) version number of the CL table to apply to the data. 0 => highest. DOPOL......If > 0 then correct data for instrumental polarization as represented in the AN table. Only one subarray may be done at a time. 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. BLVER......Version number of the baseline based calibration (BL) table to appply. <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.....(multi-source) 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. BPVER......(multi-source) version of the BP table to be applied. 0 => highest; < 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). The following specify a CLEAN model to be used if a single source was specified in CALSOUR: IN2NAME....Cleaned map name (name). Standard defaults. Note: a CLEAN image for only a single-source may be given although it may be in a multi-source file. If the source table contains a flux, then that flux will be used to scale the components model to obtain the stated total flux. This is needed since initial Cleans may not obtain the full flux even though they represent all the essentials of the source structure. IN2CLASS...Cleaned map name (class). Standard defaults. IN2SEQ.....Cleaned map name (seq. #). 0 -> highest. IN2DISK....Disk drive # of cleaned map. 0 => any. INVERS.....CC file version #. 0=> highest numbered version NCOMP......Number of Clean components to use for the model, one value per field. If all values are zero, then all components in all fields are used. If any value is not zero, then abs(NCOMP(i)) (or fewer depending on FLUX and negativity) components are used for field i, even if NCOMP(i) is zero. If any of the NCOMP is less than 0, then components are only used in each field i up to abs(NCOMP(i)), FLUX, or the first negative whichever comes first. If abs(NCOMP(i)) is greater than the number of components in field i, the actual number is used. For example NCOMP = -1,0 says to use one component from field one unless it is negative or < FLUX and no components from any other field. This would usually not be desirable. NCOMP = -1000000 says to use all components from each field up to the first negative in that field. NCOMP = -200 100 23 0 300 5 says to use no more than 200 components from field 1, 100 from field 2, 23 from field 3, 300 from field 5, 5 from field 6 and none from any other field. Fewer are used if a negative is encountered or the components go below FLUX. FLUX.......Only components > FLUX in absolute value are used in the model. NMAPS......Number of image files to use for model. For multi-scale models, set NMAPS = NFIELD * NGAUSS to include the Clean components of the extended resolutions. If more than one file is to be used, the NAME, CLASS, DISK and SEQ of the subsequent image files will be the same as the first file except that the LAST 3 or 4 characters of the CLASS will be an increasing sequence above that in IN2CLASS. Thus, if INCLASS='ICL005', classes 'ICL005' through 'ICLnnn' or 'ICnnnn', where nnn = 5 + NMAPS - 1 will be used. Old names (in which the 4'th character is not a number) are also supported: the last two characters are '01' through 'E7' for fields 2 through 512. In old names, the highest field number allowed is 512; in new names it is 4096. CMETHOD....This determines the method used to compute the model visibility values. 'DFT' uses the direct Fourier transform, this method is the most accurate. 'GRID' does a gridded-FFT interpolation model computation ' ' allows the program to use the fastest method CMODEL.....This indicates the type of input model; 'COMP' means that the input model consists of Clean components, 'IMAG' indicates that the input model consists of images. 'SUBI' means that the model consists of a sub-image of the original IMAGR output. If CMODEL is ' ' Clean components will be used if present and the image if not. SUBI should work for sub-images made with DO3DIM true and sib-images of the central facet made with DO3DIM false, but probably will not work well for shifted facets with DO3DIM false. Use BLANK rather than SUBIM in such cases. CALIB will set a scaling factor to correct image units from JY/BEAM to JY/PIXEL for image models. If the source table contains a flux, then that flux will be used to scale the components model to obtain the stated total flux. This is needed since initial Cleans may not obtain the full flux even though they represent all the essentials of the source structure. SMODEL.....A single component model to be used instead of a CLEAN components model; if abs (SMODEL) > 0 then use of this model is requested. SMODEL(1) = flux density (Jy) SMODEL(2) = X offset in sky (arcsec) SMODEL(3) = Y offset in sky (arcsec) SMODEL(4) = Model type: 0 => point model 1 => elliptical Gaussian and SMODEL(5) = major axis size (arcsec) SMODEL(6) = minor axis size (arcsec) SMODEL(7) = P. A. of major axis (degrees) 2 => uniform sphere and SMODEL(5) = radius (arcsec) The following specify the output file to be written if the input file is a single source file. 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 disk number with space The following control how the solutions are done, if you don't understand what a parameter means leave it 0 and you will probably get what you want. REFANT.....The desired reference antenna for phases. SEARCH.....List of Prioritized antennas to be used when APARM(9)>0. This adverb supplements REFANT. Along with APARM(9)>0, it is recommended that SEARCH be filled with a list of antennas whose order reflects the user's notion of which baselines will be easiest to find fringes on. All baselines to each antenna in SEARCH will be searched in order looking for fringes. All remaining baselines will then be searched. Choosing SEARCH wisely will speed the FFT portion of FRING. The antenna chosen in REFANT is treated as SEARCH(0), ie all baselines to it are searched first. SOLINT.....The solution interval (min.) You really should set this; longer values are allowed beginning with 15OCT96. 0 => 10 minutes for all inputs If SOLINT > Scan/2 (in Multisource) SOLINT = Scan. SOLSUB.....The begin time for the next interval in advanced from the current one by SOLINT / SOLSUB where 1 <= SOLSUB <= 10. 0 -> 1. This is to produce solutions at sub-intervals of SOLINT based on SOLINT length of averaging. SOLMIN.....Minimum number of subintervals to be used in a solution. 0 -> SOLSUB. APARM......General control parameters. APARM(1)...Minimum number of antennas allowed for a solution. 0 => 3. APARM(2)...If > 0 then the input data has already been divided by a model; only solutions will be determined. APARM(3)...If > 0 then average RR, LL APARM(4)...If > 0 average all frequencies in each IF before the solution and in the output for single source files. APARM(5)...If > 0 then make a combined solution for the IFs; if <= 0 then make separate solutions. If > 1.5 do separate least squares fits for single- and multi-band delays. This option will override APARM(4) > 0. WARNING: multi-band delays derived by this method cannot be smoothed. APARM(6)...Print flag, -1=none, 0=time every 10th time, 1=time,some info, 2=more including the antenna signal to noise ratio, 3=a very great deal. APARM(7)...The minimum allowed signal-to-noise ratio. 0 => 5 APARM(8)...If there is no antenna (AN) table with the input file then the maximum antenna number in the file should be entered in APARM(8). APARM(9)...If > 0, perform exhaustive baseline search in the initial FFT stage. Normally, the first stage of FRING is to FFT individual baselines searching for initial estimates of the residual phases, rates, and delays. This stage is notable in that FRING gives up too easily - only baselines to the user-selected REFANT and one other antenna are searched. APARM(9)>0 instructs FRING to exhaustively search for initial estimates for each antenna's errors. See SEARCH above as well. Delay-rate control parameters: DPARM......Delay rate parameters. DPARM(1)...Number of baseline combinations to use in the initial, coarse fringe search (1-3). Larger values increase the point source sensitivity but reduce the sensitivity to extended sources when an accurate model is not available. 0=>3. DPARM(2)...The delay window to search (nsec) centered on 0 delay. 0 => full Nyquist range defined by the frequency spacing. If DPARM(2) < 0.0 no delay search will be performed. DPARM(3)...The rate window to search (mHz) centered on 0 rate. 0 => full Nyquist range defined by the integration time. DPARM(4)...The minimum integration time of the data (sec); 0 => search the data to find the minimum integration time. The correct minimum of all baselines should be supplied. DPARM(5)...If > 0 then don't do the least squares solution. If the least squares solution is not done then only the coarse search is done and much less accurate solutions are obtained. DPARM(6)...If > 0 then the output data will not be averaged in frequency else, all frequencies in each IF will be averaged. Affects single source files only. DPARM(7)...If > 0 then the phase, rate and delays will not be re-referenced to a common antenna. This option is only desirable for VLBI polarization data. DPARM(8)...DPARM(8)>0 allows zero'ing of RATE, DELAY, and/or PHASE solutions. ** Note that the ZEROing is done _AFTER_ the FRING solution is found, this is not the mechanism for turning off the DELAY, RATE, or PHASE search, see DPARM(2-3) for that capability. ** DPARM(8) value zero RATES? zero DELAYs? zero PHASEs? 0 No No No 1 Yes No No 2 No Yes No 3 Yes Yes No 4 No No Yes 5 Yes No Yes 6 No Yes Yes 7 Yes Yes Yes DPARM(9)...> 0 => supress fitting for rate (rather than just zero the fit afterwards). This assumes that the true rate is small and causes all the data in SOLINT to be averaged before being fed to the fitter. DPARM(8)=1 is not needed in this case. SNVER......Desired output SN table. Solutions will be added to the specified table replacing any previous solutions for the same TIMERANG, CALSOUR etc. 0 means create a new SN table. ANTWT......Antenna weights. These are additional weights to be applied to the data before doing the solutions, one per antenna. Use PRTAN to determine which antenna numbers correspond to which antennas. BADDISK....A list of disk numbers to be avoided when creating scratch files. ---------------------------------------------------------------- For some basic introduction to fringe fitting, please see the discussions in: Thompson, Moran, and Swenson Felli and Spencer Perley, Schwab, and Bridle The AIPS cookbook also describes how and when FRING should be used.