; FRMAP ;--------------------------------------------------------------- ;! Task to build a map using fringe rate spectra ;# TASK Spectral Astrometry Coordinates UV VLA VLBI ;----------------------------------------------------------------------- ;; Copyright (C) 1995-1998, 2000, 2003, 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 ;----------------------------------------------------------------------- FRMAP LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC FRMAP Task to build a map using fringe rate spectra USERID User number - ignored 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 list; The first one is mapped; if blank => the first one in the data. QUAL -10.0 Source qualifier -1=>all CALCODE Calibrator code ' '=>all SELBAND Bandwidth to select (kHz) SELFREQ Frequency to select (MHz) FREQID Freq. ID to select. .LE.0 =>1 UVRANG UV range in klambda 0,0 => all baselines TIMERANG Time range to be selected. 1-4 = start day,hr,min,sec 5-8 = end day,hr,min,sec 0 => timerange of the data STOKES Stokes type to select. 'RR' or 'LL'; ' '=>'RR' BIF 0.0 100.0 Selected IF number 0=>1 BCHAN 0.0 2048.0 Lowest channel number 0=>all ECHAN 0.0 2048.0 Highest channel number 0=>all CHANNEL -100.0 2048.0 Reference channel number 0 => (bchan + echan)/2 <0 => referencing is not used SUBARRAY 0.0 1000.0 Subarray, 0=>1 ANTENNAS Antennas to select BASELINE Baselines with ANTENNAS See explanation. 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 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. APARM Control information: 1: pre-average interval (sec) 0 => 1/256 of the whole interval of averaging - BPARM(3) -1 => variable depending upon maximum possible fringe rate 2: zero padding for FFT 0 => no padding 1 => N zeroes 2 => 2N zeroes etc. 3: no of frequency channels to pre-average. 4: step at X-axis, in mili arcsec. 0 => (X-halfwidth)/50 5: step at Y-axis, in mili arcsec. 0 => (Y-halfwidth)/50 6: halfwidth of rectangle on the sky in X-direction; mili arcsec. 0 => is calculated 7: halfwidth of rectangle on the sky in Y-direction; mili arcsec 0 => is calculated 8: Position of rectangle center in X-direction; mili arcsec 9: Position of rectangle center in Y-direction; mili arcsec 10: 0=> find the solution; >0 => plot the sets of lines skiping solution. BPARM More control information: 1: Threshold (in sigmas) in detection maxima in fringe rate spectrum. 0 => 4 2: Time interval between beginnings of interval of averaging, minutes 0 => interval in TIMERANG 3: interval of averaging, minutes 0 => interval in TIMERANG 4: expected accuracy, mili arcsec 0 => is calculated 5: number of lines plotted 0 => all -1 => nothing to plot 6: minimum number of lines for considering crosing (multiply by NSET). 0 => 0.4(*NSET) 7: number of iterations in elimination of extra lines 0 => 4 8: Number of lines; criteria of stop itteration (LINES) 0 => 0.6(*NSET) 9: Level of printing; 0 => minimum 1 => middle 2 => max. See explain. LTYPE -10.0 10.0 Type of labeling: 1 border, 2 no ticks, 3 - 6 standard, 7 - 10 only tick labels <0 -> no date/time OUTTEXT Filename in which the list of found components is written. BADDISK 0.0 9999.0 Disks to avoid for scratch DOTV -1.0 1.0 > 0 Do plot on the TV, else make a plot file GRCHAN Graphics channel; 0 => 1 ---------------------------------------------------------------- FRMAP Type: Task Use: To create a fringe rate map of the source. The data to be used can be selected using a variety of criteria e.g. Uvrange, Timerange or by selecting data from baselines determined by the ANTENNAS and BASELINE adverbs. Calibration and flagging can be applied to the data before the fringe rate mapping. The data can be averaged over a range of frequency channels within a given IF as well as over a time interval. The FFT can be optionally padded with zeroes and is computed with Hanning weighting. The fringe rate spectra can be calculated after referencing the data to a reference frequency channel's data. The reference channel should be selected on the basis of a simple structure, pointlike or gaussian. It is a good idea to use tasks FRPLT or VPLOT before FRMAP to examine the visibilities of all channels to provide a relevant selection of the reference channel. Having calculated the fringe rates for each SETTIMES (baseline-time) as well as the coefficients of sensitivity of the fringe rate to position of a feature in RA(X) and declination(Y), we obtain the equations of straight lines UDOT*X(I) + VDOT*Y(I) = FR(I) describing the position of component I on the sky. If there is only one component for each frequency channel its position is determined by intersection of the straight lines set and it can be determined by a least square method. Having several components for each frequency channel we obtain an ambiguity in the crossing lines. The components position can be determined in this case by finding the places of highest density of crossing lines. (Details can be read in Giuffrida,T.S, 1977 PH.D. thesis MIT; and in Walker R.C. Astr. J. v86, 9,1323, 1981). The program plots the straight lines on the TV or prepares a plot file. Then the program determines the positions of higher density of crossing lines. The coordinates in RA and DEC of the found components are written in an output file. Adverbs: USERID.....Input file user number. Ignored. 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 list. If the data is a multi-source file FRMAP will form the map for the first source specified. If blank, the first source in the data will be mapped. Apparent RA and DEC are taken from SU table. If the data is a single source file no source name need be specified. Apparent RA and DEC are colculated. The calculation's accuracy is better 10^(-6). 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 overide that of FREQID, however setting SELBAND and SELFREQ may occasionally result in an ambiguity, in which case the task will request that you use FREQID. UVRANGE....Range (min, max) of projected baselines to include 0,0 => all baselines (units: klamda) TIMERANG...Time range of the data to be selected. In order: Start day, hour, min. sec, end day, hour, min. sec. Days relative to ref. date. 0 => time range of the data STOKES.....The desired Stokes type of the output data: ' ' => RR 'I','V','Q','U','IQU','IQUV','IV','RR','LL','RL', 'LR','HALF' (=RR,LL), 'FULL' (=RR,LL,RL,LR) BIF........Selected IF to map. 0=>1. Only one IF can be selected. So EIF is fixed to equal BIF. BCHAN......First channel to select. 0=>all. ECHAN......Highest channel to select. The channels averaging within this channel range is set by APARM(3). CHANNEL....CHANNEL sets the reference channel number. If CHANNEL = 0 then reference channel number is equal (bchan + echan)/2 If CHANNEL < 0 referencing is not used. This option can be used in the case of continuum sources for estimating the error of the source coordinates and when there is a problem to find a channel with simple structure. The time of averaging can be limited in this case by frequency unstability of local oscilators. SUBARRAY...Subarray number to select. 0=>all. ANTENNAS...A list of the antennas forming the baselines. If any number is negative then all antennas listed are NOT to be used and all others are. BASELINE...Baselines between antennas named in ANTENNAS and those named in BASELINE are selected.. There are four possible combinations of ANTENNAS and BASELINE: 1. ANTENNAS = 0; BASELINE = 0. All possible baselines are selected. 2. ANTENNAS <>0; BASELINE = 0. a)All ANTENNAS > 0 Baselines between antennas named in the ANTENNAS list are selected; b)Some ANTENNAS < 0 Baselines between antennas named in the ANTENNAS list are DE-selected; 3. ANTENNAS = 0; BASELINE <> 0. a)All BASELINE > 0 Baselines between antennas named in the BASELINE list and any antenna are selected. b)Some BASELINE < 0 Baselines between antennas named in the BASELINE list and any antenna are DE-selected. 4. ANTENNAS <> 0; BASELINE <> 0. a)All ANTENNAS>0; All BASELINE>0 Baselines between antennas named in ANTENNAS and those named in BASELINE are selected. b)Some ANTENNAS<0 .OR. Some BASELINE<0 Baselines between antennas named in ANTENNAS and those named in BASELINE are DE-selected. 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 multisource 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 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.....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......Specifies the version of the BP table to be applied (if DOBAND > 0. 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). APARM......(1) sets the pre-average time interval to be used before the FFT. Vector averaging is performed. If APARM(1) = 0 then the pre-average time interval is equal 1/256 of the averaging interval - BPARM(3) IF APARM(1) = -1 then variable pre-average times are calculated for a given set depending upon maximum possible fringe rate. This dynamical change of a pre- average time minimises the computing time but has problem of correct determination of sigma because the spectral components occupy the whole spectral window and it complicates determination of the noise. So using dynamical pre-averaging it is useful to decrease the threshold of spectral line discrimination (BPARM(1)). It is recomended to avoid using the dynamical pre-averaging if possible. Number of data points (with unzero weights) in the averaging interval for a given baseline-time has to be more than half of N = BPARM(3)/(pre-avg time). If number of actual data points at the average interval (BPARM(3)) is less than 512 the pre-avg time can be choosen actual pre-avg. time. (2) defines the zero padding to be used in the FFT. 0=> no padding; 1=> N zeroes added; 2=> 2N zeroes added etc. (3) sets the number of channels to be pre-averaged for each FFT. The channel range over which this averaging takes place is defined by BCHAN and ECHAN. (4) step in X-axis (RA), in milli arcsec. 0 => (X-halfwidth)/50 (5) step in Y-axis (DEC), in milli arcsec. 0 => (Y-halfwidth)/50 (6) Halfwidth of rectangle on the sky in X-direction; milli arcsec. 0 => is calculated The mapping window is limited by rate of change of fringe rate during the averaging time and as a result the signal is smeared. The smearing is greater for the more distant components. The sizes of the window depend upon the time averaging and the geometry of the interferometers. (7) Halfwidth of rectangle on the sky in Y-direction; mili arcsec. 0 => is calculated. (8) Position offset of rectangle center in X-direction; in mili arcsec. (9) Position offset of rectangle center in Y-direction; in mili arcsec (10) If zero the program provides both the plotting of the lines' set and the solution for the components by finding the places of highest density of the lines and applying a least square method. If >0 the program provides the plotting of the lines' set only providing opportunity to the user to resolve components himself. This last option saves computing time. BPARM......(1) Threshold (in sigmas) in detection maxima in fringe rate spectrum. 0 => 4. See explanation of APARM(1). (2) Time interval between beginning of each averaging interval, minutes 0 => interval in TIMERANG. (3) Averaging interval, minutes 0 => interval in TIMERANG. (4) The map's accuracy used in criteria of terminating of deleting lines in the mapping. mili arcsec. 0 => calculated (5) number of lines plotted. 0 => all lines are ploted; -1 => nothing is plotted (6) minimum number of lines for considering crosing (multiply by NSET) a given rectangle. 0 => 0.4(*NSET) (7) number of iterations in elimination of extra lines; 0 => 4 (8) Number of lines in criteria of itterations stop; If the number of the lines crossing a given rectangular cell is bigger than this parameter the line giving the biggest deviation from the solution is eliminated. This process is terminated when the number of crossing lines is equal to this parameter (*NSET). 0 => 0.6(*NSET) (9) Level of printing. 0 => minimum. The numbers of a current time interval, baseline and channel are printed; 1 => medium. In addition to mimimum level the information about rectangular cells with maximum crossing lines is given. So numbers of a set (combination of baseline and time), components, and corresponding fluxes are printed together with coordinates of the rectangular cell and solution for position of the feature are printed. 2 => maximum. In addition to medium level equations of lines for each set are printed. LTYPE......Labelling type: 1 = border, 2 = no ticks, 3 - 10 = standard, with 7-10 all labels other than tick numbers and axis type are omitted. Less than 0 is the same except that the plot file version number and create time are omitted. OUTTEXT....The name of a disk file into which the list of founded components is written. BADDISK....A list of disks on which scratch files are not to be placed. This will not affect the output file. DOTV.......> 0 => plot lines directly on the TV device, otherwise make a plot file for later display on one or more devices (including the TV if desired). GRCHAN.....Graphics channel (1- 7) to use for line drawing. 0 => 1 ---------------------------------------------------------------- FRMAP: Task to produce the map of the source using the fringe rates. Documentator: L.R. Kogan Related programs: FRPLT Fringe rates are determined precisely using three steps. The first one uses criteria of maximum amplitude in the fringe rate spectrum and discrimination of the features with amplitu- des less than a selected threshold. The value of this threshold is equal CO*SIGMA. Sigma is calculated as an average value of the spectrum. CO is a coefficient which is selected by BPARM(1). A large value of this coefficient can lead to missing some features; Small value can produce some false features. The compromise for the coefficient is between 2 and 5. The second step in fringe rate determination is based on fitting amplitudes, fringe rates and phases of features with measured visibilities as a function of time. Zero points are excluded from the fitting. This exclusion suppress the false maxima occured due to lack of data in some time points. The new amplitudes of features are compared again with the threshold and false maxima are discriminated against. The final solution for fringe rates (the third step) is found by non linear least square method. Having found fringe rates for all given baselines and all given times - SETTIMES, the program maps each frequency channel or group of pre-averaged channels separately. The selected rectangular window in the picture plane (APARM(6) - APARM(9)) is devided by number of small rectangular cells. The size of these cells is determined by expected angular resolution and can be selected by user (APARM(4), APARM(5)) or calculated. The program finds the cells which are intersected by the number of lines larger than the threshold setting by user. This limiting number of lines = BPARM(6)* SETTIMES, where SETTIMES is number of sets (baselines-times) and is recomended to be about (0.5 - 1.0)*SETTIMES. If there are several close cells intersected by the number of lines larger than the threshold then the program finds the cell with maximum number of crossing lines (in this cluster of cells) and eliminates the remainder. Having found the cells with maximum lines' density the program applys least square method to determine the components' position. The least square is repeated several times with elimination of a line giving maximum deviation from the solution on each iteration. The iteration process is terminated if the number of crossing lines is less the selected limit BPARM(8), the number of iterations is bigger than a given limit BPARM(7), or the given accuracy BPARM(4) is achieved. The final list of components found is printed in the ouput file for each frequency channel or for each group of preaverage channels.