; BLING ;--------------------------------------------------------------- ;! find residual rate and delay on individual baselines ;# TASK CALIBRATION VLBI AP OOP ;----------------------------------------------------------------------- ;; Copyright (C) 1995-1997, 1999-2004, 2006, 2009-2010 ;; 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 ;----------------------------------------------------------------------- BLING LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC BLING: Task to determine residual delays and rates 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 unit # CALSOUR Calibrator sources QUAL -10.0 Calibrator qualifier -1 => all CALCODE Calibrator code ' '=>all STOKES Polarizations to process TIMERANG Time range to use. ANTENNAS Antennas to use. 0=all BASELINE Baselines with ANTENNAS. SUBARRAY 0.0 1000.0 Subarray. 0 => 1 SELBAND Bandwidth to select (kHz) SELFREQ Frequency to select (MHz) FREQID Freq. ID to select. BIF 0.0 First IF to use 0 => 1 EIF 0.0 Last IF to use 0 => max BCHAN 0.0 2048.0 Lowest channel number 0 => 1 ECHAN 0.0 2048.0 Highest channel number 0 => max UVRANGE Range of uv distances to use 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. PDVER PD table to apply (DOPOL>0) 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. 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' OPCODE Type of solution: ' ' => 'INDE' SOLINT Solution interval (min) INFILE Control file APARM Task enrichment parameters: 1: minimum integration time in sec (0 => 1.0) 2: > 0 => subtract model 3: > 0 => stack data 4: min SNR (0 => 5.0) 5: minimum coherence (%) 0 => 20% 6: delay precision tuning (see help for BLING) 7: rate precision tuning (see help for BLING) DPARM Delay-rate windows: 1: multiband delay centre 2: multiband delay width 3: single-band delay ctr 4: single-band delay wdth (delays in nanosec) 5: rate centre (mHz) 6: rate width (mHz) 7: accel. centre (uHz/sec) 8: accel. width (uHz/sec) 9: accel. step (uHz/sec) DOUVCOMP If > 0 then use compressed scratch files. BADDISK List of disks not to be used for scratch files. ---------------------------------------------------------------- BLING Task: BLING determines the residual group delay and phase rate and acceleration for each baseline in an array. The results are stored in a baseline fringe solution (BS) table attached to the uv data file. The task BLAPP will read a BS table and distribute the baseline-based quantities between telescopes. Model images made with both values of IMAGR's DO3DIMAG option are handled correctly, as are multi-scale images. Set NMAPS = NFIELD * NGAUSS. Adverbs: Input data file: 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. Source selection (multisource files only): CALSOUR....List of sources for which residual fringe parameters are to be determined, i.e. the calibrator sources. If all entries are blank then all sources in the input file will be used. If any entry is preceded by a minus sign then all sources in the input file other than those listed in CALSOUR will be used. QUAL.......Only sources with a source qualifier number in the SU table matching QUAL will be used if QUAL is not -1. This selection criterion is applied to sources selected using CALSOUR. 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. This selection criterion is applied to the sources selected using CALSOUR and QUAL. Note that the source selection parameters should only specify a single source if a model is to be subtracted before searching for fringes. Data selection: STOKES.....The polarizations to use. This should be a concatenation of any of the four polarization correlations RR, LL, RL and LR or one of the special values 'HALF' (RR and LL) or 'CROS' (RL and LR). Default: 'HALF' TIMERANG...Time range of the data to be used. In order: Start day, hour, min. sec., end day, hour, min, sec. Days relative to the reference date of the observations. Default: from the beginning of the observations in the input file to the end. ANTENNAS...A list of antennas used, in combination with BASELINE, to select the baselines to process. If all entries are positive include only baselines including the listed telescopes; if any entry is negative use all telescopes not listed. Default: use all baselines. BASELINE...Antennas appearing at the other end of selected baselines from telescopes selected using ANTENNAS. Example: to select baselines 1-6,1-8, 2-6 and 2-8 set ANTENNAS=1,2; BASELINE=6,8. Default: use all baselines involving telescopes selected using ANTENNAS. SUBARRAY...Subarray number to use. Default: 1. SELBAND....Bandwidth of the data to be selected. If more than one IF is present SELBAND is the bandwidth of the first IF required. Units = kHz. Default: use FREQID. 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. Default: use FREQID. FREQID.....Frequency (FQ) group identifier to select (you may determine which is applicable from the OPTYPE='SCAN' listing produced by LISTR). If either of SELBAND or SELFREQ are set then their values overide that of FREQID unless SELBAND and SELFREQ are ambiguous; if SELBAND and SELFREQ are ambiguous then the task will request that you use FREQID. BIF........First IF to use. Default: 1 EIF........Last IF to use. Default: highest IF number in file. BCHAN......First channel to use. Default: 1 ECHAN......Highest channel to use. Default: highest channel number in file. UVRANGE....Range of projected spacings to be used in 1000's of wavelengths. Default: 1.0 to 1.0E10 Calibration switches (multisource files only): 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 the data. Default: highest version number DOPOL......If > 0.5 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 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......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). Source model to be divided into the data. IN2NAME....Cleaned map name (name). Standard defaults. For a single source file the model determined by SMODEL is used instead of the CLEAN components if IN2NAME = ' ' and IN2CLASS = ' '; For a multi-source file a point source with flux given in the SU table is used instead of a CLEAN components if IN2NAME = ' ' and IN2CLASS = ' '. Note: a CLEAN image for only a single source may be given although it may be in a multisource file. 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. NOTE: when using a model derived from data with difference uv sampling it is best to use 'DFT' 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. If CMODEL is ' ' clean components will be used if present and the image if not. Note: A normal CLEAN restored image is not a suitable model as it has been tapered by the restoring beam. A CLEANed image restored with a very small restoring beam is usable. Note that IMAG models are USUALLY scaled by the beam area and CC models are scaled to match the source-table total flux when appropriate. BLING DOES NOT DO THESE SCALINGS. Task control: OPCODE ....Solution type 'INDE' => independent delay and rate solutions for each IF and polarization. Use for multi-IF data without phase cal. 'VLBA' => single delay and rate for all IFs in each polarization. Use for VLBA data or any other multi-IF data with more than one phase cal per IF. 'MK3 ' => multiband and single-band delays and rates for all IFs in each polarization. Use for Mk3 VLBI data or any other multi-IF data with only one phase cal per IF. 'RATE' => fit rate and accelerations only. Use on one channel only when interpolating rates from fringe finders to program sources. SOLINT.....Solution interval in minutes. A solution interval may be cut short to avoid crossing a scan boundary if an index table is present. The solution inter- val may be overridden for particular times and baselines in the control file. 0 -> 5 min INFILE.....The name of a text file containing solution inter- vals and search windows for specific baselines and time ranges. APARM......Miscellaneous control parameters. APARM(1)...Minimum integration time in file in seconds. This is used to calculate the amount of data storage that BLING must allocate. It is usually better to set this too small than too large although smaller values make it more likely that you will run out of memory. <= 0.0 -> 1.0 sec APARM(2)...Model division flag. If this has a positive value then a model will be divided into the data before searching for fringes. APARM(3)...Baseline stacking flag. If this has a positive value baseline data will be stacked. Baseline stacking uses the data from baselines i-k and k-j (for all k.ne.i and k.ne.j) to increase the sensitivity on baseline i-j. Do not enable stacking if your file contains multiple integration times. APARM(4)...Minimum SNR for detection. <= 0 -> 5.0 APARM(5)...Minimum coherence value in percent. The lowest ratio of the vector amplitude sum and the scalar amplitude sum that will be accepted. <= 0 -> 20% APARM(6)...Delay precision control. APARM(7)...Rate precision control. These parameters control the amount of padding used in the FFT searches. >= 0 pads by a factor of 2 -1 ................... 4 -2 ................... 8 -3 ................... 16 -4 ................... 32 -5 ................... 64 -6 ................... 128 <= -7 .................... 2 Increasing the padding may give a little extra precision but will slow BLING down by a factor of up to (approximately) 2 ^ -(APARM(5) + APARM(6)). It is rarely worth while to use extra padding. DPARM......Default search windows (may be overridden in the control file). Window widths less than or equal to zero default to the full ambiguity range. DPARM(1)...Multiband delay window centre (ns) DPARM(2)...Multiband delay window width (ns) DPARM(3)...Single-band delay window centre (ns) DPARM(4)...Single-band delay window width (ns) DPARM(5)...Fringe rate window centre (mHz) DPARM(6)...Fringe rate window width (mHz) DPARM(7)...Acceleration window centre (uHz/s) DPARM(8)...Acceleration window width (uHz/s) DPARM(9)...Acceleration search step (uHz/s) DPARM(9) <= 0.0 turns off the acceleration search unless overridden in the control file. DOUVCOMP...UV data compression flag. If this is greater than zero then BLING scratch files will be written in compressed form. This reduces the amount of disk required to run BLING but can decrease the precision of intermediate results and can affect weighting and flagging. Avoid compressing scratch data if your original data is uncompressed or if you are dividing by a model unless disk space is at a premium. BADDISK....A list of disks not to be used for scratch files. ------------------------------------------------------------------------ BLING: Task to find fringes on individual baselines. DOCUMENTOR: Chris Flatters, NRAO RELATED PROGRAMS: BLAPP, PRTBS, FRING INTRODUCTION BLING searches for fringes in residual delay and rate on individual baselines and stores the results in a baseline solution (BS) table attached to the uv data. These results can be applied to the data by using BLAPP to resolve the baseline-based quantities into antenna-based terms. This procedure is similar to that described by Alef and Porcas (Astron. Astrophys. vol. 168 p365, 1986). While BLING is usually much slower than FRING, it offers a greater level of control. Search windows and solution intervals can be specified for individual baselines and time ranges and BLING can search for a fringe acceleration term (the time derivative of the residual rate). You should normally use FRING to determine rates and delays and restrict your use of BLING to cases where FRING may have problems. Cases where BLING may be preferable to FRING include the following. * Fringe acceleration searches are needed. This is only likely for space VLBI. * Fringe locations can be predicted, allowing tight, off-centre windows to be used. * Differing baseline sensitivities make it desirable to use different solution intervals for different baselines. * Differing baseline sensitivities defeat FRING's strategy for choosing baselines for the coarse search (for any given antenna, FRING will look at the baseline from that antenna to the reference antenna and will try a baseline to a secondary reference if fringes are not found but will not try all possible secondary references while BLING will examine all of the baselines to a given telescope. SOLUTION MODES BLING has a number of modes which allow it to search for different sets of fringe parameters. The mode is chosen by setting OPCODE and the parameters to be solved for in each mode are shown in the following table. +------+-----------------+-------------------+------+ | Mode | Multiband delay | Single-band delay | Rate | +------+-----------------+-------------------+------+ | INDE | no | yes | yes | | VLBA | yes | yes | yes | | MK3 | yes | yes | yes | | RATE | no | no | yes | +------+-----------------+-------------------+------+ 'INDE' mode produces independent delay and rate solutions for each IF while the other 3 modes produce a combined solution that applies to all IFs. 'VLBA' mode differs from 'MK3 ' mode in that multiband delay is assumed to be equal to single-band delay in 'VLBA' mode but not in 'MK3 ' mode. Acceleration searches may be requested independently of the mode setting. BASELINE STACKING BLING is capable of "stacking" data from different baselines. This technique is explained in the Schwab and Cotton paper on global fringe-fitting (Astron. J. vol. 88 p688, 1983) and is also used in FRING. The basic idea is that the slope of the summed visibility phase from baselines i-j and j-k with respect to frequency is wholly determined by the residual delays of i and k (since the delay at j cancels in the addition) and can therefore be used to supplement the data from baseline i-k. In the limiting case where there are N identical telescopes and one which is much less sensitive this technique will reduce the fringe-detection threshold by a factor of sqrt(N). BLING can stack data that uses one intermediate antenna while FRING can use up to two intermediate antennae. Allowing a second intermediate antenna gives only a modest improvement over using a single intermediate. In reality neither BLING nor FRING average phases directly, as suggested above, but sum a vector quantity with the phase of the visibility data and an amplitude equal to the visibility weight. This procedure is more appropriate to a process that uses a Fourier transform (as both tasks do in their coarse searches) but may break down if the source is not dominated by a bright unresolved component. You may therefore need to disable baseline stacking if you are observing a source with complex structure and do not have a model that can be divided into the data. Stacking is enabled by default but will be disabled if you set APARM(2) to a positive number. BLING will use all of the possible intermediate antennae in the data set, regardless of whether they are listed in the ANTENNAS and BASELINE adverbs (which determine which baselines BLING will search for fringes). If you wish to exclude an antenna from the set of intermediates then you should use UVFLG to flag data from that antenna and unflag the data after running BLING. ACCELERATION SEARCHES The acceleration search is carried out in a different way to the searches in delay and rate. If an acceleration search is carried out then BLING will try a number of coarse searches at different acceleration values and pick the acceleration value that gives the best degree of coherence as the starting point for the fine search. This means that you must specify an acceleration step size to use in the coarse search as well as a search window. If the step size is zero or negative then there will be no search in acceleration. It should be obvious from the above that enabling acceleration searches will slow the program down considerably. Since enabling acceleration searches adds additional parameters to be modelled, it will also tend to degrade the quality of your solutions if you turn it on when it is not needed. You should, therefore, restrict your use of acceleration searches to those cases where it is absolutely necessary. CONTROLLING BLING The search windows and solution interval may be changed for particular time ranges and baselines using a control file specified as INFILE. The control file should contain a number of baseline groups Each group should start with a header card with the general form telescope1 telescope2 / This informs BLING that the following records apply to baseline telescope1-telescope2 where telescope1 and telescope2 are either telescope names taken from the antenna table of the special name "ANY". Thus PT MK / starts a group applying to the Pie Town - Mauna Kea baseline while PT ANY / or ANY PT / starts a group applying to any baselines involving Pie Town and ANY ANY / starts a group applying to any baselines. The header card should be followed by one or more cards having 14 fields. The fields are as follows. 1 integer Annual day number (Jan 1 = 1) of the day at which the parameters on this line become valid. 2 time The time (hh:mm:ss - seconds are optional) at which the parameters become valid. 3 integer Annual day number of the day on which the parameters become invalid. 4 time The time at which the parameters become invalid. 5 real The solution interval for this time range. 6 real The multiband search window centre (nanoseconds). 7 real The multiband search window width (nanoseconds). 8 real The single-band search window centre (nanoseconds). 9 real The single-band search window width (nonoseconds). 10 real The rate window centre (mHz). 11 real The rate window width (mHz). 12 real The acceleration window centre (uHz/sec). 13 real The acceleration window width (uHz/sec). 14 real The acceleration search step (uHz/sec). The group should end with a single slash ("/"). Here is an example baseline group. PT MK / 27 12:00 27 13:00 10.0 0.0 100.0 0.0 100.0 0.0 20.0 0.0 0.0 0.0 27 13:00 27 14:00 5.0 0.0 100.0 0.0 150.0 0.0 30.0 0.0 0.0 0.0 / The following rules apply. * All of the windows must be defined in each card regardless of whether the corresponding parameter will be solved for. Of course, the values in the fields corresponding to unused windows do not matter. * More specific baseline groups override less specific ones so that PT MK is preferred over PT ANY which is preferred over ANY ANY for any given time. * If there is no entry applicable to a given time for a particular baseline then the solution interval will be set from the SOLINT adverb and the windows will be set from the DPARM adverb. * If a delay or rate window is set to zero or a negative number then BLING will search the full ambiguity range around the given window centre. * If the acceleration search step is zero or negative then there will be no search in acceleration. CHANGES FROM 15OCT96 * BLING now uses a simple interpolation scheme to refine the fringe positions. This has allowed the default amount of FFT padding to be reduced so that BLING is now much faster. Consequently, errors listed in the BS table are now worst-case errors and realistic errors will normally be a factor of 10 to 100 better for high SNR data. CHANGES FROM 15JAN96 BLING has been extensively rewritten since the 15JAN96 release of AIPS. * You may now divide a model into the data. * Baseline stacking is now possible. * The logic for dividing the data into scans has changed. The index file is no longer used to define solution intervals and is no longer required. If an index file is present solution intervals will be truncated to avoid crossing scan boundaries defined by the index file but the scan will not be split into equal subdivisions as before. [This change was made to support the possibility of model division but also removes the need to reindex the data for efficient file access.] * Windows are now specified by a centre and width rather than a beginning and an end. The format of the control file has changed to reflect this. [This change makes BLING more amenable to predictive window-setting.] * The solution interval may now be changed for specific baselines and times. * Changes to the FFT set-up have improved the efficiency of AP memory usage allowing more FFT interpolation to be used. This has made it possible to remove the chi-squared fit used to refine the fringe positions in previous versions of BLING making the results more robust. The savings in computer time have been swallowed by the increased sizes of the FFTs, however.