INNAME INPUT UV name (required) INCLASS class INSEQ sequence # INDISK disk # CALSOUR Select by source name ''=>all QUAL qualifier -1=>all CALCODE calcode ''=>all SELBAND Bandwidth to select (kHz) SELFREQ Frequency to select (MHz) FREQID Freq. ID to select < 1=>all TIMERANG Time range to use 0=>all BCHAN Lowest channel number 0=>all ECHAN Highest channel number 0=>all ANTENNAS Antennas to select 0=>all DOFIT Antennas to solve for 0=>all SUBARRAY Subarray 0=>all UVRANGE Range of uv distance for full weight 0=>all WTUV Weight outside UVRANGE 0=>0.0 WEIGHTIT 0.0 3.0 Modify data weights function DOCALIB -1.0 101.0 > 0 calibrate data & weights > 99 do NOT calibrate weights GAINUSE CL table # DOPOL -1.0 10.0 If >0 correct polarization. PDVER PD table to apply (DOPOL>0) BLVER BL table to apply. FLAGVER FG table # DOBAND >0 apply BP table See HELP DOBAND BPVER BP table # SMOOTH Spectral smoothing function See HELP SMOOTH IN2NAME CLEAN map name (optional) IN2CLASS class IN2SEQ sequence # IN2DISK disk # INVERS CC table # NCOMP # CC's/field to use FLUX CC flux cutoff NMAPS # 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 REFANT Reference antenna SEARCH Fringe search list. SOLINT Soln. interval (min) 0=>10 SOLSUB Solution subinterval SOLMIN Min solution interval SOLTYPE 'NOLS' => do FFT only 'NOFT' => do LS only other => do FFT + LS SOLMODE NRD = indep. rates/delays NR = indep. rates, no delays ND = indep. delays, no rates R = one rate, no delays RD = one rate/mb-delay RDS = one rate,mb-/sb-delays RI = one rate/iono-delay TD = mb-delay + dispersion default = NRD, see HELP DOIFS 0.0 64.0 1 => 1 solution for all IFs 2 => 2 solutions, 1 each for IFs by halves N => N solutions, 1 each for NIF/N IFs 0 -> 1 (use 1 for T, S) SOLMODE must include N to do each IF individually (DOIFS is ignored) OPCODE 'ZRAT' => zero rates for more, See HELP KRING CPARM 1 min T_int(sec) 0 => 2 2 delay win(ns) 0 => Nyquist 3 rate win(mH) 0 => Nyquist 4 SNR cutoff 0 => 3 -1 => pass all 5 FFT baseline stacking? 0 => yes 1 => no 6 search to which antennas? 0 => all 1 => only those on SEARCH list 7 >0 average RR and LL 8 <=0 rereference solutions 9 max SOLINT (min) 0=>10 10 >0 try extrapolation and reverse traverse [possibly broken, see HELP] SNVER Output SN table, 0=>new table ANTWT Ant. weights (0=>1.0) BIF First IF included when when SOLMODE has no N EIF Last IF included when when SOLMODE has no N PRTLEV Print level: 0-> count solns 1-> LS info 2-> FFT info BADDISK Disk # to avoid for scratch files.

KRING Task: This task determines phase, rate, and delay corrections to be applied to a uv data set given a model of the source(s). The corrections are written to an SN table attached to the input Multi-Source UV data set. *** The delay/rate searchs are automatically turned off if less than two points are available along the corresponding freq/time axes. *** Plus signs next to the SNR during the FFT stage indicate the level of baseline stacking used to attain the reported SNR. SNRs for baselines with differing amounts of stacking should not be compared! *** The LS and FFT SNRs now agree with each other for unstacked data processed one baseline at a time [ostensibly to < 1 percent]. QUESTIONS, COMMENTS? [write to daip@nrao.edu] [Last documentation overhaul = 20 Oct 1999 [coming one day? - probability of false detection, multiple SN tables, BL tables...] 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. 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=>first available. ECHAN......Highest channel to use. 0=>highest available. 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. 0 => 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. 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). GAINUSE....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 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 three 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 is used to correct the data. (c) if DOBAND=3, the table entries are interpolated in time 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 via 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 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. Note that the desired refant is not required to be the primary search antenna. You should choose the REFANT to be an antenna that is present during most of the observation. SEARCH.....List of prioritized reference antennas to be used for fringe searching during the FFT stage. KRING constructs an internal search list to determine the order in which to perform the FFTs. This search list is constructed by first copying the elements of SEARCH. Finally, all remaining antennas antennas are appended to the search list in numerical order. You can limit the search to only the specified elements of the SEARCH list by setting CPARM(6). Only baselines where at least one antenna appears in the search list will be searched for fringes. You should explicitly order the antennas in terms of decreasing sensitivity if at all possible. SOLINT.....The solution interval. Note that this is only a recommended solution interval. The actual solution interval used by KRING will be changed in order to divide each scan evenly into an integral number of data chunks. SOLINT is in minutes; the default value (SOLINT=0) is 10 minutes. SOLINT values larger than 10 are reset to 10 minutes unless CPARM(9)>0. NB: If SOLINT > 0.75*Scan, 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. SOLTYPE....If 'NOLS', only a FFT delay/rate search is performed. If 'NOFT', only a LS delay/rate search is performed. Otherwise, a FFT search is followed by a Least Squares search. SOLMODE....This four character string controls the types of parameters to be solved for. In any order, the following may be specified: N -> solve for N sets of quantities [ per IF ] *** see DOIFS for solutions spanning > 1 IF.*** R -> solve for rate [ per IF or only one common to all IFs ] D -> solve for delay [ per IF (single band delays) or only one (multi-band delay) ] S -> solve for stair-step delay [ only one, usually only needed for MkIII data where pulse-cals have been used ] I -> solve for an ionospheric delay [ only one, approx. proportional to inverse frequency ] T -> solve for an ionospheric delay [ only one, exactly proportional to inverse frequency ] 4,2, or 1 -> use a factor of 4,2, or 1 of zero padding in the FFTs.[use 4,2, or 1 for speed over accuracy] *** If N is specified, I,S,T are ignored. [T also stores the ionosphere in the mb-delay column so you can see the solved for values using SNPLT. The actual phase/delay solutions stored using I or T are identical.] *** Phases are always solved for*** Commonly encountered modes would be: NRD = APARM(5)=0 in FRING RD = APARM(5)=1 in FRING RDS = APARM(5)=2 in FRING ND, D, DS = same as NRD, RD, and RDS respectively but do not solve for rates NR, R = same as NRD and RD, respectively but do not solve for any type of delays Default is NRD . *** Note Bene, SOLMOD = 'ND' is different from SOLMOD = 'NRD', OPCODE='ZRAT' . The latter first determines the best fitting rate along with other solutions and then zeroes the rate solution in the final SN table - this is usually what you want. DOIFS......If DOIFS is set to N, then determine N solutions using NIF/N IFs in each one. Note that NIF must be an integer multiple of N or the task will quit. The default is 1 but will be set to 0 (separate solutions for each IF if SOLMODE contains an 'N'). OPCODE.....Solution masking to be performed _after_ fringe-fitting ' ' no masking 'ZPHS' zero phases in output SN table 'ZRAT' zero rates in output SN table 'ZDEL' zero delays in output SN table If CPARM(8)>0, OPCODE is forced = ' '. CPARM(1)...The minimum integration time of the data (sec); 0 => 2 'VLBA' seconds It is important to get this number right to within 20 percent. E.g., if you've averaged up 1 second data to 10 seconds, setting this to 10 is okay so long as there are only a very few points with shorter than 10 second integration times. If you set this to 1 second, you will regret it. CPARM(2)...The delay window FW to search (nsec) centered on 0 delay. <= 0 => full Nyquist range. [Use SOLMOD to turn off the delay search.] CPARM(3)...The rate window FW to search (mHz) centered on 0 rate. <= 0 => full Nyquist range. [Use SOLMOD to turn off the rate search.] CPARM(4)...The minimum allowed signal-to-noise ratio. <0 => 3 The SNR calculation is described in AIPS Memo 101. [You might consider setting this to 5.] CPARM(5)...Number of baseline combinations to use in the initial, FFT 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. [Solutions formed using combinations of baselines are marked with a plus for singly indirect combinations and with two pluses for doubly indirect combinations.] CPARM(6)...If CPARM(6)=1, only baselines to those antennas on the SEARCH list are searched during the FFT stage. Otherwise, other baselines are eventually searched until either fringes have been found to each antenna, or no baselines remain to be searched. CPARM(7)...If >0, RR and LL data are averaged together and only a single solution is determined for both polarizations. This is useful when reducing polarization data. CPARM(8)...If <= 0 then the phase, rate and delays will be re-referenced to a common antenna. CPARM(8)=1 is only desirable for VLBI polarization data. Using this option also forces OPCODE = ' '. CPARM(9)...If SOLINT>10 is desired, you must set CPARM(9)>0 . This is necessary to prevent accidentally requesting more memory than your computer can deliver and locking up computer. CPARM(10)..Try Hard Option. If CPARM(10)>=0, When KRING is ready to do the initial FFT-based fringe search, it will first try to initialize residual fringe-fit delay and rate solns for each antenna using an average of all good solutions found in the SN table. Only those antennas for which acceptable solutions are not found will then be FFTd to find fringes. This does not preclude the final Least Squares refinement. [20 Oct 1999, it has been reported that CPARM(10) is broken - it may trash the solutions - dont try it unless you have the time to re-run KRING if need-be.] 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. This really is unnecessary in most cases now. BIF........First IF included when when SOLMODE does not contain an N (all IFs receive the solution found for the appropriate group of IFs, but only BIF-EIF are used to find it). EIF........Last IF included when when SOLMODE does not contain an N (all IFs receive the solution found for the appropriate group of IFs, but only BIF-EIF are used to find it). PRTLEV.....Print flag, 0=minimal - (almost nothing). 1 = LS solution information + scan information 2 = FFT solution information 3 = nothing really new. >3, all kinds of debugging info. BADDISK....A list of disk numbers to be avoided when creating scratch files.

KRING - who wrote it? ? who rewrote it? kdesai@nrao.edu KRING - documentation? - kdesai@nrao.edu [with input from mrupen@nrao.edu] KRING - currently maintained by? - kdesai@nrao.edu need help? - daip@nrao.edu For some basic introduction to fringe-fitting, please see the discussions in: Chapter 9 of Interferometry and Synthesis in Radio Astronomy, AR Thompson, JM Moran, & GW Swenson Jr., Krieger Publishing, 1991 Global Fringe Search Techniques for VLBI, FR Schwab, WD Cotton, AJ, 88, 5, 1983 The Calculation of SNR in KRING's FFT stage, KM Desai, AIPS MEMO 101, 1998 The AIPS cookbook also describes how and when KRING should be used. Brief description: KRING is a rewrite of the AIPS fringe-fitting task FRING. BLING/BLAPP is an alternate method of fringe-fitting in AIPS. These tasks all implement in one way or another the global fringe- fitting algorithm described in Schwab and Cotton. KRING differences from FRING: MEMORY USAGE: -KRING uses up to a third less memory for full Nyquist window searches and can save even more if smaller search windows are specified. -KRING uses an indexing scheme to track the integration times on different baselines. This scheme has its weaknesses [it does not gracefully handle the case when the integration times are not all multiples of the shortest integration time] but in most data sets now produced by the VLBA correlator, uses (N-2)*(N-1)* T_int_max / (2 * T_int_min) less memory [N is the number of stations in the data set]. SCRATCH FILE USAGE: -FRING creates a scratch file consisting of calibrated _uncompressed_ data. If a complicated source model is used, this scratch file is potentially _SIX_ times bigger than the original [compressed] data set. KRING requires an NX table and creates scratch files for one scan at a time. This results in much smaller scratch file usage at the cost of some overhead to create each scratch files. This is a noticeable penalty when fringe-fitting phase-referenced observations. Currently, the scratch file grows as longer scans are found but does not shrink when shorter scans are encountered. SOLUTION INTERVALS: KRING uses a different scan-breaking algorithm to try to make all solutions in a scan the same length - this algorithm may be more robust than FRING when: the user asks for one solution per scan, the TIMERANG is set. RESTRICTED DELAY/RATE SEARCHES KRING implements delay and rate searching more uniformly so that the options to turn off delay or rate searches now work- previously it was difficult to turn off the rate search. SOLUTION EXTRAPOLATION and REVERSE TRAVERSE KRING can try to extrapolate solutions from previously found solutions. Before doing an FFT, KRING will check if the average of all previously found solutions has an SNR larger than the cutoff. If so, the delay and rate are adopted and a new phase solution is computed. If the average solution's SNR is too low, KRING falls back to doing the FFT. This can be expensive for data of uniformly poor quality of with uniformly weak fringes and should be turned not be used in such cases. This option is off by default. [20 Oct 99, it has been reported that CPARM(10) is broken, I don't recommend its use until further notice. Sorry for the inconvenience!] SNR CALCULATIONS: The SNR calculation in KRING is based upon an analytical expression for the SNR that can be found in AIPS memo 101. Note that the SNR calculations from the LS and FT stages are only expected to agree when processing one baseline at a time [but, in that case, they are expected to agree to within 1 percent].