AIPS NRAO AIPS HELP file for DFTIM in 31DEC18



As of Thu Apr 26 16:58:54 2018


DFTIM: Images the DFT of an arbitrary point using UV data

INPUTS

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 #
OUTNAME                            Output UV file name (name)
OUTCLASS                           Output UV file name (class)
OUTSEQ            0.0     9999.0   Output UV file name (seq. #)
OUTDISK           0.0        9.0   Output UV file disk unit #
UVRANGE           0.0              Range of projected spacings
                                     (thousands of wavelengths)
TIMERANG                           Time range to select:
                                     Start Day, Hour, Min, Sec
                                     End Day, Hour, Min, Sec
SHIFT                              Shift in asec at ref position
STOKES                             I, Q, U, V, RR, LL, XX, YY
BPARM                              Control parameters
                                   2 : averaging interval (sec)
                                   3 > 0 -> write error image
SOURCES                            Source name
QUAL            -10.0              Calibrator qualifier -1=>all
CALCODE                            Calibrator code '    '=>all
SELBAND                            Bandwidth to select (kHz)
SELFREQ                            Frequency to select (MHz)
FREQID            0.0              Frequency ID number: 0 -> 1
SUBARRAY          0.0     1000.0   Sub-array, 0=>all
BIF               0.0              First IF to include
EIF               0.0              Last IF to include
BCHAN             0.0              First channel to include
ECHAN             0.0              Last channel to include
NCHAV             0.0              Number channels to average
DOCALIB          -1.0      101.0   > 0 calibrate data & weights
                                   > 99 do NOT calibrate weights
GAINUSE                            CL (or SN) table to apply
DOPOL            -1.0       10.0   If >0.5 correct polarization.
PDVER                              PD table to apply (DOPOL>0)
BLVER                              BL table to apply.
FLAGVER                            Flag table version
DOBAND           -1.0       10.0   If >0.5 apply bandpass cal.
                                   Method used depends on value
                                   of DOBAND (see HELP file).
BPVER                              Bandpass table version
SMOOTH                             Smoothing function. See
                                   HELP SMOOTH for details.

HELP SECTION

DFTIM
Type: Task
Use:  Makes an image of the DFT of the complex visibilities found in a
      UV data base for an arbitrary point in the sky as a function of
      time and frequency.  Note that the visibilies are shifted under
      control of SHIFT and then the real parts are simply summed over
      all baselines in each time interval.  Task TBAVG makes a UV data
      set of the summed visibilities while DFTPL makes a plot of a
      selected frequency range.
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.
  OUTNAME....Output name of image(name).    Standard defaults.
  OUTCLASS...Output name of image(class).   Standard defaults.
  OUTSEQ.....Output name of image(seq. #).  0 => highest unique
  OUTDISK....Disk drive # of Output image.  0 => highest with space
  UVRANGE....Range (min, max) of projected baselines to include
             0,0 => all baselines
  TIMERANG...Time range of the data to be plotted. In order:
             Start day, hour, min, sec, End day, hour, min, sec.
             Days relative to reference date.  0 => full range.
  SHIFT......Shift in arcseconds - the data are shifted, summed, and
             then plotted.  These are shifts in arc seconds at the
             reference point -
             RA = RA0 + SHIFT(1)/cos(DEC0), DEC = DEC0 + SHIFT(2)
  STOKES.....Only one Hermitian polarization is allowed: I, Q, U, V,
             RR, LL, XX, YY.  Cross-hands do not have the Hermitian
             property and so are not allowed.
  BPARM......Control parameters:
     1:  unused
     2 = averaging interval in seconds (0 => 60)
         NOTE: an interval beginning at a sample time T1 will include
         all samples < T1+BPARM(2).  If your data occur at 5 second
         intervals and you want no averaging, set BPARM(2) < 5.  If
         you want to average pairs of samples, set 5 < BPARM(2) < 10.
     3 = > 0 -> write also an error image
     4-10 unused
  SOURCES....Source to be copied.   '  '=> all; if any starts with a
             '-' then all except ANY source named.
             NOTE: this task makes sense only if you select a single
             source.
  QUAL.......Qualifier of source to be processed. -1 => all.
  CALCODE....Calibrator code of source to be processed. ' '=> all.
  SELBAND....Bandwidth of data to be selected. If more than one IF is
             present SELBAND is the width of the first IF required.
             Units = kHz. For data which contain multiple
             bandwidths/frequencies the task will insist that some form
             of selection be made by frequency or bandwidth.
  SELFREQ....Frequency of data to be selected. If more than one IF is
             present SELFREQ is the frequency of the first IF required.
             Units = MHz.
  FREQID.....Frequency identifier to select (you may determine which is
             applicable from the OPTYPE='SCAN' listing produced by
             LISTR). If either SELBAND or SELFREQ are set, their values
             override that of FREQID.  However, setting SELBAND and
             SELFREQ may result in an ambiguity.  In that case, the task
             will request that you use FREQID.
  SUBARRAY...Sub-array number to process. 0=>all (okay if not
             calibration)
  BIF........Start IF; 0 -> 1
  EIF........End IF; 0 -> max
  BCHAN......Start channel; 0 -> 1
  ECHAN......End channel; 0 -> max
  NCHAV......Number of channels to average.  Note that ECHAN is
             adjusted if necessary to make (ECHAN-BCHAN+1) and integer
             multiple of NCHAV.  0 -> 1.
  DOCALIB....If true (>0), calibrate the data using information in the
             specified Cal (CL) table for multi-source or SN table for
             single-source data.  Also calibrate the weights unless
             DOCALIB > 99 (use this for old non-physical weights).
  GAINUSE....version number of the CL table to apply to multi-source
             files or the SN table for single source files.
             0 => highest.
  DOPOL......If > 0 then correct data for instrumental polarization as
             represented in the AN or PD table.  This correction is
             only useful if PCAL has been run or feed polarization
             parameters have been otherwise obtained.  See HELP DOPOL
             for available correction modes: 1 is normal, 2 and 3 are
             for VLBI.  1-3 use a PD table if available; 6, 7, 8 are
             the same but use the AN (continuum solution) even if a PD
             table is present.
  PDVER......PD table to apply if PCAL was run with SPECTRAL true and
             0 < DOPOL < 6.  <= 0 => highest.
  BLVER......Version number of the baseline based calibration (BL) table
             to apply. <0 => apply no BL table, 0 => highest.
  FLAGVER....specifies the version of the flagging table to be applied.
              0 => highest numbered table.
             <0 => no flagging to be applied.
  DOBAND.....If true (>0) then correct the data for the shape of the
             antenna bandpasses using the BP table specified by BPVER.
             The correction has five modes:
             (a) if DOBAND=1 all entries for an antenna in the table
             are averaged together before correcting the data.
             (b) if DOBAND=2 the entry nearest in time (including
             solution weights) is used to correct the data.
             (c) if DOBAND=3 the table entries are interpolated in
             time (using solution weights) and the data are then
             corrected.
             (d) if DOBAND=4 the entry nearest in time (ignoring
             solution weights) is used to correct the data.
             (e) if DOBAND=5 the table entries are interpolated in
             time (ignoring solution weights) and the data are then
             corrected.
             IMAGR uses DOBAND as the nearest integer; 0.1 is therefore
             "false".
  BPVER......Specifies the version of the BP table to be applied
                0 => highest numbered table.
               <0 => no bandpass correction to be applied.
  SMOOTH.....Specifies the type of spectral smoothing to be applied to
             a uv database . The default is not to apply any smoothing.
             The elements of SMOOTH are as follows:
             SMOOTH(1) = type of smoothing to apply: 0 => no smoothing
               To smooth before applying bandpass calibration
                 1 => Hanning, 2 => Gaussian, 3 => Boxcar, 4 => Sinc
               To smooth after applying bandpass calibration
                 5 => Hanning, 6 => Gaussian, 7 => Boxcar, 8 => Sinc
             SMOOTH(2) = the "diameter" of the function, i.e. width
               between first nulls of Hanning triangle and sinc
               function, FWHM of Gaussian, width of Boxcar. Defaults
               (if < 0.1) are 4, 2, 2 and 3 channels for SMOOTH(1) =
               1 - 4 and 5 - 8, resp.
             SMOOTH(3) = the diameter over which the convolving
               function has value - in channels.  Defaults: 1,3,1,4
               times SMOOTH(2) used when input SMOOTH(3) < net
               SMOOTH(2).
  DOCIRCLE...False (<= 0) means that tick marks are short lines
             extending inward from the plot borders.  True (>0)
             requests that a full coordinate grid be drawn.
  PRTLEV.....> 0 -> print time, flux, and dispersion to message file.
  LTYPE.......Labelling type, see HELP LTYPE for details:
              1 = border, 2 = no ticks, 3 or 7 = standard, 4 or 8 =
              relative to ref. pixel, 5 or 9 = relative to subimage
              (BLC, TRC) center, 6 or 10 = pixels.  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.
              Add n * 100 to alter the metric scaling.
  DOTV.......> 0 => plot 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.

EXPLAIN SECTION

DFTPL:  Plots DFT using data from a u,v data base.
PROGRAMMER: T.Bastian, Univ. of Colorado
RELATED PROGRAMS: TKPL,PRTPL,TVPL

                            COMMENTS

     DFTPL was written primarily to assist stellar observers
interested in time variable phenomena (e.g., outbursts on RS CVn's,
dMe flare stars, etc.). Since these stars are in general unresolved,
it's often pointless to make a synthesis map for each time interval.
Instead one can do the following: 1) make a large field map using the
entire XY sorted data base and identify all background sources; 2) run
APCLN or MX with boxes around these sources (but not the stellar
source of interest) and CLEAN them down to the noise; 3) using the
resulting CLEAN components as a model of the background sources, use
UVSUB to subtract the model from the UV data base; 4) use UVSRT to
sort the data into TB order.
      If NO confusing sources of any importance can be found in the
field, then of course steps 1-4 can be skipped and one simply begins
with a TB sorted (calibated and edited) data base. he UV data base on
an EXPORT tape is sorted in TB order, but one might have to use the
verb PUTHEAD to indicate this fact in the header.  This is done by
first setting KEYWORD to 'SORT' and KEYSTRING to 'TB' and typing PUTH.
      The task DFTPL allows one to plot the direct fourier transform
of the measured visibilities as a function of time for an arbitrary
shift in RA and DEC.  It will plot either points, points with error
bars, or histogram format. The averaging interval is adjustable
(BPARM(2)).  The data time segment may be specified (through APARM).
The task runs somewhat faster than UVPLT.  Hence one can moniter all
Stoke's parameters of a star with time VERY quickly, without having to
resort to generating a tedious sucession of maps.

AIPS