AIPS NRAO AIPS HELP file for BPWAY in 31DEC19



As of Tue Dec 18 4:51:12 2018


BPWAY: Determines channel-dependent relative weights

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 #
OPTYPE                             'SORC' else 'SCAN'
SOURCES                            Source name
QUAL            -10.0              Calibrator qualifier -1=>all
CALCODE                            Calibrator code '    '=>all
TIMERANG                           Time range to use
FREQID                             Freq. ID to select.
SUBARRAY          0.0     1000.0   Sub-array, 0=>all
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                             Spectral smoothing function
                                   Dangerous here - see help.
BIF                                Lower IF to include
EIF                                Upper IF to include
ICHANSEL                           Array of start and stop chan
                                   numbers, plus a channel
                                   increment and IF to be used
                                   to select channels to sum to
                                   find average spectral rms.
FPARM                              (1) > 0 rolling T buffer to
                                      find time rms F(1) times
                                   (2) Normal time interval
                                      between samples (sec)
                                      IMPORTANT TO BE ~RIGHT
                                   (3) Flag any visibility amp
                                      > F(13) before time rms
                                      0 -> 1.E6
                                   (4) Smoothing type
                                   (5) Smoothing width (min)
                                   (6) Smoothing support (min)
                                   (7) Minimum weight factor
                                   (8) Maximum weight factor
                                   (9) > 0 -> average Stokes
                                   (10) > 0 ignore weights
                                       SEE HELP
FQCENTER                           >= 0 -> center frequency axis
BADDISK                            Disks to avoid for scratch

HELP SECTION

BPWAY
Task:  This task examines data, one scan at a time.  In each scan, the
       task finds the rms versus time for each baseline over time
       intervals, which are usually fairly short, one polarization and
       one spectral channel at a time.  This operation is done with a
       moving window to determine the rms at the center of the window.
       The spectra of rmses are normalized and then written to a table
       where they are sorted, smoothed over time, and then re-sorted
       to time order.  These time smoothed rmses are then used to set
       the weights of the data written to a new data set.  This data
       set is written in uncompressed form to avoid loosing all the
       weights just computed.

       Note that any calibration, particularly bandpass, should be
       applied to the data either before or in this task.
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 UV file name (name).      Standard defaults.
  OUTCLASS...Output UV file name (class).     Standard defaults.
  OUTSEQ.....Output UV file name (seq. #).    0 => highest.
  OUTDISK....Disk drive # of output UV file.  0 => highest with space
  OPTYPE.....'SORC' => do one source at a time.  If > 1 source, then
             data will end up out of time order.
             Otherwise, do one scan at a time.  The result may be
             noisier but will beter reflect and real changes in the
             weights and the output data will still be in time order.
  SOURCES....Sources to be copied.   '  '=> all; if any starts with a
             '-' then all except ANY source named.
  QUAL.......Qualifier of sources to be copied. -1 => all.
  CALCODE....Calibrator code of sources to copy. ' '=> all.
  TIMERANG...Time range of the data to be copied. In order: Start day,
             hour, min. sec, end day, hour, min. sec. Days relative to
             ref. date.
  FREQID.....Frequency identifier to select (you may determine which is
             applicable from the OPTYPE='SCAN' listing produced by
             LISTR). This task does not use SELBAND or SELFREQ and is
             easily able to accomodate all Freq IDs.  <= 0 -> all
  SUBARRAY...Sub-array number to copy. 0=>all.
  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.
  FLAGVER....specifies the version of the flagging table to be applied.
              0 => highest numbered table.
             <0 => no flagging to be applied.
             Keep track of your FG table versions to be certain that
             you are using all of the flags that you intend to use.
  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.
             NOTE: SMOOTH IS FAIRLY DANGEROUS IN THIS CONTEXT.
             Applying SMOOTH because it was applied in BPASS must
             still be done.  SMOOTHING after BP application will
             smooth out real structure in the spectral shape of
             weights.  If you realy need SMOOTH to remove ringing from
             narrow-band signals, run SPLAT on the data to apply the
             SMOOTH and then set SMOOTH=0 for later work.  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).
  BIF........First IF included in operation
  EIF........Last IF included in operation
  ICHANSEL.. Array of start, stop, and increment channel numbers plus
             an IF used for channel selection in the averaging to
             compute a normalized rms.  Up to 20 sets if channels/IF may
             be entered.  The first having ICHANSEL(2,i) <= 0
             terminates the list.  ICHANSEL(4,i) is the IF number,
             with <= 0 meaning all IFs.  If an IF has no ICHANSEL set
             for it, then the inner 3/4 of the channels will be used.
  FPARM......(1) Number of times to be included in the time rms.  We
                 recommend an odd number and < 3 -> 3.
             (2) Normal interval between samples in seconds.  The
                 program will not do intervals longer than 2 *
                 FPARM(1) * FPARM(2).   0 -> 10 secs
                 IT IS IMPORTANT TO HAVE THIS ABOUT RIGHT.  If it is
                 too short, in particular, then data samples that
                 belong in the same bin (time interval) may end up in
                 different bins.  This happens most often when data
                 have been time averaged after selective flagging.
                 Set it to somewhat less than the averaging time -
                 if observations at XINT are averaged over N times,
                 set FPARM(2) = (N-0.5) * XINT.
             (3) Examine the data before doing any other checks and
                 flag all samples > FPARM(3) Jy.  0 -> 1.E8.
             (4) Code for type of smoothing function: 1: Boxcar,
                 2: Gaussian, 3: Exponential, 4: Linear, 5 Median
             .   0 -> 1
             (5) FWHM for Gaussian, exponential, linear in minutes.
                 0 -> 10
             (6) Full support size for smoothing function in minutes,
                 the function has value 0.0 outside +- FPARM(6)/2 from
                 the time being evaluated.  0 -> 10 for box, median;
                 0 -> 3, 4, 2 * FPARM(5) for Gaussian, exponential,
                 and linear, resp.
             (7) Minimum weight factor: the existing weight is
                 multiplied by 1/rms^2 so this is equivalent to
                 setting a maximum (normalized) rms.  0 -> 0.
             (8) Maximum weight factor: the existing weight is
                 multiplied by 1/rms^2 so this is equivalent to
                 setting a minimum (normalized) rms.  0 -> 10000.
                 NOTE: these minimum and maximum rms are applied
                 before the smoothing to keep really extreme values
                 from affecting the smoothed values excessively.
             (9) If > 0, average the rms values over polarization
                 before smoothing.
             (10) > 1 => ignore incoming data weights in averaging and
                         in writing the output
                  > 0 => set incoming weights to 1 before scaling them
                         on output but use them in averaging
                  <=0 => use incoming weights throughout
  FQCENTER,..>  0 => Change frequency axis reference pixel to
                     Nchan / 2 + 1
             else => do not change reference pixel
  BADDISK....The disk numbers to avoid for scratch files (sorting
             tables mostly).

EXPLAIN SECTION


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