As of Fri Jul 19 9:14:07 2024

VLBABPSS: Procedure to create BP table


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 #

                                   Data Selection
CALSOUR                            Bandpass calibrator sources.
CALCODE                            Calibrator code '    '=>all
TIMERANG                           Time range to select
ANTENNAS                           Antennas to select

                                   CLEAN map (optional)
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
CMODEL                             Model type: 'COMP','IMAG'
                                   'SUBI' (see HELP re images)
SMODEL                             Source model, 1=flux,2=x,3=y
                                   See HELP SMODEL for details.

                                   Control options
REFANT                             Reference antenna
BPASS5                             If not 0, set BPASSPRM(5) =
                                   BPASS5 ELSE SET IT 1.
                                   See help for details.

          VLBABPSS is defined in the VLBAUTIL run file.


Type: Procedure
Use:  VLBABPSS runs BPASS for VLBA data.

      This procedure is based on the recommendations laid out in VLBA
      Scientific Memo #37 (Craig Walker).  Run VLBAAMP after VLBABPSS.
      That procedure begins by running ACSCL to perform post-bandpass
      and delay amplitude corrections.  It then does the a-priori
      amplitude corrections with APCAL.

  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 bandpass response functions are
             to be determined.  All ' ' = all sources; a "-" before a
             source name means all except ANY source named. If the data
             file is a single-source file no source name need be
             specified.  If both IN2NAME and IN2CLASS are specified,
             but multiple sources are selected, BPASS will quit.
  CALCODE....Calibrators may be selected on the basis of the calibrator
                  '    ' => 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.
  TIMERANG...Time range of the data to be selected. In order: Start day,
             hour, min. sec, end day, hour, min. sec. Days relative to
             reference date.
  ANTENNAS...A list of the antennas for which bandpasses are to be
             determined.  If any number is negative then all antennas
             listed are NOT to be used and all others are.
The following specify a CLEAN model to be used if a single source was
specified in CALSOUR
  IN2NAME....Cleaned map name (name).      ' ' => no Clean model
             Note: a CLEAN image for only a single source may be given
             although the uv data 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).     ' ' => no Clean model
             If a Clean model is specified, then only one source may
             be selected (multi-source files) and no SMODEL may be
             specified (single-source files).
  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
                   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.......Only components > FLUX in absolute value are used in the
  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
             '    ' allows the program to use the fastest
             NOTE: when using a model derived from data with
             different 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.
             '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.....For single-source files only: a single component model to
             be used instead of a CLEAN components model; if SMODEL(1)
             > 0 then use of this model is requested.  Note that
             IN2NAME or IN2CLASS must be blank if SMODEL(1) > 0 and
             both must be specified if SMODEL(1) <= 0 for
             single-source files.
                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)
  REFANT.....The antenna to use as a reference in the least-squares
  BPASS5.....If 0, BPASSPRM(5) = 1.  If not zero, BPASSPRM(5)=BPASS5.
             HELP BPASS says:
             (5) Divide by channel 0 option. *** CHANGED MAY 2010 ***
                   In general, use 0.1 when using multiple calibration
                   sources.  ICHANSEL default is inner 75 percent.

                   If ~0 (-0.5 to 0.5,but not 0) the value of "channel
                   0" is determined and applied (divided into the data)
                   on a record-by-record basis, either from the average
                   of channels specified by ICHANSEL or from an external
                   file (if IN3NAME and IN3CLASS are specified).  If
                   -1 (-1.5 to -0.5), the same is done but the
                   amplitude of channel 0 is made 1.0 so a phase-only
                   correction is made.  Note that model division is
                   turned off if either of these options is selected.

                   If -2 (< -1.5), divide by the average of channels
                   specified by ICHANSEL (no external file) after the
                   time averaging.  This option allows a normalized
                   bandpass to be found correcting for any
                   uncalibrated variations in the continuum.  If you
                   have poor phase stability use 0 or -1, if you have
                   decent phase stability use -2.

                   If you have good phase stablility use +1.  Note
                   that division by channel 0 adds biased noise
                   because the channel-averaged amplitude is by its
                   very nature biased;  the -2 option should be less
                   biased since the data have been vector averaged in
                   time first and so are less noisy. The -1 (phase
                   only) division should avoid the amplitude bias but
                   then the banddpasses are not normalized.  That can
                   be corrected later with BPASSPRM(10) options.

                   If > 0.5, do no normalization before determining the
                   solutions.  This requires good stability during
                   each integration period.  BPASSP(10)=3 still allows
                   a normalized solution which may be even less biased
                   since it is on an antenna rather than a baseline

                   Note also that a channel 0 may not be determined
                   sensibly if the phase changes a lot across the pass
                   band except by setting ICHANSEL to select a very few

                   ********  Note, if normalization is not done on a
                   record-by-record basis, users must be very careful
                   about averaging different calibration sources.  Any
                   channel-dependent flagging will cause the different
                   sources to be differently weighted in the partly
                   flagged channels than in the completely unflagged
                   ones.  The shape of the bandpass in this case will
                   not be correct.  Therefore, if channel-dependent
                   flagging is done and multiple calibrators averaged,
                   the normalization must be done on a record basis.


VLBABPSS:  Procedure to determine antenna bandpass functions from
           calibrator data
Documentor:  Amy Mioduszewski
Related Programs: BPASS

This procedure is defined in VLBAUTIL.

VLBABPSS determines the bandpass calibration using BPASS.

VLBABPSS should be used along with VLBACCIR and VLBAAMP instead of
VLBACALA.  This redesign of the amplitude calibration path is based on
VLBA Scientific Memo #37 (Craig Walker).  The new recommended steps for
amplitude calibration are:
  1) Do preliminary calibration steps that are necessary (e.g., VLBAFIX,
  2) VLBACCOR -- digital sampling corrections
  3) VLBAMPCL (or VLBAPCOR) -- remove instrumental delay
  4) VLBABPSS -- do bandpass
  5) VLBAAMP -- correct auto-correlations and a priori amplitude calibration
  6) Continue with calibration.