As of Fri Jul 19 8:37:07 2024

HOLOG: Task to read and process holography visibility data


                                   Input data file name.
OUTNAME                            Output image name.
OUTDISK         0.0         9.0    Output disk number.
UVTAPER         0.0                Data tapering: (1) type,
                                   (2) width in cells to 0.5
OPTYPE                             Telescope type: 'PFOC' prime
                                   focus, 'SUBR' subreflector
                                   'SURP' subreflector with
                                   reference pointing
FACTOR          0.0       100.0    Magnification: 0 -> 13
OFFSET          0.0       100.0    Distance from prime focus to
                                   bottom subreflector 0->0.512
REFREQ          0.0                Reference frequency in GHz
APARM                              Operating parameters.
                                    1: Frequency (GHz).
                                    2: Satellite elevation, deg.
                                       Use 0 for sidereal obj.
                                    3: Antenna diameter, m.
                                    4: Unpaneled diameter, m.
                                       (3,4) used to blank ant.
                                       aperture phase data.
                                    5: Focal length, m.
                                    6: Slope in SURP 0 -> 0.65
                                    7: Disabled
                                    8: Disabled
                                    9: 10000 * Ref ant. +
                                       100 * target ant. + IF#.
                                    10: Stokes (RR=1, LL=2)
                                       (9) and (10) used only
                                       if INFILE is not of form
CELLSIZE                           Cell size in asec for output
                                   image type 1-3.  Resets
BPARM                              Data reduction parameters.
                                    1: Required map size, meters
                                       or use CELLSIZE
                                    2: No. of pixels on a side
                                       of the output map (power
                                       of 2, min=32, max=1024).
                                       0 => 128
                                    3: Min. antenna scan angle
                                       Units: inverse sine(ang)
                                       0 => all data used.
                                    4: Max. antenna scan angle
                                       Units: inverse sine(ang)
                                       0 => all data used.
                                       <0 => radial (min, max).
                                    5: Amplitude scaling factor
                                       0 => 1
                                    6: Fourier transform sign
                                       0 => -1 (VLA convention)
                                       2, -2 -> DFT
                                    7: Minimum antenna aperture
                                       used for fit, in meters
                                       < 0 => circular min.
                                       0 => set by APARM(4)
                                    8: Maximum antenna aperture
                                       used for fit, in meters
                                       < 0 => Circular max.
                                       0 => set by APARM(3)
                                       (7,8) used for focus and
                                       pointing calculations.
                                    9: Correction control flags:
                                       read the HELP!
                                    10: >0 => logarithmic ampl.
                                        .LE. 0 => linear ampl.
                                       default = linear
CPARM                              Parameters for the gridding
                                   operation (see HELP).
OTFMODE        -1.0      20.0      If OTF data, sum OTFMODE
                                   records together before use.
NORMALIZ       -1.0       1.0      > 0 => normalize outputs 1
                                   and 2 below
DOVECT         -1.0       1.0      > 0 write real/imaginary not
                                   amplitude/phase images
DPARM                              Output maps, >0 => Save this.
                                    1,2: Regridded amplitude and
                                         phase of the observed
                                         antenna beam pattern.
                                      3: Weights used in the
                                         regridding procedure.
                                    4,5: Derived amplitude and
                                         phase of the antenna
                                    6,7: Amplitude and phase of
                                         the point-spread func.
                                      8: Focus model corrections
                                      9: Surface deviation map.
                                     10: Antenna power pattern
                                         and phase (See HELP!)
VPARM                               Use this model don't fit
                                    1. Constant offset degrees
                                    2. Phase ramp in X deg/cell
                                    3. Phase ramp in Y deg/cell
                                    4. Feed/subreflector offset
                                       in X in mm
                                    5. Subreflector/Feed offset
                                       in Y in mm
                                    6. Subreflector/Feed offset
                                       in Z in mm  (focus)
                                    7. Subreflector X tilt deg
                                    8. Subreflector Y tilt deg
                                    9. Cassegrain feed offset
                                       in X mm
                                    10. Cassegrain feed offset
                                       in Y mm
                                    11. > 0 replace phase with
                                    12. > 0 Replace amp with
                                       average, value is clip
                                       level (all below set 0)


Type: Task
Use:  HOLOG processes holography data.  It reads visibility data
      from a file and Fourier transforms it to produce the
      grading in the aperture plane of the antenna.  Up to nine
      different AIPS image files will be produced according to
      the options specified in DPARM.

      In the following description, (l,m) are the angular antenna
      offsets, while (u,v) are distances in the antenna aperture

      The input data format is four free format ASCII encoded
      values per record:
          1) Azimuth offset from source (degrees)
                or true l (if APARM(2) <= 0)
          2) Elevation offset from source (degrees)
                or true m (if APARM(2) <= 0)
          3) Amplitude (Volts or dB) or Real (Volts)
          4) Phase (degrees) or Imaginary (Volts)

  INFILE......Input visibility file name in the form AREA:FILE, where
              AREA is a directory logical name or environment
              variable, and FILE is an operating system specific file
              name.  If INFILE = 'ANT' or is blank, then INFILE will
              be set to
              where nn is the moving antenna number and mm is the
              reference antenna number (= 0 if more than one reference
              antenna is used), ss is the Stokes, and ii is the IF.
              If INFILE contains only a logical name, as INFILE =
              'AREA:', then 'AREA:HOLOnn-mmssii' will be used. The
              values of nn, mm, ss, and ii come from APARMs (9) and
  OUTNAME.....Output image name (12 characters).  If the last 7
              characters are blank, they are set to 'nn-mmss'.
  OUTDISK.....Output disk number.
  UVTAPER.....Tapering of data during the gridding process:
              (1) Type: 1 Gaussian, 2 Exponential, 3 Linear
              (2) Radius in cells for taper of 0.5.  0 => N/3.
              (Remember that the max radius of the data must be
              < N/2 just to avoid aliasing.)
  OPTYPE......The model used for removing the effects of primary focus
              offset.  'PFOC' = Prime Focus. 'SUBR' = Cassegrain
              system.  'SURP' = Cassegrain system with reference
              pointing  - default SUBR
  FACTOR......The magnification.  Used only if OPTYPE = 'SUBR', 'SURP'
  OFFSET......The distance between the prime focus and the bottom of the
              subreflector in meters.  Otherwise known as c-a where 2c
              is the distance between the 2 hyperbolic foci and a is the
              distance between the y-axis intercept of the upper
              hyperboloid from the midpoint of the 2 foci in meters.
              0 -> 0.522  appropriate for the VLA.
              Used only with tilt parameters to display tilts in
              degrees rather than physical offsets and only with
              subreflector OPCODEs.
Operating parameters: all are required (NO defaults).
  REFREQ......Use this as the reference frequency in GHz.  If 0, use
              the observing frequency found in the UVHOL output file
              (INFILE here).
  APARM(1)....Observing frequency (GHz). (ignored)
  APARM(2)....Satellite elevation, degrees. Set = -1. for VLA data
              (true l,m); set = +1. for sky az,el; set = actual
              elevation for true az,el
  APARM(3)....Antenna diameter, in meters. Used to blank antenna
              surface phase map before applying models.
  APARM(4)....Subreflector or unpaneled diameter, in meters.  Used to
              blank antenna phase map before models are applied.
  APARM(5)....Focal length, in meters.  This is used in correcting for
              the focus and feed offset, and in computing the surface
              deviation map.
  APARM(6)....In SURP only, the slope applied to "q".  0 -> 0.65
  APARM(9)....10000 * Reference antenna number + 100 * 2nd (moving)
              antenna number + IF number.  Used only for default names
              (i.e., if INFILE = 'AREA:')
  APARM(10)...Stokes ID (1 - 4 => RR, LL, RL, LR).  Used only for
              default names (i.e., if INFILE = 'AREA:')
Data reduction control parameters.
  CELLSIZE....Cell size in asec for output image types 1, 2, and 3.
              If > 0, BPARM(1) is reset to Lambda / (CELLSIZ(1) * AS2RAD)
  BPARM(1)....Required map size, in meters. or use CELLSIZE
  BPARM(2)....Number of pixels on a side of the output map
              (power of 2, maximum 1024).
  BPARM(3,4)..Range of |l| and |m| (antenna scan angles) to use for
              transform. Units are inverse sine(angle)
  BPARM(5)....Scaling factor for the input amplitudes.
  BPARM(6)....Fourier transform control.  If negative, the phase read
              from the data file is negated.  If the absolute value is
              2, a direct Fourier transform will be done, otherwise,
              an FFT.
  BPARM(7,8)..Range of |x| and |y| used in correcting for pointing,
              focus, and feed offset.  Negative values give (min, max)
              of r = SQRT(u*u + v*v).  See also BPARM(9).
  BPARM(9)....Decimal encoded control parameters
                  1: If set, apply the subreflector tilt model.
                 10: Turn off phase slope model (pointing).
                100: Inhibit local phase ambiguity correction in
                     the antenna aperture (V_PHA) plane.
               1000: Turn off all model calculations.
               2000: Turn off subreflector offset model.
               4000: Turn off focus (z) model.
               8000: Turn on Cassegrain feed offset model
  BPARM(10)...Switch for logarithmic or linear data
              >= 0 for logarithmic data (as for PKS)
              < 0  for linear data (for the VLA).
Regridding parameters.
  CPARM(1)....Type of interpolation to apply in gridding 'l'.
                1: Pillbox, (don't use for regularly sampled data)
                2: Exponential,
                3: Sinc,
                4: Sinc*Exponential,
                5: Spheroidal (default).
              NEGATE to obtain natural weighting. (default = uniform)
  CPARM(2)....Support radius in u, in cells.
  CPARM(3-5)..Parameters defining the interpolation function
              in 'l'.
                Do HELP UVnTYPE for n=1,2,3,4,5.
  CPARM(6-10).Corresponding parameters for 'm'.
  OTFMODE.....If time averaging (actually summing over intervals) is
              useful (only in OTF mode), sum OTFMODE records together
              before using them in the imaging.
Output option flags.
  NORMALIZ....> 0 => amplitude and phase will be normalized, else no
              normalization of amplitude and phase is done.
  DOVECT......> 0 -> write real and imaginary rather than amplitude
                     and phase on DPARM(1,2)
  The particular map will be stored if the associated DPARM is
  > zero.  If all are <= 0, DPARM(4,5) will both be set to 1.
  AIPS task PANEL wants (4) for the mask and (9) for the deviations.
  DPARM(1,2)..Regridded amplitude and phase of the observed antenna
              beam voltage pattern (A_AMP, A_PHA).
  DPARM(3)....Weights used in the regridding procedure (WGT) -
              includes the weights for uniform (vs natural) weighting.
  DPARM(4,5)..Derived amplitude and phase of the illumination of the
              antenna aperture (V_AMP, V_PHA). The focus model, if
              requested, will be removed from the phase image.
  DPARM(6,7)..Amplitude and phase of the point-spread function.  This
              indicates the blurring in the derived grading map
              (P_AMP, P_PHA).
  DPARM(8)....Map of the phase corrections removed by the focus model
  DPARM(9)....Map of the surface deviations of the antenna (V_DEV).
              Units are in meters. The focus offset model, if
              requested, will be removed.
  DPARM(10)...The interpolated antenna power pattern (A_PWR).  Set it
              = to the desired interpolation factor, with anything >0
              and < 2 => 2.  Must be a power of 2 <= 2048 / NPIX,
              where NPIX = BPARM(2).  The phase image (A_PHS) is also
              written out.
Compute a model rather than fitting one:
If any of VPARM(1) through VPARM(8) is not zero, then a model image is
computed from the parameters in VPARM rather than being fit to the
data in INFILE.  Different models are computed for the 3 values of
  VPARM(1)....Constant phase offset in degrees
  VPARM(2)....Phase ramp in X in degrees/cell - equivalent to a
              pointing error in X in arc minutes
  VPARM(3)....Phase ramp in Y in degrees/cel - equivalent to a
              pointing error in Y in arc minutes
  VPARM(4)....Feed offset in X in mm for PFOC
              Subreflector offset in X in mm for SUBR, SURP
  VPARM(5)....Feed offset in Y in mm for PFOC
              Subreflector offset in Y in mm for SUBR, SURP
  VPARM(6)....Feed offset in Z in mm for PFOC
              Subreflector offset in Z in mm for SUBR, SURP
  VPARM(7)....Subreflector tilt in X in degrees
  VPARM(8)....Subreflector tilt in Y in degrees
  VPARM(9)....Cassegrain feed offset in X in mm
  VPARM(10)...Cassegrain feed offset in Y in mm
  VPARM(11)...> 0 => replace phase with model
  VPARM(12)...> 0 => replace amplitude with average amplitude if
              amplitude > VPARM(12), else set amplitude to 0.  The
              amplitude is a weighting function in the the determination
              of rms, forward gain, and beam pattern.