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SOLVE HOLOGRAPHY

      CLIC\SOLVE HOLOGRAPHY [NPOINTS npix] [FREE r1 r2 ...]
      [MODES nmodes] [ITER niter gain] [MASK npanels p1 p2 p3 ...]
      [BASELINES b1 b2 b3 ... ]
      [DISTANCE dist] [DIAMETER diam] [DEFOCUS df]
      [TEST testFile] [FRESNEL] [ASTIGMATISM]
      [/PLOT [AMP amin amax astep] [PHA pmin pmax pstep]
      [ERRORS emin emax estep]  [NUMBER]] [/OFFSET x y z]


  This command computes an antenna surface map from a set of holography mea-
  surements.  The set of scans (procedure HOLO) should have first been cali-
  brated in phase, amplitude and RF passband relative to interspaced  corre-
  lation  scans  in  the  direction of the source.  The map will be computed
  from the first band and subband sets chosen with commands SET BAND and SET
  SUBBAND.  SET BAND AVERAGE is recommended for continuum measurements; only
  continuum subbands should be used. For line  measurements,  the  continuum
  width  of  one  of the correlator units should match the actual line width
  for better sensitivity.  The antenna to be studied should be  selected  by
  command  SET  ANTENNA  i.   Data  from  the baselines linking this antenna
  (scanned) to other (fixed) available antennas are averaged.


  SOLVING FOR ANTENNA PARAMETERS

  The amplitude and phase maps are obtained by FFT of the observed beam map.
  The maps will be square (npix by npix pixels). The default for npix is 64,
  it should be greater than the number of observed holography scans (usually
  16 or 32).

  After  FFT  a  gaussian illumination function is fitted in the amplitudes,
  giving the offset from the center (in meters) and the edge taper (in  dB).
  If /PLOT is given, the amplitude map will be displayed (in decibels), from
  -15 to 0 dB, with contours in steps of 3db (these  may  be  changed  using
  "/PLOT AMP amin, amax and astep").

  A  least  square  fit is used to correct the phases from a remaining phase
  offset, pointing errors, and focus offsets. The panel rings following  the
  keyword  FREE  are  not  used for this fit. If /PLOT is given, the antenna
  normal surface errors will be shown, in micrometers, from -500 to 500 mum,
  with  contours  in steps of 100 mum (these may be changed using "/PLOT ER-
  RORS emin, emax and estep"). If /PLOT PHASE is given, the  residual  phase
  map  will be plotted instead of surface errors, in radians from -pi to pi,
  with contours in steps of 0.2 radian. If this  map  shows  remaining  2*pi
  discontinuities, or if focus offsets larger that 1mm are found, you should
  try using option /OFFSET to correct the phases for an offset (x,y,z in me-
  ters) in the focus coordinates, before fitting. This should lead to better
  rms values.

  The rms values for the phase and the normal surface errors (in radians and
  micrometers)  are  given,  both  with and without amplitude weighting. The
  contribution of the illumination amplitude distribution  and  of  the  ob-
  served phase errors to the antenna efficiency are given.

  A  gildas  image file of the results is kept (e.g. "jj-mmm-yyyy-an1.map"),
  in which plane 3 in the amplitude in dB, plane 4 the raw phases and  plane
  2  the  residual  phase in radians (plane 1 contains the fitted amplitude,
  i.e.  a Gaussian).


  SOLVING FOR PANEL DISPLACEMENTS

  Finally, if "PLOT MODE nmodes" is entered with nmodes  larger  than  0,  a
  listing  of  panels  displacements  is  computed.  This uses the parameter
  nmodes which is the number of modes used for each panel: 1 is the transla-
  tion mode only (normal to the antenna surface); 3 (the usual setting) adds
  both tilt modes, radial and tangential, but no panel deformation; 4 adds a
  torsion  mode  and  5  a  motion of the panel center relative to its edges
  (there are only 5 screws for each panel, thus only 5 possible modes).

  The results of this computation is written in a file "panels-an1.dat"  (or
  similar  name  for other antennas). In this file, a line for each panel is
  printed. The first two numbers are the panel numbers, followed  by  up  to
  five  screw  settings  (three only for the inner ring). All screw settings
  are equal if nmodes was set to 1, only one number is then printed.

  The fit is obtained iteratively: the panel  orthogonal  deformation  modes
  are computed from the aperture phase, then the phase change that these de-
  formations would have caused is computed (by doing a FFT to the beam  map,
  doing  a  cut-off  at the observed map size, followed by a FFT back to the
  aperture plane), and subtracted from the aperture phase; second order pan-
  el  deformations  are computed from these residuals, and so on. The number
  of iterations niter and a gain to this iterative procedure may  be  speci-
  fied  (ITER  niter  gain); their default values are 5 and 1.0 . Use ITER 0
  for no iterative procedure at all. At each step the phase residual rms and
  the rms of panel deformations fitted are given (weighted by the fitted am-
  plitude illumination and counted perpendicularly to the surface).

  Variables containing antenna parameters are available:
    -TAPER_X, TAPER_Y: illumination tapers.
    -OFFSET_X, OFFSET_Y: illumination offsets.
    -RMS_PHA_U, RMS_PHA_W: phase r.m.s (unweigthed or weighted by  illumina-
      tion).
    -ETA,  ETA_230, ETA_345: aperture efficiency at observing frequency, 230
      and 345 GHz.
    -JYKEL, JYKEL_230, JYKEL_345: antenna efficiency at observing frequency,
      230 and 345 GHz.
    -HOLO_FOCUS: focus position.
    -HOLO_RMS: surface r.m.s. (unweighted or weighted by illumination).
    -HOLO_RING: rings r.m.s

  SOLVE HOLOGRAPHY options

  SOLVE HOLOGRAPHY NPOINTS npix

      Gives the number of pixels of the amplitude and phase maps. Default is
      64.

  SOLVE HOLOGRAPHY MODE nmodes

      Force CLIC to compute the panel displacements (see above).  nmodes  is
      1 to 5.

  SOLVE HOLOGRAPHY ITER niter gain

      Select  the number of iteration and gain to be used for the panel dis-
      placement determination (see above). Does make sense only if  used  in
      conjonction with the MODES keyword.

  SOLVE HOLOGRAPHY BASELINES b1 b2 b3 ...

      By  default,  all  baselines connecting the antenna to be studied (se-
      lected by SET ANTENNA) to a fixed antenna are used. The keyword  BASE-
      LINES allows to specifically select the baselines to be used.

  SOLVE HOLOGRAPHY MASK npanels p1 p2 p3 ...



  SOLVE HOLOGRAPHY FREE r1 r2 ...

      Indicates the ring NOT to be used for paraboloid fit.

  SOLVE HOLOGRAPHY ASTIGMATISM NOFOCUS NOXYFOCUS FOCUS


  SOLVE HOLOGRAPHY POINTING FUDGE CHEAT DEFOCUS df DIAMETER



  SOLVE HOLOGRAPHY TEST testFile

      Use a test beam file instead of real data from the CLIC data file.

  SOLVE HOLOGRAPHY DISTANCE dist

      Gives distance of the source, in meters. Not relevant for astronomical
      sources, of course. Any distance larger than than 1000  km  (which  is
      the default) forces the FRESNEL approximation.

  SOLVE HOLOGRAPHY FRESNEL


      Use Fresnel approximation (use only the Fourier transform, neglect the
      additional terms in the complex exponential argument). This is the de-
      fault  mode for long distance (e.g. astronomical) sources, but must be
      indicated if a DISTANCE has been entered.

  SOLVE HOLOGRAPHY /OFFSET x y z



  SOLVE HOLOGRAPHY /PLOT [AMP amin amax astep] [PHA pmin pmax pstep] [ERRORS
  emin emax estep] [NUMBER]

      With /PLOT, SOLVE HOLOGRAPHY will plots the results: two maps are dis-
      played, which by default are the amplitude illumination  pattern  (de-
      fault  plot  limits  are  -15dB to 0dB by step of 3dB) and the antenna
      normal surface errors (from -500 to 500 mum, with contours in steps of
      100  mum).  The  min.,  max., and steps can be changed with "/PLOT AMP
      amin amax astep" and "/PLOT  ERRORS  emin  emax  estep".  With  "/PLOT
      PHASE", the phase residuals are plotted instead of the surface errors.
      Default are from -pi to +pi by step of 0.2 radians.

      If NUMBER is given as a /PLOT argument, the panels numbers are  drawn.


Gildas manager 2011-04-01