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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 [ANGLE astangle]]
        [/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
    measurements. The set of scans (procedure HOLO) should have  first  been
    calibrated  in  phase, amplitude and RF passband relative to interspaced
    correlation scans in the direction of the source.  The map will be  com-
    puted from the first band and subband sets chosen with commands SET BAND
    and SET SUBBAND. SET BAND AVERAGE is recommended for continuum  measure-
    ments;  only  continuum  subbands should be used. For line measurements,
    the continuum width of one of the correlator units should match the  ac-
    tual  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 deci-
    bels), 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 an-
    tenna 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 ERRORS 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 meters) 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
    observed 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 am-
    plitude, 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 trans-
    lation  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 pan-
    el  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
    deformations 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  or-
    der panel deformations are computed from these residuals, and so on. The
    number of iterations niter and a gain to this iterative procedure may be
    specified  (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 residu-
    al  rms  and the rms of panel deformations fitted are given (weighted by
    the fitted amplitude 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 illumi-
        nation).
      -ETA, ETA_230, ETA_345: aperture efficiency  at  observing  frequency,
        230 and 345 GHz.
      -ETA_I, ETA_S: illumination and feed taper efficiency.
      -RUZE, RUZE_230, RUZE_345: ruze factor at observing frequency, 230 and
        345 GHZ
      -JYKEL, JYKEL_230, JYKEL_345: antenna efficiency at observing frequen-
        cy, 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
        displacement 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
        BASELINES 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 [ANGLE astAngle] NOFOCUS NOXYFOCUS FOCUS

        Options  for  fitting. With keyword ANGLE, SOLVE HOLOGRAPHY ASTIGMA-
        TISM uses a forced astAngle (in degrees) for astigmatism orientation
        and fits only astigmatism r.m.s.

    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 astronomi-
        cal 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  default 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]  [ER-
    RORS emin emax estep] [NUMBER]

        With  /PLOT,  SOLVE  HOLOGRAPHY will plots the results: two maps are
        displayed, which by default are the amplitude  illumination  pattern
        (default plot limits are -15dB to 0dB by step of 3dB) and the anten-
        na 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 sur-
        face 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 2019-01-23