SOLVE HOLOGRAPHY

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SOLVE HOLOGRAPHY

            CLIC\SOLVE HOLOGRAPHY [NPOINTS npix]
            [FREE [RINGS r1 r2] [SECTOR s1 s2]]
            [MODES nmodes]
            [ITER niter gain]
            [MASK npanels p1 p2 p3 ...]
            [BASELINES b1 b2 b3 ... ]
            [POINTING x1 y1]
            [REFERENCE a1]
            [DISTANCE dist]
            [DIAMETER diam]
            [DEFOCUS df]
            [TAPER t]
            [FOCUS df]
            [TYPE ASDM|VERTEX|AEC|MELCO12_1|MELCO12_2|MELCO12_3|BURE|IRAM30]
            [TEST testFile]
            [FRESNEL]
            [NOFOCUS]
            [NOXYFOCUS]
            [ASTIGMATISM [ANGLE astangle]]
            [APODIZE]
            [NOFEED]
            [BEAM SIGNAL|REFERENCE]
            [RIGGING e1 e2]
            [TEMP_BIAS t]
            [FIXSPACING s]
            [/PLOT [AMP amin amax astep] [PHA pmin pmax pstep]
            [ERRORS emin emax estep]  [NUMBER]]
            [/OFFSET x y z]
            [/THRESHOLD microns [nsigma]]

        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 ...

            Allows to mask some panels.

        SOLVE HOLOGRAPHY REFERENCE a1

            Allow to select a reference baseline (ALMA specific)

        SOLVE HOLOGRAPHY FREE [RINGS r1 r2] [SECTOR s1 s2]

            With keyword RINGS, indicates the ring NOT to be used for paraboloid
            fit.  With keyword SECTORS, indicates the sectors NOT to be used for
            paraboloid fit.

        SOLVE HOLOGRAPHY ASTIGMATISM [ANGLE astAngle]

            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 NOFOCUS NOXYFOCUS

            Options for fitting. With keyword NOFOCUS, no attempt is made to fit
            the  focus. With keyword NOXYFOCUS, only the z component of focus is
            fitted.

        SOLVE HOLOGRAPHY FOCUS f

            Allows to speficy value of focus (in m).

        SOLVE HOLOGRAPHY POINTING p1 p2

            Allow to add pointing corrections in case the coordinates stored  in
            the data file are wrong.

        SOLVE HOLOGRAPHY DEFOCUS df

            Allow  to  introduce  known  defocus (useful for near-field measure-
            ments).

        SOLVE HOLOGRAPHY TAPER t

            Allow to set the value of the illumination taper at the edge of  the
            primary (power).

        SOLVE HOLOGRAPHY DIAMETER d

            Sets antenna diameter to d.

        SOLVE HOLOGRAPHY TEST testFile

            Use  a  test  beam file instead of real data from the CLIC data file
            (must be a gdf .beam 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 TYPE BURE|IRAM30

            Allow to force an antenna type.

        SOLVE HOLOGRAPHY APODIZE

            Do  an  apodization  of the beam map (quadratic, down to zero on map
            edges).

        SOLVE HOLOGRAPHY BEAM REFERENCE

            Allows to do just the gridding of a  reference  beam  (exits  before
            FFT).  This  is  useful for special holography receivers that have a
            signal and reference beam.

        SOLVE HOLOGRAPHY /OFFSET x y z

            Introduce a focus offset (in m) around which the  solution  will  be
            searched.

        SOLVE HOLOGRAPHY /TRESHOLD microns [nsigmas]

            Use a cutoff threshold in absolute value of displacement and/or num-
            ber of sigmas for listing screws in panel adjustements. If only  one
            value  is  given,  this is the threshold in microns. For a threshold
            only in sigmas, use /THRESHOLD 0.0 nsigmas. Defaut is 0.0, 0.0.

        SOLVE HOLOGRAPHY RIGGING [e1 e2]

            Correct for gravitational deformations from the average of  the  two
            elevations e1 and e2 (default 20 and 90 degrees).

        SOLVE HOLOGRAPHY TEMP_BIAS t

            Correct for the thermal deformations between ambiant temperature and
            bias temperature t.

        SOLVE HOLOGRAPHY FIXSPACING s

            Set the spacing used for gridding.

        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.