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.