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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
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
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
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
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
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-
-ETA, ETA_230, ETA_345: aperture efficiency 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
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 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 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