next up previous contents index
Next: SOLVE DELAY Up: SOLVE Previous: SOLVE AMPLITUDE   Contents   Index


SOLVE BASELINE

        CLIC\SOLVE BASELINE [/OFFSET b1 dx1 dy1 dz1 b2  ...]
        [/SEARCH range] [/POLYNOMIAL degree]

    This uses a linear method to determine baselines. The  baselines  to  be
    determined  must have been selected by the SET BASELINE command, and the
    data plotted; plot axes must have been previously selected by  :  SET  X
    HOUR_ANGLE  DECLINATION  and SET Y PHASE. With SET ANTENNA in action the
    antenna position offsets are directly fitted to the antenna phases,  en-
    suring baseline closure.

    The  fitting  should  work only if the starting values are within half a
    wavelength in any direction of the true values. Use  option  /OFFSET  to
    correct  the  phases  for  an offset (dx1,dy1,dz1) in baseline b1 before
    fitting.  This is needed if the baseline was wrong by more than  half  a
    wavelength. Offsets are to be given in meters.

    The  results  are  given  as  offsets in  meters  to  be  added  to  the
    baseline  used  for  data  acquisition (which may be read by SIC\EXAMINE
    BASELINE).  The total fitted baseline is also given in meters,  as  well
    as  the  rms  of  the residuals in phase units.  Two sets of offsets are
    given:  the first set (dx, dy, dz) are the offsets with respect  to  the
    antenna  positions actually used, while the secoond set (DX, DY, DZ) are
    with respect to the standard antenna coordinates (the default values  in
    OBS).

    The /SEARCH option  enables  an  automatic  search  with  starting  off-
    sets  scanning a 3-d box in dx, dy, dz, by steps of half a wavelength in
    the three directions.  The argument range is in  meters   (scanning   is
    from  -range/2 to +range/2, default -0.005 to 0.005).  Only the solution
    with the minimum rms is kept.

    With option /POLYNOMIAL degree, and  if  SET  X  TIME  is  used  in  ad-
    dition  of  HOUR_ANGLE and DECLINATION, a polynomial function of time is
    included in the phase function being fitted.  The degree may range  from
    0 (the default) to 3.  In that case command RESIDUALS will also plot the
    residuals as a function of time.

    Use command RESIDUALS BASELINE  to  display  the  fit  residuals  (phase
    should be constant). Use later command PRINT BASELINE to create a proce-
    dure file (named CLIC-BASELINE.OBS) containing the antenna position off-
    sets.   This procedure file may be executed by the observing program OBS
    on the control computer bure01.

    If one specify elevation  as  an  additional  X  variable  (e.g.  SET  X
    HOUR_ANGLE  DECLINATION TIME ELEVATION), then an additional parameter is
    fitted: the offsets between elevation and azimuth axes  (or  rather  the
    differences between antennas). These differing offsets result in a phase
    effect proportional to the cosine of elevation. In antenna  mode,  these
    offsets  are  given  for  each antenna in meters. In baseline mode, only
    differences are computed. To further correct for  this  effect  use  the
    command MODIFY AXES.


Gildas manager 2019-02-18