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        [ASTRO\]UV_TRACKS   station1   station2  [station3  [...]]   [/FRAME
    [size]] [/HOUR_ANGLE Hmin [Hmax]] [/TABLE [Name]] [/HORIZON Elmin] [/IN-

    Plot  interferometer  UV tracks as observed with the Plateau de Bure in-
    terferometer (but the command is in fact more general and  can  be  used
    with any array, especially ALMA: see bottom of this help).

    Station  coordinates  are  searched  for  in the file defined by the AS-
    TRO_STATIONS logical variable. Stations  should  be  referred  to  by  a
    mnemonic (e.g. E03, W00 ...) given as arguments of UV_TRACKS.

    The  coordinates of the most recently selected SOURCE or PLANET are con-
    sidered. Option /HORIZON specifies a minimum elevation (in degrees)  for
    the  source. Option /HOUR_ANGLE can be used to limit the hour angle cov-
    erage. Default is from source rise  (above  the  minimum  elevation)  to
    source setup; Hmin and Hmax are in hours.  The frequency of the simulat-
    ed observation is read in the FREQUENCY SIC variable (which is also used
    by several other commands in ASTRO).

    UV_TRACKS  can be used iteratively, to simulate the observations of sev-
    eral configurations. Option /FRAME [size] should be used to start a  new
    UV  coverage. It clears the plot, draws the box, and open a new table if
    /TABLE is present. 'size' is the maximum UV spacing plotted,  in  meters
    (default  800  m).  Subsequent call to the command (without /FRAME) adds
    the new configurations. The user may select another color  pen  to  dis-
    tringuish  between the various coverages. A sketch of the interferometer
    described by ASTRO_STATIONS is also drawn, and the selected stations/an-
    tennas are highlighted.

    Option  /TABLE  can be used to write the sampling function (UV coverage)
    in a UV table for further processing such as producing beams  using  the
    task  UV_MAP.  Name  should  be specified only if option /FRAME has been
    used, to initialize the table. Subsequent call to the  UV_TRACK  command
    will  append the new observation to this table. The visibilities written
    in the UV table are constant, as if a point source were  observed  (real
    part  = 1, imaginary part = 0). The weight is by default constant, equal
    to 1. This can be modified using the /WEIGHT Mode option.  Mode  can  be
    UNIFORM (constant weight) or AIRMASS (weight proportional to airmass^-2,
    i.e. to sin(elevation)^2).

    Option /INTEGRATION t [min] is used to change the time interval  between
    points  in the UV plane (currently there is a max of 3000 points between
    HA_MIN and HA_MAX). Default is 15 minutes per point.

    ---- Notes for experts ----

    Option /STATIONS enable to access stations by their rank number  in  the
    ASTRO_STATIONS  file, rather by their mnemonic. ALL means 'take all sta-
    tions'. Switching between files describing interferometer  stations  can
    be  done  inside ASTRO by redefining the ASTRO_STATIONS logical variable
    using the command
    SIC LOG ASTRO_STATIONS "path/to/the/desired/file"
    The BURE stations are described in the file ephemeris/astro_stations.dat
    (and accessed by default on most ASTRO installs, or otherwise by

    ---- Using UV_TRACKS for ALMA ----

    UV_TRACKS can be used to simulate ALMA observations, using the very same
    options as described above (e.g. to create tables with  one  or  several
    configurations). To do so, the command sequence must be

    observatory alma
    sic log astro_stations "alma-cycle1-1.cfg"
    uv_track all [...options...]

    The  logical  astro_stations must point to a configuration file of ALMA.
    They are  distributed  with  GILDAS  and  are  called  "alma-cycle0-com-
    pact.cfg"   and   "alma-cycle0-extended.cfg"   for  Cycle  0;  "alma-cy-
    cle1-*.cfg" (6 different configurations) and "aca-cycle1.cfg" for  Cycle
    1.  Then "uv_track all" means all stations will be used. This is differ-
    ent from Bure, where all stations are in one single file  and  the  user
    defines  with  uv_track which stations are to be used; but this would be
    painful for ALMA (32 stations to enter in Cycle 1...).

    For ACA, it is better to enter "observatory aca" - coordinates  are  the
    same, but this will make sure the proper antenna diameter is used in the
    computation of shadowing.

Gildas manager 2014-07-01