[ASTRO\]UV_TRACKS station1 station2 [station3 [...]] [/FRAME
[size]] [/HOUR_ANGLE Hmin [Hmax]] [/TABLE [Name]] [/HORIZON Elmin] [/IN-
TEGRATION t] [/STATIONS ALL|list] [/WEIGHT Mode]
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
SIC LOG ASTRO_STATIONS GAG_ASTRO_DATA:astro_stations.dat)
---- 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.