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Description of Simulations
We have simulated the (u,v)
coverage on the VLA+PT link for a variety of different conditions.
The simulations assumed the VLA in its A configuration, with two
VLA antennas missing. The antenna in the middle of the southwest arm,
at AW5, has been taken out because its back-end hardware is used for
the Pie Town signal. The antenna in the middle of the southeast arm,
at AE5, is assumed to be used to replace Pie Town in the VLBA. For
the purposes of these simulations, an observing frequency of 8.4 GHz
has been used. Each sub-heading below contains a link to relevant plots
and files.
Full UV Coverages
Simulations
have been done for complete observations of sources from hour angles
of -6 hours to +6 hours, every 20 degrees in declination, from
-40 degrees to +80 degrees. At the lower declinations
the hour-angle coverage is reduced by the elevation limit of 8 degrees.
Synthesized beams, down to 5% of the peak, have been plotted for two
data weightings: full uniform weighting, and weighting with Briggs
robustness parameter=0, in between uniform and natural weighting.
No beams have been plotted for pure natural weighting, because this
gives relatively low weight to the Pie Town baselines.
Snapshots
A complete set of simulations of snapshots has not been done as the
one-dimensional nature of the long baselines to Pie Town provides rather
dreadful (u,v) coverage. However, it is possible to
get reasonably good (u,v) coverage and beam shapes by combining
a series of snapshots made at different hour angles. To provide a
sense of how well such snapshots will work, we have simulated observations
of a source at +40 degrees declination, consisting of
(i) one 5-minute
snapshot at transit
(ii) three 5-minute snapshots, at hour angles of
-4, 0, and +4 hours
(iii) five 5-minute snapshots, at hour angles of
-4, -2, 0, +2, and +4 hours, and
(iv) nine 5-minute snapshots, once per
hour from hour angles of -4 to +4 hours.
Do-it-yourself Simulations
All simulations have been
run with the AIPS task UVCON. Multiple snapshots have been
generated by running individual snapshots, and combining the data using
DBCON. If you would like to perform your own simulations for different
declinations, or different hour angle coverages, an input file
containing 25 VLA antennas (without AW5 and AE5) plus Pie Town is
available.
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National Radio
