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After solving for antenna-based gain solutions (based on QSOs),
one might realize that the gain corrections in amplitude
are lower for some antennas due to some reasons (such as larger pointing
errors, larger coherence loss and etc.). One might want to include
those factors in the visibility weighting in the imaging process
in addition to
the visibility variance calculated based on the systemp temperature, bandwidth,
and integration time. The Miriad smarewt
provides a software tool to calculate the mean values
of antenna gains in amplitude and multiply the visibility
variances by the mean antenna gains. The re-scaled visibility
variances can be used as the weights in the imaging process.
Here is an example of usage:
vis = uvdata_rx0.lsb %the input uvdata
gain = uvdata_rx0.lsb %the uvdata that contains the
options = report %to report the mean gains.
out = uvdata_rx0.lsb.rw %the output uvdata in which the
systemp (or variance) has been
mupltiplied by the re-weighting
factors that are calculted based
on the antenna gains.
Note that one must turn on the options=systemp in invert
in the imaging process in order to make this re-weighting effective.
Jun-Hui Zhao (miriad for SMA)