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The lack of strong point source for bandpass calibration
is the well known problem. Often we run out of the signal budget
in baseline-based bandpass calibration. The problem gets worse
at the short sub-millimeter wavelengths. Although the
planets and the Moon have strong dust emission, the structure of the disk
might ruin the closure relation. Miriad smablsrc
can turn a planet or the rim of the Moon
to a pseudo-point source for the purpose of
baseline-based bandpass calibration.
Here is a usage:
smablsrc vis=uvdata \
select='source(mars)' \
out=marsSblsrc
The output file marsSblsrc contains the uv data of the pseudo-point source,
which can be used for baseline-based bandpass calibration using
blcal.
In addition, the phase fluctuation are naturally canceled out in
the normalization process. One can process the data of weaker point sources
using smablsrc
prior to integrating the visibility
data together to
improve S/N for the purpose of baseline-based bandpass calibration:
smablsrc vis=uvdata \
select='source(3c111,1924-292)' \
out=weakSblsrc
Jun-Hui Zhao (miriad for SMA)
2012-07-09