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Handling for Baseline-based Bandpass Errors with Weaker/Resolved Calibrators

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