Description
This function is a specialization of the setsolve method which
should be used when cubic spline G solutions are desired, e.g., when
SNR on calibrators is very low. Currently, this solving mode is available
only for single polarization data.
The visibility data are averaged in frequency (for multi-channel data)
prior to the solution. The spline timescale (time between knots) is
specified in the splinetime paramter, which defaults to
10800 seconds (3 hours).
The solution is performed for phase and/or amplitude according
to the mode parameter. For phase solutions only, use
mode='PHAS'. For amplitude solutions only, use
mode='AMP'. If both are desired,
use mode='PHASAMP', and both will be solved for using the
same spline timescale (this mode also assumes that all calibrators
have the correct relative flux densities).
If solving for phase and amplitude separately (usually in this order),
be sure run setapply to specify application of the first one when
solving for the second one. The combined solution will be stored
in the table specified for the second solve. If it is desired that
the first solution table be preserved, use a new table
name.
Different spline timescales may be used
for phase and amplitude. If multiple fields are present, they will
be used together to obtain a single solution. In mode='AMP',
it is important that the model flux densities of each fields be correct,
so that a single, consistent gain function can be properly determined.
The parameters npointaver and phasewrap tune the
phase-unwrapping algorithm when mode = 'PHAS'. Cycle slips
are detected (and removed before the spline solve) when the median
phase a sequence of length npointaver (in integrations)
differs by more than phasewrap degrees from the previous
sequence.
When solve is run, the solutions are obtained, and postscript
plot of baseline data and solutions is generated and deposited in
your working directory. Its name is the same as table, with
.ps appended.
At this time, it is not yet possible to plot the antenna-based
solutions themselves using plotcal.
After obtained, these solutions should be applied using type='GSPLINE'
in setapply.
Pending improvements:
- Generalize to dual polarization
- Enable plots of antenna-based solutions (currently, only plots of
baseline data and solutions are produced)