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Basic Information on mfcal
Task: mfcal
Purpose: Multifrequency antenna and passband calibration.
Categories: calibration
MfCal is a Miriad task which determines calibration corrections
(antenna gains, delay terms and passband responses) from a
multi-frequency observation. The delays and passband are
determined from an average of all the selected data. The gains
are worked out periodically depending upon the user set interval.
Key: vis
Input visibility data file. No default. This can (indeed should)
contain multiple channels and spectral windows. The frequency
set-up can vary with time.
Key: line
Standard line parameter, with standard defaults.
Key: stokes
Stokes parameters to process. The default is to process the parallel
hand polarisations.
Key: edge
The number of channels, at the edges of each spectral window, that
are to be dropped. Either one or two numbers can be given, being the
number of channels at the start and end of each spectral window to be
dropped. If only one number is given, then this number of channels
is dropped from both the start and end of each window. The default
value is 0.
Key: select
Standard uv selection. The default is to select all data.
Key: flux
Three numbers, giving the source flux density, a reference frequency
(in GHz) and the source spectral index. The flux and spectral index
are at the reference frequency. If no values are given, then MFCAL
checks whether the source is one of a set of known sources, and uses the
appropriate flux variation with frequency. Otherwise the default flux
is determined so that the rms gain amplitude is 1, and the default
spectral index is 0. The default reference frequency is the mean of
the frequencies in the input data. Also see the `oldflux' option.
Key: refant
The reference antenna. Default is 3. The reference antenna needs
to be present throughout the observation. Any solution intervals
where the reference antenna is missing are discarded.
Key: minants
The minimum number of antennae that must be present before a
solution is attempted. Default is 2.
Key: interval
This gives one or two numbers, both given in minutes, both being
used to determine the extents of the antenna gain calibration solution
interval. The first gives the maximum length of a solution interval. The
second gives the maximum gap size in a solution interval. A new solution
interval is started when either the max length is exceeded, or a
gap larger than the max gap size is encountered. The default max length is
5 minutes, and the default max gap size is the same as the max length.
Key: options
Extra processing options. Several values can be given, separated by
commas. Minimum match is used. Possible values are:
delay Attempt to solve for the delay parameters. This can
be a large sink of CPU time. This option rarely works and
should be used with caution.
nopassol Do not solve for bandpass shape. In this case if a bandpass
table is present in the visibility data-set, then it will
be applied to the data.
interpolate Interpolate (and extrapolate) via a spline fit (to
the real and imaginary parts) bandpass values for
channels with no solution. This is commonly used because
a set of channels are flagged, possibly because of RFI or
spectral features in the bandpass calibrator. If
less than 50% of the channels are good, the
interpolation (extrapolation) is not done and those
channels will not have a bandpass solution
oldflux This causes MFCAL to use a pre-August 1994 ATCA flux
density scale. See the help on oldflux for more
information.
Key: tol
Solution convergence tolerance. Default is 0.001.