Content-type: text/html Manpage of mfcal


Section: User Commands (1)
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mfcal - Multifrequency antenna and passband 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.  


Input visibility data file. No default. This can (indeed should) contain multiple channels and spectral windows. The frequency set-up can vary with time.
Standard line parameter, with standard defaults.
Stokes parameters to process. The default is to process the parallel hand polarisations.
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.
Standard uv selection. The default is to select all data.
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.
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.
The minimum number of antennae that must be present before a solution is attempted. Default is 2.
This gives one, two or three numbers, all given in minutes, being used to determine the extents of the antenna gain and passband 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. The third number specifies the passband solution interval. The default is to use a single passband solution for the entire observation. Each passband solution interval will consist of one or more full gain solution intervals.
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
  noxyalign By default, when computing bandpasses for dual-feed antennas,
            MFCAL will write a solution in which the antenna gain phases
            for both feeds are the same and the bandpass phases
            for the Y feeds are not centered on zero. This allows for
            higher-sensitivity phase solutions during later calibration
            since one can solve for a single phase for each antenna using
            both X and Y data, if the bandpass solution has been applied.
            If this option is supplied, all of the bandpass phases will
            be centered on zero and the antenna gain phases for the two
            feeds on each antenna will differ.
Solution convergence tolerance. Default is 0.001.




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Time: 18:35:38 GMT, July 05, 2011