Content-type: text/html Manpage of smamfcal


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






SmaMfCal is a Miriad task which determines calibration corrections (antenna gains, delay terms and passband shapes) 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 selected interval. SmaMfcal implements algothrims for weighting, continuum vector normalization, and moving smooth prior to solving for bandpass and gains, which are necessary for handling data at submillimeter wavelength when the S/N is poor and phase dispersion is large. The basic solving algorithms are the same as in Mfcal.  


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.
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. The default value is 0.
Standard uv selection. Default is all data.
Three numbers, giving the source flux, the reference frequency (in GHz) and the source spectral index. The flux and spectral index are at the reference frequency. If not values are given, then SmaMFCAL checks whether the source is one of its 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 or two numbers, both given in minutes, both being used to determine the extents of the gains calibration solution interval. The first gives the max length of a solution interval. The second gives the max gap size in a solution interval. A new solution interval is started when either the max times length is exceeded, or a gap larger than the max gap is encountered. The default max length is 5 minutes, and the max gap size is the same as the max length.
This gives different ways to determine weights (wt) prior to solving for bandpass:
 -1 -> wt = 1; the same weighting method as used in MFCAL.
  1 -> wt ~ amp0**2/var(i); for a normalized channel 
            visibility, the reduced variance is proportional 
            to amp0**2/var(i), where amp0 is the amplitude 
            of the pseudo continuum and var(i) is the variance
            of visibility for the ith channel.
  2 -> wt ~ amp0**4/var(i)**2; 
Default is 2 for SMA and -1 for other telescopes.
     if you have stable phase, use -1;
     if the phase stability is poor, use 1 or 2;
     for a larger planet, 2 is recommended.

For antenna gains' solver:

 -1 -> wt = 1; the same weight method that is used in MFCAL.
 >0 -> wt = 1/var, where var is the visibility variance.
Defualt is 1/var.
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.
  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 (because of flagging).  If
            less than 50% of the channels are unflagged, the
            interpolation (extrapolation) is not done and those
            channels will not have a bandpass solution
  oldflux   This causes SmaMFCAL to use a pre-August 1994 ATCA flux
            density scale. See the help on "oldflux" for more
  msmooth      Do moving average of the uv data (the real and 
               imaginary parts) using the keyword smooth parameters 
               specified prior to solving for bandpass.
  opolyfit     Do least-square fit to the bandpass solutions
               (the real and imaginary parts) with an orthogonal 
               polynomial of degree n which can be given in keyword
  wrap         Don't unwrap phase while do fit or smooth
               the uv data.
  averrll      In the case of solving for bandpass of dual
               polarizations, averrll gives vector average 
               of rr and ll bandpass solutions; the mean value 
               is written into the bandpass table for each of rr 
               and ll.
This gives three parameters of moving smooth calculation of the bandpass/gain curves smooth(1) = K parameter k giving the length 2k+1 of the averaging
               interval; default is 3.
smooth(2) = L order of the averaging polynomial l; default is 1. smooth(3) = P probability P for computing the confidence limits;
               default is 0.9.
polyfit gives a degree of orthogonal polynomial in least-sqaure fit to the bandpass/gain curves. Default is 3. polyfit: 1 (linear), 2 (parabolic), 3 (cubic), ....
Solution convergence tolerance. Default is 0.001.




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