Basic Information on uvdecor

Task: uvdecor
Purpose: Apply decorrelation correction to visibility file
Categories: uv analysis

UVDECOR acts similarly to UVCAT but applies a correction factor 
(>1) to the visibility amplitudes to account for the amplitude loss
due to decorrelation.  The integration time is divided by the
square of the correction factor to reflect the increased noise.
The correction factor is normally derived from the CARMAphase monitor 
data, which is scaled to the appropriate frequency, baseline, and elevation
using a simple prescription for 3D Kolmogorov turbulence.  This task
should be used with caution, as the correction is only valid over
long (>10 min) averaging intervals, and the assumption of 3D
turbulence is unlikely to apply on long (>100m) baselines.

Another optional correction factor should be derived, again with caution,
for CARMA data preceding 26-aug-2007 where decorrelation was present
down to about 8000 ns in the delaylength difference between two
antennas.

Key: vis
The names of the input uv data sets. Multiple names can be given,
separated by commas. At least one name must be given.

Key: select
The normal uv selection commands. One unusual aspect of this is that
the window subcommand can be used to select which windows are
copied to the output file (normally the window only has an
effect for velocity line type). The default is to copy everything.

Key: rmpmax
1 or 2 parameters.  First, maximum acceptable value for rmspath  
in microns.  Default=2000.  Second, type of replacement for bad
values: "zero" to set rmspath=0 (no correction), "extrap" to use 
previous value.  Default="zero".

Key: cormax
Maximum allowed correction factor for the visibility amplitude.
If correction is not prevented by rmpmax, it can still be prevented 
at this stage.  Default=100.

Key: stokes
If a value is given, uvdecor converts the input into the required
polarizations before writing to the output. Default is to copy
across the polarizations present in the input files.

Key: delaymax
If used, this will be the delay difference length (in nanosecs) at 
which the decorrellation would have been 0. 
If 0 is set, this option is not used.
A good value for CARMA data prior to 26-nov-2007 is about 8500 (TBA).

Key: options
This gives extra processing options. Several options can be given,
each separated by commas. They may be abbreivated to the minimum
needed to avoid ambiguity. Possible options are:
   'nocal'       Do not apply the gains file. By default, UVDECOR
                 applies the gains file in copying the data.
   'nopass'      Do not apply bandpass corrections. By default, UVDECOR
                 applies bandpass corrections if possible.
   'nopol'       Do not apply polarization correction. By
                 default UVDECOR corrects polarizations, if possible.
   'nowide'      Do not copy across wide-band channels.
   'nochannel'   Do not copy across spectral channels.
   'unflagged'   Copy only those records where there are some
                 unflagged visibilites.

Key: out
The name of the output uv data set. No default.

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