[daip] Info on PCAL, LPCAL, and SPCAL

[Craig Walker]

I'm now doing my first VLBA polarization calibration (!) so I am likely
to have some comments, especially about the documentation.  Here is
the first, rather simple one.

As I look at the cookbook chapters on VLBI (not much in the VLBA recipe
chapter about polarization), I see PCAL, LPCAL, and SPCAL mentioned.  So an early
decision to make is which one to use.  But I find that you have to dig
fairly far into the help files to find out which is appropriate.  It would
be useful for the cookbook and for at least the odd case programs (like LPCAL)
to have a sentence right up front about what they are for.  Most
users could skip on at that point.

Note that just saying the SPCAL is for spectral line doesn't help much because
all VLBI data is spectral line at this stage of the process.  I am still fuzzy
on what is different about SPCAL.

Craig

PS - I wrote this in the morning today, before I talked to Eric.  Then I
forgot to send it.

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    R. Craig Walker            Array Operations Center
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