[daip] adding de-corr'n to TVFLG/UVFLG/EDITR/VPLOT/UVPLT

[Michael Rupen]

Dear DAIP,
  this is a suggestion/request rather than a bug report (!).  I've been
chatting with Claire Chandler about high-frequency VLA reductions, and she's
convinced me that the de-correlation is a useful way of looking at the data
quality (and flagging bad baselines, at least initially).  [I had previously
argued that PHASE DIFF and the like were equally good, but it's true that
what you're really interested in is the de-correlation, so it would be nice
to have access to that directly.]  Currently the de-correlation is available
only through IBLED, which is painful enough for VLBI data sets, and frankly
appalling for the VLA.  Claire tells me she's gone through IBLED for every
VLA baseline, three times, for one (many hour-long!) VLA run.  She still
seems sane, which astonishes me, but I hate to think of anyone doing this
ever again!  So:
  
  Would you consider adding the option to plot the (and/or flag by)
de-correlation in
       TVFLG
       UVFLG
       EDITR
       VPLOT
       UVPLT
This would be an enormous gain both for VLA users (esp. at high freq.), and
for all VLBIers (e.g. we flagged all the SN93J data on decorrelation,
baseline by baseline, using IBLED -- ugh!!!).  Note also that folks from the
mm interferometers (OVRO, BIMA) are taught to use the de-correlation  as a
primary flagging tool (which I suspect is how Claire got going on this), as are
old-style VLBIers.

  Thanks,

           Michael