[mmaimcal]Change to Total Power Detector sampling rate

[Al Wootten]

Mark had another point, which I try to paraphrase thusly: Currently, our
  paradigm is a 5% error in the relative flux scale.  This will not be
  good enough for some mosaicked observations, where such a large
  difference in the interferometer flux scale and the total power flux
  scale will result in imaging errors. How can we improve this?  Mark
  proposes we contemplate a cross calibration of total power and
  interferometric systems by observing a bright quasar with both. At 880
  GHz there should be one 0.5 Jy QSO within 15 degrees or so of the mosaic
  target source.  We can observe that source, but ideally the minute or so
  we'd like to devote to getting good enough S/N on that source will not
  suffice.  We'd need many minutes, perhaps an hour.  But in that period
  of time the sky and the instrument are likely to have changed, so we
  cannot get adequate S/N quickly enough.  However, if we observe with all
  64 antennas, although the TP flux scale on any particular antenna may be
  say 8% off, the mean of all of them would be like 1% off, enabling the
  accurate cross calibration of total power and interferometric
  observations, and allow us to make a high quality mosaicked image.

  I believe that the change should apply to all 64 antennas.

  Comments?  Corrections?

Mark notes that you can also find backing material for this argument in
section 10.2 of https://wikio.nrao.edu/bin/view/ALMA/CalTotalPower