Attached is a plot of the reference cavity transmission and room temperature.  Also plotted are
the quadrant signals from the quadrant photodiode in the ISS box.  The transmission didn't
deteriorate too badly after yesterday's tweak.

The second plot shows the pre-modecleaner temperature and the output of its heater.  Whilst the
heater's job is to keep the pre-modecleaner PZT voltage within its range, it does appear that
the lengthening of the body couples to the pitch (mostly) of the output beam.  THis might be due
to the way the pre-modecleaner body is clamped to its container.