For the past few days the ISS actuator has been swinging around more than it should.  This was remedied by adjusting the
REFSIGNAL slider.  This setpoint indirectly sets the power incident on the PMC.  in some sense there should be no reason
to change the setting unless the power out of the laser has increased or decreased.

The REFSIGNAL slider was adjusted from -2.03 to -1.98.  Which implies a 2.5% decrease in power ((2.03 - 1.98) / 2.03 x 100).
Prior to that the output power of the laser only decreased by less than 1%.  The power transmitted by the PMC varied by ~2.8%.
The reference cavity transmission decreased by ~14%.  We already know there is a drift in the optical path to the reference
cavity.  The ISS railings are due to fluctuations in the PMC transmission.

We should examine the performance of the PMC more closely to see if we can decrease the power fluctuations out of the PMC.
Alternatively we can diffract more light to compensate for the drifts in PMC transmission.