Jason, Rana, John
Credit for this one goes to John Worden. He noticed the sawtooth pattern seen by the ITMy optical lever was very similar to that produced by the instrument air system re-pressurizing itself. Sure enough, we go out and the copper instrument air line is touching the north end of the ITMy transmitter pier, so we moved it. As can be seen on the attached graph, after the move the sawtooth pattern was gone. I'll keep an eye on this over the next couple days to make sure this is actually fixed.
Picture of the fix, taken by Rana. We need to keep an eye on this, and come up with a more permanent fix (right now it would be very easy for someone to mistakenly bump the line right back against the pylon, thereby re-introducing the sawtooth).
In the trend plot above, the calibration of the pit/yaw channels is in units of microradians. Also, during searches for the problem, we have adjusted the laser diode drive current to a higher power. We need to scribe/tape the laser diode knobs to keep the diode current stable.