We moved the IMC offsets, injecting lines in PIT and YAW on the IMC PZT around 400 Hz, and saw the improvement in the red trace on the second attachment. 

• We watched the lines in DARM and tried to move the IMC offsets to miminize the peaks (similar to what Robert and Kiwamu did in alog 29523). 
• We had tried to minize the jitter to intensity coupling in the IMC yesterday by watching the ISS second loop diodes, but were unable to do better than with no offsets in.  Watching DARM things were much more repeatable and stationary, which makes me think that whatever we are minimizing this way, it is not jitter to intensity coupling in the IMC.  We were suprised that moving the IMC alingment had a repeatable impact on the high frequency noise which is coherent with REFL.  We found that for IMC DOF1 P (which actuates on MC2 using a combination of the WFS signals) a good offset was 170 cnts.  We only tried DOF1 P and Y, so a more precise tunning could be done.  

Tonight we did a few more measurements to try to understand the jitter coupling:

• After powering up, I did some yaw injections on the IMC PZT while Jenne changed modulation depths, which had no impact on the measured coupling, suggesting that the jitter couples to DARM through the carrier field.  We made a reference injection at 01:13:26 Sept 22 2016 UTC, Jenne reduced the 9MHz modulation depth by 6dB (injection at 01:17:35), and then increased the 45 MHz modulation depth by 3dB (injection at 1:24:02).
• We later tried a test of changing the DARM offset, to see what impact it has on our noise, and while doing this did a few more excitations.  Changing the DARM offset had no impact on the measured coupling either, suggesting that jitter (edit: should not be) be coupling to the DC PDs on contrast defect light.
• The coupling for yaw did drop by almost 6dB, (without much change in shape) after the interferometer had been locked for several hours.  This could be consistent with the contrast defect or alingment changing as the interferometer thermalizes. We did not do a before/after thermalizing measurement for pit, but it might be interesting to try this tomorow. While the noise from 200Hz-1 kHz didn't improve dramatically with the thermal change, there are a few peaks that were smaller after the change, (compare blue to purple in the second attached screenshot)
• After moving the IMC P, the shape of the transfer frunction from IMC PZT yaw to DARM changed with the sharp features gone.