[Craig, Georgia, Sheila, Gabriele, Peter, Elenna, Jenne]
The IFO is moving much more than normal at ~1 Hz in yaw. It's most clear when looking at the beam positions on the AS_A and AS_B WFS, but we're still not sure where the problem is. The buildups start to get wobby when we do Engage_ASC_for_full_IFO. SRM yaw sees the motion very clearly, but that seems to be a loop effect. When we turn off both SRC1 and SRC2, we see that the SRM motion decreases to a more normal level, but the AS WFS spots still move a lot (~10x more than normal), the AS AIR camera looks wobbly, and our buildups are wobbly. There is some motion on AS_C, but it's much more clear in AS_A and AS_B, which makes me think it's cause is something after the beam arrives in HAM6.
Sheila noted that in the past we've been able to change instabilities in our AS DC centering loops by changing the DARM offset. I did that today (lowered from ~42pm to 35pm, or 20mA to ~13mA), but didn't see a change in the behavior.
I increased the gains of all 3 AS DC centering loops by 10dB (turned off -10dB filters), but that made things more unstable. Maybe that's a clue?
I have not looked closely yet at the OMC ASC, so perhaps there's something to look at there?
There was an ASC model boot today around lunchtime, but I thought that I had cleared the SDFs before then. I've also gone back to a previous safe.snap file from May 25th, and I don't see any diffs that seem strange or unusual. So, it's highly suspicious that I did an ASC model boot today (only change was to create 4 sender IPCs), but I just am not yet seeing anything that is due to that boot. The one big thing could be dark offsets - Georgia is running the dark offset script now that we've lost lock and Craig took the IMC to OFFLINE.
I think another thing to do is to go to PREP_ASC_FOR_FULL_IFO, and see what the ASC error signals (including the DC centerings) look like. Maybe that should even be done before DRMI ASC is engaged?
Tony and I compared the suspensions from the weekend (gps 1337926070) when the IFO was unlocked in ISC_LOCK state READY to this morning unlocked in READY (gps: 1338127913). The issue is at ~0.7Hz. ITMY now seems noisier at this frequency in yaw now. ETMY looks the same.
ETMX and ITMX OPLEV Pitch and Yaw over the weekend in ISC_LOCK state Ready, compaired to this morning's ISC_LOCK state Ready.
ETMX OPLEV seems oddly noisy, and strangely shaped.