Sheila, Lisa, Keita, Daniel, ...

Here are a few plots ilustrating our intensity noise situation.

• The first attachment is the spectrum taken after 1 hour at 50 Watts, with ASC in the high bandwidth state, so the ASC noise dominates up to 300 Hz.  You can see that there is a high coherence with intensity noise (yellow) above a few hundred Hz, and frequency noise coherence is large above a few kHz. At the peaks of intensity noise there is coherence with all the PSL accelerometers, microphones, ect.
• The coupling of intensity noise (measured passively) is shown in the second attachment. This is about a factor of 3 worse the the coupling measured by Evan durring O1 (25476)
• The alingment of the PMC was better in July than it is now. (last attachment).  This may explain some jitter to intensity noise coupling on the PSL table which shows up as more noise in the ISS loop.
• The intensity noise from the first loop is worse than when Evan and Keita measured it in February 26773.  (last attachment, PDB is now the out of loop sensor, this was measured with the second loop off so it should be comparable to the attachment from February).  There are several broad accoustic peaks in the new spectrum that aren't in the February spectrum, and have coherence with PSL table accelerometers between 100Hz and 1 kHz.  The out of loop sensor is a factor of 5 more noisy at 100 Hz, and there are frequencies where it is a factor of 10 worse, after the IMC things are a factor of 3-5 worse. 

It seems possible that a worse alingment on the PSL table since July (ER9) is contributing to our worse intensity noise.  It might be worth considering a PSL incursion to align through the PMC better to take care of some of these peaks, as seen by the first loop PDs at least.