Attached below are power spectra of ETMX main chain OSEM and optical lever signals from Monday January 13, 2014 through Thursday January 16, 2014. The magnitude of all signals has decreased by about a factor of 100 since Monday.

On the PUM stage of the ETMX, the upper left OSEM is noisier than its counterparts as can be seen from the ambient noise figures. It's possible that this OSEM signal is not being correctly filtered, or there may be a problem with the OSEM itself (cabling, led, or photodiode, etc). This isn't a huge problem that we have to fix but is worth noting while we are undergoing ER5. Also attached is a coherence plot between L2 stage OSEMs and optical lever pitch and yaw. The sensors are highly coherent near the suspension resonance peaks, but are pretty incoherent after about 2.5 Hz. The problematic upper left OSEM is less coherent with optical lever pitch and yaw, which again suggests that this sensor has some electronic issue.