J. Kissel

I've noticed the amplitude spectral density of PCALY RX PD looks to be showing the same sort of clipping behavior that was present early last October (Identified in LHO aLOG 30827; Solved in LHO aLOG 30877). I'll send a note to team PCAL and suggest they take a look tomorrow during maintenance.

The attached plot shows the ASD of PCALY RX PD (in PURPLE) and CAL-DELTAL_EXTERNAL (in RED) during the most recent lock stretch (2017-01-09 19:30:49 UTC) compared against PCALY RX PD right after they'd fixed the clipping issue last time (2016-10-26 17:26:40 UTC).

Unclear why the clipping has returned, other than to say that what is a "good" alignment of ETMY that the exit PCAL beams were aligned to may have changed / drifted over time. A 20 day trend shows that clipping only started after the IFO returned to operation on Jan 4th.