The ITMY OPLEV SUM has been oscillating with 10min-ish period for a while. Apparently YAW picks this up with 3urad pp amplitude, making it unusable as an angle monitor (first plot).
It's getting worse slowly. On Tuesday the oscillation was there but it was about 1urad pp (2nd plot).
Something happened on Wednesday afternoon and the SUM dropped by a factor of 2 (third plot), but it's not like the noise didn't jump jumped up right after that event.
Though this is not blocking the locking activity, II asked Doug if he can swap the laser during maintenance. If not, he might try early morning on Wed. or Thu.
While I can't comment on the apparent noise increase, the sawtooth with the 10 minute period looks like the problem we had last September. Check to see if the copper lines that carry the instrument air are not touching the transmitter pylon; the instrument air line is what causes the 10 minute period sawtooth. See alog 13932 for when this happened last September, with pictures.