At 23:19, H1 had a lockloss (which was unfortunate because it was starting to ramp up in range!).  There were no seismic event,

BUT....

IMC was not relocking.  No other alarms, so delved into PSL's ISS, and found a couple of issues

1)  ISS Was Saturating

Did not really know to go here other than I rememeber having a Diff for the ISS for last lock.  And sure enough, I saw the ISS not looking healthy.  Eventually called Jason and told him the....

SYMPTOMS:  Diffracted Power racing up to 12% & seconds later it would drop.  It kept on cycling like this. 

Jason told me...

THE FIX: 

• Turn AUTOLOCKER OFF
• Open Manual Mode & turn it OFF (diffracted power will stay at saturated value of 12%)
• Then tweak the REFSIGNAL 5-clicks at a time (I went more negative), until you can get the Diffracted Power between 3.5-4.0%
• Then Turn Manual to ON +INT, wait a few seconds.  Then turn the Autolocker back ON.

2) NOISE EATER OFF
When Cheryl arrived she happened to notice that the NOISE EATER was OFF!  (She also found it went off when the OMC broke lock during the lockloss...so maybe this was the cause of the lockloss?).  I went out and turned it on for Cheryl and she relocked the FSS and is now back to locking.

Note:  I did go to a CORRECTIVE MAINTENANCE Observatory Mode for a few minutes while we were down.