H1 called for assistance at 08:45 UTC because it was able to lock up to NLN, but could not inject squeezing due to an error with the SQZ TTFSS. The specific error it reported was "Fiber trans PD error," then on the fiber trans screen it showed a "Power limit exceeded" message. The input power to the TTFSS (SQZ-FIBR_TRANS_DC_POWER) was indeed too high at 0.42mW where the high power limit was set at 0.40mW. Trending this back a few days, it seems that the power jumped up in the morning on July 3rd (I suspect when the fiber pickoff in the PSL was aligned) and it has been floating around that high power limit ever since. I'm not exactly sure why this time it was an issue, as we've had several hours of observing time since then.

I raised the high power limit from 0.40mW to 0.45mW, the TTFSS was able to lock without issue, SQZ_MANAGER brought all nodes up, and squeezing was injected as usual. I then accepted the new high power limit in SDF (attached) for H1 to start observing at 09:20 UTC.

Since this feels like a Band-Aid solution just to get H1 observing tonight, I encourage someone with more knowledge of the SQZ TTFSS to look into it as time allows.