Reported here by Jim.  This trip was caused by the 35W FE power watchdog tripping, there by shutting down the PSL.  It appears to have been caused by the NPRO shutting off.  Attachment 1 shows the output powers of the 35W FE and the HPO, as well as the power watchdogs for each laser.  It is clear that the FE watchdog trips several seconds before the HPO watchdog trips.  The second attachment shows the output power of the NPRO and the 35W FE power watchdog; it is clear the watchdog trip coincides with the NPRO shutting off.  At this time the cause of the NPRO shut-down is unclear.

The PSL itself was restarted without issue, but as Jim mentioned in his above-linked alog there was an issue relocking the ISS; this was resolved by locking the PMC (since the in-loop PD for the ISS is beyond the PMC, so if the PMC is unlocked, the ISS will not lock).  I had an issue with my remote login not being able to bring up a sitemap (command not found?), so I drove out to the site to investigate.  When I showed up onsite, the lock request for the PMC was OFF (this is obviously not the nominal configuration for a locked PMC).  When the laser was restarted I asked Jim if the PMC was locked and he indicated it was, but when I arrived onsite it was not.  Not sure what happened here.  I know there is a script responsible for turning the PMC and FSS off in the event of laser power loss, but I believe this script also turns them back on once power is restored; I will follow up with TJ, the script's author, about this functionality.  In the previous 2017 laser trips this issue has not been encountered (i.e. open the HPO external shutter and the PMC and FSS have locked right up, no further action required).  Maybe this script didn't quite work right this time?  At any rate, everything is functioning normally now and the IFO is currently relocking (engaging ASC as I type this).  I will investigate more in the morning, for now I'm going to try to get some sleep.