Patrick T, Dave B, Jonathan H, Sheila D, TJ S

Summary: Today during maintenance more of the cameras were swapped over to the new camera code on a new server. This caused a lock loss since there was an offset with the new camera code, so the code and servers were swapped back for most cameras.

Some of these swapped cameras are ones we use in locking. At the end of maintenance, I skipped over initial alignment and started to lock the IFO. When we got to the ISC_LOCK state ADS_TO_CAMERAS, we could see the PRG get pulled away over a minute, as well as other signals on the FOMS, before we lost lock. Looking into it, the calulated P & Y, or X & Y depending on which channel you're looking at, channels were different from before the camera swap. The offset that this created moved us away from our alignment setpoints to cause the lock loss. Had I ran an initial alignment we might have run into this soon as we use the green ITM cameras, but we might have lost our alignment references there as well.

While it is possible to find and try to adjust for all of the offsets that the new code introduced, it would be much safer to do this after the IFO achieved full lock and we could transition the IFO off of the cameras, switch to the new code/servers, and then see what the offset is and adjust accordingly. Doing it while not locked risks losing our saved offsets, so we decided to revert the code and server changes for today and plan for another day to implement this.