travis.sadecki@LIGO.ORG - posted 15:10, Friday 04 August 2017 - last comment - 18:07, Friday 04 August 2017(38000)
GRB alert during Commissioning
We received a GRB alert at 21:53 UTC. However, Sheila was doing some noise hunting at EX at the time. I let her know about the GRB and she stopped what she was doing. I went to Observing at 22:03 UTC, only to find out when Sheila returned that the EX ESD (whose SDF diffs we had to accept to return to Observing) was in a half-connected state. We dropped back out of Observing, reverted the settings, and returned to Observing at 22:09 UTC.
Note for next Operator/lockloss: The ETMx ESD bias will have an SDF diff. This should be ACCEPTED.
For this test, I ramped down the bias, drove the end station, turned off the ESD driver, and started disconnecting ESD cables. Travis took references, which are attached. It is interesting that we got a large noise peak around 60Hz when we had LL and UL disconnected, which went away when I disconnected LR.
After I disconnected LR, we got the GRB alert, I decided to leave the bias off (since it doesn't matter to the noise) and leave the ESD cables as is since I didn't want to risk unlocking the IFO by reconnecting them. I had thought that what I had been doing was probably not impacting the data quality in the half hour before the GRB alert, so that it would still be worth having people analyze the data. Now I see that I was causing large glitches during that time, so this probably isn't useful data.
I had intended not to turn back on the ESD driver in this state, but people in the control room weren't aware and turned it back on. This means that the bias was on although there was no signal sent to the quadrants. (Only the bias and UR cables were connected.) We decided not to leave it like this, so went out of observing to turn off the ESD driver again.
I went out again and disconnected UR (noise on the reference) but disconnecting the bias unlocked the interferometer. the cables I brought out weren't the right gender, so I wasn't able to terminate them.