Sheila, Tony, Camilla
Sheila and Tony noticed that we had a ~30 minute 10MPc range drop last night with related extra low-freq glitches, from the range BLRMs this is most clear in th 20-34Hz band. This noise is broadband 15-100Hz looking at DARM, plot. And trending the common range drop channels form last year, plot, we see a slight increase in FC2_M3_NOISEMON, plot, confirmed as the cause by the dtt spectrum. Sheila is proposes the cause could be FC backscatter into the IFO. There is no increase in FC1 noise apart from small regions at 80Hz, 160Hz, 190Hz, plot.
There is slighly more noise 8-20Hz in HAM8 in the low range time and 3 peaks at 7-9Hz are gone, plot.
We see the same increased noise in H1:SUS-FC2_M3_NOISEMON_LL_OUT16 in the early morning range drop, see attached.
Running the same template as yesterday, attached yellow traces, there is increased noise in the FC2 and FC LSC control channels, more noise in HAM8 ISI, and a ISI peak at 3.3Hz (there was an earthquake 45mins before but the FC noise started before the EQ), however, the noise in DARM is actually less than yesterday so the coupling isn't constant.
Jim and I had a look at the HAM8 motion and although it increases at times when the ground motion increases, these times do not seem correlated with the FC excess movement and range drops, attached. Maybe the 3.3Hz ISI peak is related to the noisier ground motion times.
