Brina, Marissa
We noticed that there seems to be a daily drop in the BNS range by a few megaparsecs for about 10 minutes at around 17:00 UTC. I have found it most clearly since June 22, but there are a couple of times before that.
I scrolled through the daily Lasso pages and found that two of the days (June 24 and 25) picked up the channel H1:SUS-ITMY_L3_OPLEV_BLRMS_P_3_10 as correlated with this dip (see this figure). On June 30 lasso picked up the channels H0:VAC-LY_TERM_M17_CHAN2_IN_{MA, COUNTS} and H0:VAC-LY_CP1_PT101_DISCHARGE_PRESS_{MA/PSIG}.mean (figure).
I plotted H1:SUS-ITMY_L3_OPLEV_BLRMS_P_3_10 and H0:VAC-LY_TERM_M17_CHAN2_IN_MA for June 22 - 25, 28, 30, July 6-8, and saw that both channels spike each day at the same time as the drop in range.
I’ve attached examples from June 23 and July 7 showing the lineup of these channels at 17 UTC. I have not yet checked to see if these channels spike at other times causing dips in the range, but I haven’t noticed any other regular times with dips like these.
Just from looking at the summary pages, we weren't able to see anything noticeable in the strain spectrogram at these times. We made spectra comparing a few minutes before the range drop (16:55) and during the range drop (17:02) - see attached spectrum. We did this for a couple of times and don't see a huge obvious difference, but during the dip the spectrum does show slightly higher noise from around 20-200Hz.
This is likely correlated to the daily fill of CP1 based on the timing. Interesting about the noticeable range drop during observing, though.
Tagging VE
Note that the CP1 autofills were moved from 20:00 UTC to 17:00 UTC on May 4 (aLog 69315).
On all the six occasional of the CP1 fill last week, we see this drop in the range (plot attached).
