LHO Fellow: Jian Liu

• Observing was 5.2% Monday, 35.3% Tuesday, and 83.1% Wednesday for an average of 41.2%. The main issue on Monday was concern about the fast shutter being stuck open, a danger to the OMC (see alog 37553). The issue on Tuesday was earthquakes. Note that it was realized on Tuesday that only OMC DCPD B rather than both A and B were being used (see alog ( 37585)). Fixing this increased the BNS range from about 45 Mpc to about 57 Mpc.
• Unexplained noise below 90 Hz has persisted since the earthquake on 6 July. Although many investigations have been made (see alog 37599 and comments), the problem remains unsolved.
• The PEM magnetic noise at EY (in X, Y, and Z) increased with a peak at about 30 Hz and a broad band increase below that frequency. The change occurred on 15 July. This channel does not seem to be coherent with h(t). See alog 37657 for more details.
• Some further details are given in the full report about "low frequency" glitches reported by Edmund on 19 July (see alog ( 37609)).

See https://wiki.ligo.org/DetChar/DataQuality/DQShiftLHO20170717 for the complete details.