I performed the lockloss investigation of 2024-12-31. Main cause seems to be the oscillation of ~1.69 Hz in ETMX yaw and ASC channels. As I checked the data around the lockloss, there was no ETMY MN oplev glitch. (it was solved?)

Details

• 2024-12-31 11:33:56 UTC
  • The ETMX yaw started oscillating with ~1.69 Hz. The amplitude was growing up with the time. (Fig) (Fig)
  • Similarly, we can see the oscillation with same frequency in ASC signals, such as DHARD_Y, DSOFT_P, DSOFT_Y, CHARD_Y, CSOFT_P, CSOFT_Y. (Fig)
• 2024-12-31 10:29:43 UTC
  • From the 4 min before the lockloss, the ETMX yaw started oscillating with ~1.69 Hz. Coincidently, the amplitude of K1:ASC-INP2_Y_IN1_DQ, ASC channels oscilating with ~1.69 Hz started to increase. (Fig) (Fig) The power of IR started to decrease.
• 2024-12-31 10:10:29 UTC
• 2024-12-31 09:15:50 UTC
  • After reaching the OBSERVATION state, the ETMX yaw started oscillating with ~1.69 Hz. The other phenomena is same as others. (Fig) (Fig)
• 2024-12-31 08:38:19 UT
  • The situation is same as other lock. But, the oscillation stopped during -27min and -21 min before the lockloss, and started the oscillation again. (Fig) (someone was adjusting the control?)
•  2024-12-31 06:58:26 UTC
  • At the -30 s before the lockloss, K1:ASC-DHARD_Y_IN1_DQ started to oscillate with ~0.2Hz. (Fig) At the same time, ETMX_P and ITMX_P started the oscillation. We guess the microseism excited this motion.
• 2024-12-31 04:39:12 UTC
  • At this lockloss, we can't see the oscillation in ETMX yaw.
  • There was the excess in the K1:OMC-TRANS_DC_{A, B}_IN1_DQ at -1m51 of the lockloss and it was decaying with the time. (Fig) At the same time, there was a transient disturbance in ITMY pitch. (Fig)