Oli, Louis, Caroline, Sheila, Elenna, Gabriele

At the start of the day I did a check by measuring the ETMX M0 L2L transfer function and saw that with the alignment offsets ON and the R0 yaw offset of -25000 ct, we still see no evidence of rubbing in the transfer function.

Then, I locked ALS on both arms, and was able to drive tidal feedback and WFS feedback to ETMX.

Louis and I proceeded to lock ALS diff on ETMX and started troubleshooting the issues with ALS diff on ETMY.

In short, we still have no idea what the issue is. I measured a transfer function of ETMX L1 to DARM err and compared it to the same transfer function from ETMY L1. They are the same except for an overall minus sign, which is expected.

We then tried to do the sam measurement of the ETMY L3 feedback, but held in down due to an earthquake. After the earthquake, I found we could not lock ALSX and send tidal feedback to ETMX L1. This indicated rubbing again, but the transfer function showed no rubbing.

I was able to turn on the WFS control to ETMX, which drives L2 and M0, and this works fine. The problem seems to be confined to ETMX L1.

I have attached some screenshots and also SDFs that came up during the day- I had to SDF the ETMY L2 length feedback switch OFF and I SDFed the ETMX R0 yaw offset.