Keita, Kiwamu,

This is a follow up of the previous investigation for the input pointing issue (alog 15028). We are concluding that the IM2 is the one which messed up the input pointing the other day before the temperate issue hit us.

According to a back-of-envelop calculation, this well explains why we had to move IM4 by 88 urad in pitch to get back to good alignment (alog 15063). Also, from the OSEM spectra, there is no obvious indication of the mirror sticking to the cage or something. Therefore we don't think this is an issue.

Here are summary:

• IM2 suddenly moved when HAM2 ISI was restored at around 22:00:00 on Nov 11 (alog 15032)
• The move was mainly in pitch by 60 urad. Yaw moved by only 5 urad and longitudinal was almost nothing.
• After the move, it stayed at the new angle and never came back to where it was.
• So it looks as if the IM2 mirror slipped in pitch.
• The other IMs showed a similar behavior at the same time, but they are smaller than IM2 did.
• We checked the ASC and some other dignal paths, but there had been no signals other than the alignment biases. So we think it happened mechanically.

The attached is trend of various relevant signals:

Here is the spectra of the OSEMS before and after the slip. The bold curves are the ones taken on Nov 10 and the thin curves are the ones from today. All the spectra from today are consistenly lower at low frequencies supposedly due to different seismic level. Also we are having a small bump at around 2 Hz today for some unknown reason. In any case, we don't see an obivous indication of the mirror touching the cage or OSEMs. Therefore we are concluding that IM2 is still healthy.