10 days ago, Gabriele and Evan reported that there seemed to be a large offset in the IMC locking loop (alog 17131). In order to investigate this issue, I started from checking the health of the IOT2L optical table -- specifically we wanted to confirm that there is no stupid clipping or something crazy.

I did not find a clipping or anything crazy on the table.

(Health check of IOT2L)

I went to the IOT2L and checked the REFL path using a IR viewer and card, but I did not find an obvious clipping or any suspicious things. I found an iris which was letting the main beam go through but also scattering ghosts beams. The iris was in front of the BS which steers the beam to the REFL RFPD. I took out the iris and re-adjusted the razer blade beam dumps which have been meant to damp those ghosts. Also, I checked the centering of the beam on the REFL RFPD by steering the BS, but it was already centered.

(What happened to MC trans digital camera ?)

BTW, the IMC trans camera had been displaying nothing these days according to the hourly archives probably since some time in February. I realigned the camera as it seemed to be misaligned in YAW.  After adjusting the exposure, I realized that the beam shape completely changed from the image that I remembered -- see the attached pictures. The first attachment is the one from Feb-04-2015 and the second from today after my realignment. During the realignment process, I moved the camera position to see if this image is something bogus or real. I am concluding that this image is real. Something must have happened in the IMC trans path between early February and now. Sad.