Suspension related topics during the alignment work:

1. XARM was aligned with the current usual procedure (klog29346).
2. SR3 was aligned so that GRY beam hit on the ETMY center by using Tcam.
3. Place PD at EYA chamber so that GRY beam hit on the center of PD.
4. Align BS to hit the IR beam on the center of the PD.

Since GV between IYA and Y arm was opened, alignment of SR3 and BS were changed several tens of urad in the same direction but as reported in the original log, no significant change can be observed on SR3 and SR2 beam spot.

To center the beam spot on SRM target, SR2 was moved along minus pitch direction by about -1500 cnts at IM OPTICALIGN OFFSET with OLDAMP_OFF state (since OpLev became out of range during the work, we could not use OpLev setpoint for the alignment).
After that, Dan and Hirata-san performed centering of SR2 OpLev, so now SR2 good alignment can be reproduced at ALIGNED state.
During the SRM reflection beam investigation, I requested PAYFLOAT state for SRM and excite 0.84Hz pitch resonance from TM_TEST_P_EXC with several hundred cunts, which causes +/-200 urad oscillation of SRM.
Since the distance between SRM and SR2 is 15m, +/-200 urad shakes the beam by several mm at SR2, which should be visible if we found the SRM reflection at SR2 with sensor cards (unforetunately, we could not find the beam, though).

Note:

BS actuators are weak and sometimes BS control was saturate when SR3 side flange was opened (somehow SR2 and SRM side flanges didn't make BS saturated. Maybe air flow is different? SR3 COACH was placed in front of the opened flange while the others are slightly off from the flanges).
So, when SR3 side flange is opened, BS needs to be manually aligned at DAMPED state with IM_OPTICALIGN.