After Keita aligned ITMX (see 9071), I aligned the corner PRMI using ITMX as a reference. It is flashing now.

Sadly, I still don't see the POP beam either on HAM1 or ISCT1. Also, I looked at the POP penetration hole (swiss cheese baffle) with the camera at HAM3 spool, but no sign of a clipping or scattering was found.

The screenshot below is the current best alignment:

The alignment of the day:

• I restored the IM alignments back to that of the last week (alog 9016) because I needed the REFL beam for aligning PRM.
• I  centered the beam on PR2. I used a HAM2 spool camera to look at PR2.
  • Because IM4 was not able to bring the beam from an edge to another edge of the aperture on the scraper baffle, I offloaded the DC bias to IM3 both in pitch and yaw.
  • The centering was done by taking the middle point between points where I saw a bright scattering from the aperture of the scraper baffle.
• PRM was aligned such that the REFLAIR_A_LF was maxmiazed.
• I centered the beam on PR3 by steering PR2. I used a HAM3 spool camera to look at PR3.
  • By introducing a big misalignment in pitch, I could let the beam hit the lower earthquake stops. The horizontal alignment was adjusted to be the mid-point of the two earthquake stops.
  • The vertical alignment was done by taking the middle point of points where the beam illuminated either lower or upper side of the mirror edge (perhaps the cage).
• I steered PR3 until PRX flashed with ITMX untouched.
• I steered ITMY until PRY flashed.