K. Tanaka, Akutsu

Installed the Cat.B viewport window (prepaired yesterday) for the transmitting IR and green light at EXT (Fig 1). Then tweaked some mirrors on the optical table in air to compensate the shifts and the tilt of the green/IR beam paths due to the thickness and the wedge angle of the viewport window. During the work, we did not touch periscope towers including the mirrors there for both of the green and IR.
On some mirrors the light spots are not centered, but we would like to quickly recover the reference-loss situation today, so we left them as were. Then tweaked the steering mirrors in front of the CCDs and DC-PDs for the green/IR respectively so that thier images were put at the center of the CCD views, and the outputs of the DCPDs were maximized as much as possible.

By the way, it is interesting that we can clearly see a "green beam ray" at the left-hand side in the window. This should be the main axis of the transmitting green beam (Fig 2).

For the beam centering on the periscopes; for IR, they are shifted (Fig 3) so we would need to re-centered by moving the periscope? later; For green they are almost centered (Fig 4), as they were shifted before installing the viewport window .