TravisS, DarkhanT, EvanG, RickS

Late yesterday afternoon, we transitioned to Laser Hazard at Yend (removing Bubba's Lock and Tag on the Pcal power supply after consulting with him).

After orienting the ETM to the pre-vent location on the QPD, we went into the manifold and inspected the Pcal beam positions on the perisocpe relay mirrors.  They looked pretty good on a cursory inspection.  Both beams were also found to be centered on the Receiver module power sensor.  Evan and I centered the beam positions on this sensor before the vent.

Then, using the Working Standard, we measured the beam powers before entering the vacuum enclosure, inside before impinging on the ETM, inside after reflecting from the ETM, and outside at the Receiver Module.  These data, once digested, should allow us to determine where the approx. one percent optical loss between Transmitter and Receiver modules is occurring and thus reduce the Pcal uncertainty slightly.

We then transitioned back to Laser Safe, re-installing Bubba's lock and tag on the Pcal power supply.  Note that the green light supply is not locked out, but the key is removed.

At the next opportunity, we plan to install the Pcal ETM target on the suspension structure and investigate the alignment in more detail.