Alexa, Thomas, Evan

Conclusion: it appears that we are at a good low loss point for the IR without having to adjust the green QPD offsets.

I locked both the IR and green to the Yarm. The alignment steps I took were the following:

1. I ran the ditherAlign.py script to center the TMSY pointing using the ITM baffle PDs.

2. I had to walk ITMY, ETMY to get high enough flashes in the arm cavity, and then was able to lock the arm on green and engage the green wfs (all 6 DOFs). This brought the green TR buildup to 1.024 cnts.

3. I then locked the IR to the Y arm and engaged the input pointing wfs to PR2, and IM4. This brought the IR TR buildup to 11 cnts.

At this spot, I measured the LSC-ASAIR_A_LF _OUT counts and found Poff = 1304(5) and Pon = 1262(4), this gives an equivalent ETM loss of L = 125(19) ppm. This was calculated following the equations in alog 15874 and 15470. This is a low enough loss spot, and both the IR and green TR buildups are high. I did not have to adjust the QPD offsets (i.e. adjust the green input pointing).

Evan and I were trying to figure out why these results are better than the previous ones in alog 15874. For one the green wfs were not enabled, although the green TR buildup was similar.  We are going to repeat this measurement over a few mornings and see how consistent of a loss we get with this alignment procedure.