TJ, Sheila, Betsy, Jim 

Since we have had increasing drift in the PR3 yaw alignment needed to get ALS beatnotes good enough to lock, we realigned the beat notes on ISCT1 this afternoon.  First we set the green x arm references as we found them yesterday while locked with 2W and the spots centered on the optics (69857).  Screenshot attached of accepting these new references in SDF.  

TJ then ran an intial alignment through the MICH alignment step, we saw that COMM beatnote was -18dBm, TJ adjusted PR3 yaw to 147.2urad to increase the COMM beatnote to -10dBm; 2 weeks ago PR3 yaw was at 151.6 urad so this is an pparnt drift of 4.4 urad.  The osems and optical lever do not indicate that PR3 has had any drift like this.  

TJ and I went to ISCT1, looked at the beampaths which were mostly reasonably centered with PR3 at 147.2urad, then asked Jim to move it to 151.6 to restore PR3 to it's alignment of 2 weeks ago.  Then the Y arm beam was hitting the X arm side of the prism and being directed into the X arm path.  We adjusted mostly yaw and a little pitch on the bottom periscope mirror, (layout here), as well as the yaw of the 1 inch BS that splits the X beam between the trans PD path and the beatnote paths, to get both X and Y beams roughly aligned through the paths to the comm and diff beamsplitters. 

From there we manually aligned the COMM beatnote, with an IR card then the scope, and got a beatnote strength of 7-8 dBm, for DIFF we have -8.2dBm.  The arm transmission diodes were lower than previously, so Betsy and I went back to the table and checked that the beams were centered on the trans PDs, which didn't increase the power.  Corey and I then re-normalized the trans diodes, by adding a gain of 1.16 to the Y channel and 1.35 to the X channel.  The changes in screenshots on this alog will need to be accepted in OBSERVE.