Varun, Sheila, Georgia, Craig, Cao, Robert

Alignment:

• We ran initial alignment using the green references and AS_C references we did yesterday, which did bring us into lock with a recycling gain of around 42.
• SRY: We have been consistently having trouble with SRY, when things aren't well aligned it won't lock.  We took a couple of minutes today to measure the OLG of the SRY loop and saw that the gain is verry low compared to the reference I had saved.  It looks like we could use 20dB more gain in this loop.  I added a factor of three more gain for SRY locking, and this did help it lock for an alignment which it wasn't locking at earlier (second attachment red is measurement with SRY gain set to 30000, already increased by a factor of 3.  Blue is an old reference from July 2018).
• We with the new centering on AS_C, we were able to engage SRC asc in both DRMI and full lock without problems, so both of those are now back in the gaurdian.
• We were able to engage ADS without problems once the SRC ASC was working, when the ADS came on and brought the spots to the center of the optics our PRG monitor read 47.
• We have split the ENGAGE_SOFT_LOOPS guardian state, which had 8 steps, into two states.  ENGAGE_SOFT_LOOPS is now engaging the soft loops and ADS to bring the spots to the center of the optic, while MOVE_SPOTS moves the spots to the positions we use for power up, adjusts ASC gains, and engage's Hang's ISI to M0 feedforward.
• Using the newly split ADS states, we reset the green references with the spots centered on the optics (1st attached screenshot). 
• Because of a new peak in DARM that Robert found had some coherence with HAM2, we looked at alignment references for HAM2, and saw that IM3 yaw was moved almost a thousand sliders counts on Monday afternoon.  There's nothing about this in the alog, but it could have been related to SRMI work that afternoon maybe.  There was a large shift in the beam position on IM4 trans and the ISS 2nd loop QPD at that time compared to the positions in O3a (third attachment), so we decided to revert the moves of IM3+IM4. 
• After redoing the green references and moving the IMs, we redid initial alignment and locked with a recycling gain of 47 before any ASC came on.

Noise in DARM:

Once we had the ASC engaged, we had no difficulty wiith moving to the nominal state (other than the violin mode).  However, we say very bad noise in DARM. 

• The fan was on in SQZT6, now turned off.
• Robert found that one of the new peaks in DARM has some coherence with HAM2 table motion. 
• We looked at some alignments in HAM2 because we were worried about clipping, and undid the large move of IM3 that happened last week. 
• After relocking Georgia moved IM3 more, while driving a line on IM3 yaw.  She was able to reduce the amplitude of the line in DARM and broad noise in DARM also was reduced, she will make a comment.

Other things today:

• ETMY mode6 (510.7264Hz) was very rung up when we first locked, and the guardian does not damp it.  We engaged damping with +60degrees and -0.1 gain, which seems to be working well and not yet ringing up ETMY MODE1, which is at 510.715Hz.
• We wanted to be able to close the POP beam diverter, so Craig moved the IFO trigger back to in vac POP.  (It had been changed to in air pop in 52150) 
• Craig trended the thresholds which used to be used for in vac POP, and we thought that the old threshold for POP in vac was a little close to the value of the PD, the trigger was set to 800 but with today's pretty good alignment the value sometimes drops to 860.  To avoid the possibility of this causing a lockloss in the future we lowered this to 700.  Craig also found several places in the guardian where this was hardcoded, so he moved them to lscparams and removed a redundant setting of the thresholds in PREP_DC_READOUT.
• We lost lock once from a glitch moving ADS, which was a cause of about 40 locklosses in O3a.  Since there are no integrators in the ADS servos, we decided to try limiting their outputs once we arrive in nominal low noise to prevent the large excursions from being sent to the ASC.