Keita, Sheila, Terra
We have had 3 locklosses today caused by saturations of the ISS 1st loop. There are 2 main messages from this alog:
- ISS diffracted power has been drifting lower and has been adjusted (REF level moved from -1.6 to -1.53, diffracted power now around 3.8%) . There is a test for ISS diffracted power in DIAG main, but it was compalining today that the diffracted power was too high (rather than too low). The first attached trend shows a 2 week trend of the diffracted power, the second shows the DIAG main log from today.
- It looks as though the ISS autolocker might not be helping us (it might be hurting us)
Earlier today, Keita and I had a look at the logic in the ISS autolocker. It seems that it watches the channel H1:PSL-ISS_TRANSFER1_B_OUTPUT, if this is above H1:PSL-ISS_SAT_THRES (currently set to 5 V) for more than 10 seconds, it opens the first loop. In the third attached screnshot you can see this in action right before one of our locklosses. At just after -14 seconds, TRANSFER1B (bottom row) becomes large and the AOM DRIVER monitor (top right) flatlines. The PD sums become slightly more noisy for 10 seconds, after which the ISS is opened by the autolocker. This causes the PD sums to become much noisier, and the hugh glitch in power visible in IM4 TRANS. Is there any gentler way to deal with a saturation?
