This morning we had a combination of moderately high winds (gusts up tp 30-35 mph) and microseism above the 90% percentile, this is a combination of ground motion conditions where we had trouble durring O1.

We attempted to lock several times, and probably would have been able to if we had just kept trying, although we had random locklosses at diffrent stages of the CARM  offset reduction. 

One thing that we know is a weak point in our acquisition now is the ALS DIFF loop, so Matt and I had a look at improving that loop.  We saw that our UIM control filter, which has some modest plant inversion to make the crossover between the ESD and UIM stable, was not quite right.  We had features just above 2 Hz which were causing us to nearly have a second UGF there, and gain peaking was clearly visible in our control signals.  This was predicted by the sus model and our filters, although reality was a little worse than what was predicted.  

The first attached screnshot is the OLG before (blue) and after (red).  You can see that there was a small dip that nearly had multiple ugfs just above 2 Hz, which is improved a little.  THe second screenshot shows the crossover measured by injecting at L1, the third one shows the change to the filter. 

With this filter, we were no longer able to engage the 1 Hz resonant gain in the DARM filter bank.  From our model it isn't clear why that would be, but we also don't see any reason why we need such an aggressive ResG at the moment, so we are leaving it out.