In December, I suggested a design for a new sensor correction filter for LHO. For most of the last month the end station ISI's have been running running this for a while, but I haven't had a good opportunity to do any comparisons of the interferometers performance. For now, I'll summarize the changes to the end station's configuration. During O1, we used 90 or 45mhz blends on St1 X&Y (depending on microseism) and the .46hz sensor correction (stolen from LLO) from the ground STS to St1 CPSs. For a good portion of the last month, I've been running the end station ISIs with my useism sensor correction to St1 and I moved the .46hz sensor correction to St2. I think that this configuration has allowed us to use the 90mhz blends with higher microseism, but I still haven't come up with a measurement to show that.

My first two attached plots show the difference in X between these two configurations. The first plot is the St1 perfromance (T240's blue and red) and  ground STS (pink and light blue). Dashed is with the "01" configuration, solid is with the current configuration. As expected the current performance loses some around .5hz, but  gains a factor of 2-ish suppressio of the microseism. The second plot shows the St2 GS13s and ground. Green is the current configuration, brown is the O1 configuration. The current configuration (useism senscor on st1, and st1-2 senscor) does better most places except for some gain peaking around 50-60mhz. It would be useful to compare the current configuration to performance with the 45mhz blends, which suppress the microseism better, but have more gain peaking below 100mhz and are adversely affected by wind.

The last plot shows the suppression (the transfer function from the ground STS to the St2 GS13s) of the 01(dashed brown)  and current (solid blue) configuration. The story is the same, the current configuration does a better job between .1 and ~1 hz, a bit worse below .1 hz.

I have more configuration stuff to log, but I'm out of time for the moment. But HAM1 has inertial isolation, and I've added St1-2 FF in Z to the BSCs.