While the EQ has the IFO down for a time, took TFs to check the TILT decoupling on the ISI to see if the coupling was bad.

When we blend the inertial sensors into the super sensor at lower frequencies, we must make sure there is no tilt coupling.  The tilting inertial sensor will inject the tilt into the platform motion, obviously not a good thing.

First attached is a look at the saved plot from decoupling Jim or I did way back; the decoupling factors have been the same numbers for over a year (I checked conlog, thank you Patrick.)

The blue curve is the final decoupled TF between X drive and T240 response. The Red curve is with no decoupling.  Fairly clear: the coupling is showing up below 60mHz and that the decoupling factors do a very good job of eliminating the tilt--a nice linear trace down to DC is what you want.

The second attachment is the current  measurement showing that the tilt decoupling is still very good.  The blue trace is the original value (same as above) and the red and black traces are with the 45 and 90mHz blends respectively.  The blend should not matter when looking for the decoupling but the 7.1Mag EQ gave the time so I ran both.

Now I do see some yuck in the 30-70mHz band but these are only 3 averages and the blue trace is 10 averages so that may be the reason for the yuck.