As Jeff posted last night, we've been working on doing Z tilt decoupling on the ISI's like Hugh and Krishna did back in 2014 (!) for the HEPIs in alog 15726. I followed a similar procedure to Hugh, getting tf's (with Jeff's help) driving in Z,RX and RY and dividing the Z to X/Y tfs by the RY/RX to X/Y tfs to get  the magnitude of the Z to RX/RY coupling. The calculated coefficients are then writtent into the Z->RX/RY cps2cart matrix elements. I still need to get the BS RY drive data and I need to do some close-out transfer functions to evaluate how good the decoupling is. Additionally, it looks like ETMY didn't need tilt decoupling in either dof, and ITMX & ETMX RX were also good.

The two attached plots are the ETMX & ITMX before and after Z drive to X transfer functions. These plots show the reduction in the magnitude of the coupling from Z to X, which implies that the magnitude of the Z to RY coupling has been reduced.

I've added all of my measurement data to the seismic svn at /ligo/svncommon/SeiSVN/seismic/BSC-ISI/H1/Common/Data/ Z_RX_RY_decouple, but its a couple hundred of megabytes of data.