J. Kissel, H. Yu
WP 7730
ECR E1800201
IIET Ticket 10975

Given the recent apparent** success of BSC ISI ST2 to Top Mass feed forward with the QUADs (see LHO aLOGs 42875 and 42906), we've pushed a similar feed forward path into the beam splitter SUS's infrastructure to test out success there, to see if we want to modify the ECR to include this as well.

**I say apparent, only because we haven't yet measured the feed-forward's impact with any global sensors. Locally, it's a win!

A fair warning, this feed forward will be more interesting:
- Longitudinal for the beam splitter isn't just one Cartesian DOF as it is for the test masses, so we may need to figure out a way to actuate the ISI in longitudinal. Hopefully this can be done without a model change.
- Because of the back-reaction on the cage to ST2 of the ISI BS, we don't turn on ST2 isolation until well after we lock MICH in the IFO's acquisition sequence. Thus we should be sure to characterize the beam splitter with ST2 ON.

Attached are screen shots of the affected models and medm screens.
    /opt/rtcds/userapps/release/isi/h1/models/
        h1isibs.mdl
    /opt/rtcds/userapps/release/sus/h1/models/
        h1susbs.mdl
    /opt/rtcds/userapps/release/sus/common/models/
        BSFM_MASTER.mdl

    /opt/rtcds/userapps/release/sus/common/medm/bsfm/
        SUS_CUST_BSFM_OVERVIEW.adl
        SUS_CUST_BSFM_M1_ISIFF.adl