This afternoon, after IAS verified the BBSS had not moved much, Mitch and I went up above and started unlocking the ISI to rebalance. This actually went pretty smoothly. Unlocked st2 after getting a locked reference position for the CPS and loosening the balance mass lock nuts, balanced the ISI, initially using just the raw vertical cps local readout in counts, then looking at the cartesian cps in Z,Rx&RY when the balance was close. When that was done, we pulled the screws holding the st1 balance masses and unlocked st1. Small adjustment on st1, relocked both stages, locked down balance masses again and unlocked one final time to check both stages were still good. Z I left a little high to account for buoyancy, RX and RY residuals were all under 10urad. RZ residuals were higher, I think we swung about 20 urad between locked and unlocked, but I think that measurement is less repeatable between lock and unlock. We re-locked the ISI and have some clean up tomorrrow, we put our removed balance masses on top of st2 under the cover, because we didn't have bags or labels.

Tomorrow we will replace the bad L4C on st1, unlock and do final checks. HEPI seemed to ring up when I tried turning on the loops this morning, I'm hoping that is because the ISI was locked and that was changing the HEPI plant or because of work in chamber, so that needs to verfied in addition to ISI close out tfs.