J. Kissel, S. Dwyer

Since we always seem to give Master Warner a hard time when he's just trying to do what we've asked, Shiela asked me to prove that commissioning HAM1 HPI, in attempts improve CHARD performance, is worth our time. As such, I attach a bunch of plots that supplement Jim's comparison of LLO vs. LHO HAM1 HEPI performance (see LHO aLOG 20538) taken while we're still trying to recover. I compare (regrettably uncalibrated) pitch and yaw ASDs of the REFL WFS against both the L4Cs in HAM1 and the GS13s in HAM3. We see that HAM1 is coherent with the features seen in the REFL WFS at 5-7 Hz and around the microseism -- which is a region which we can improve with HEPI inertial isolation -- and we see that our good ol' friend, the 0.6 [Hz] in HAM3, (see Integration Issue 1005) is coherent at ... 0.6 Hz, and indeed dominates a good fraction of total the RMS.

So, while the CHARD problem is complicated, because the REFL WFS contain CHARD motion, PR3 / PR2 motion, Input Beam Motion, some CSOFT, and their own motion, we can at least see that some protions of these signals can be improved if SEI were improved, which means we might be able to increase the bandwith of CHARD which would yield a more robust and stationary IFO.