[Lucia, Terrence]

Following 14790, we have turned off the redundant DCcut filter in the geophone input filters and moved the 0.01 cutoff in the calibration filter to 0.003 to improve phase performance at 0.1 Hz. We diagonalized the geophones by matching the transfer functions as measured by the LVDTs and minimizing coupled resonance peaks. Then we estimated noise of the lvdt+seismometer and geophone noise. After that, I optimized a complementary by minizing the integrated RMS of the resultant noise spectrum. Results are shown in figures below. As can be seen, the blending frequencies are quite high. The situation will be different if we include seismic noise in the lvdt noise. I will synthesize those filters later just in case sensor correction is not available. We have copied the control filters in the DAMP filter to the IDAMP filter and enabled inertial damping.