On Monday Shoshana and Jim took a low-resolution tilt Ry-Ry TF of HAM3 with the ISI in the damped state (Shoshana will post another alog focused on the CRS). We included the SPI QPDA PIT on this measurement to get a sense if it's measuring HAM3 pitch, as we expect.
After applying a calibration gain of 240urad/cts (and a minus sign, and the antiwhitening filter from 91157) on the oplev signal, the transfer function matches the one for the CPS and CRS well at low frequencies. This is a good first order validation that QPD A Pitch is sensing HAM3 Tilt.
I also took a spectrum comparing the SPI QPD A (with applied calibration from above) and compared the ambiant spectra with the CRS and GS13 on HAM3.
The time used for this analysis was during the SC test from this last weekend (91111), with both HAM2 and HAM3 ISI isolated, and after the beam was recentered on the QPD (91124).
The SPI spectra looks like it is not measuring the ISI ambient tilt. The spectra looks flat and there is little to no coherence with either the GS13 or the CPS from HAM3. Assuming this is noise, it seems 100x higher than the expected noise from p20 of G2301177 (few*1e-10rad/rtHz)
The template for this measurement lives under : /ligo/svncommon/SeiSVN/seismic/HAM-ISI/H1/HAM3/CRS/Templates/dtt/CRS_SPI_spectra_071826.xml