After the angle calibrations were applied to the SPI readout channels, I grabbed some data to check whether the SPI is roughly agreeing with the ISI sensors. I used the supersensor OUT channels for the ISI sensors (these are the signals behind the blending filters, before the summation for the blended supersensor). Screenshots from diaggui are attached.

For the differential X degree of freedom (SPI length), the visual agreement is remarkably good.

The optical lever (angle) measurements are harder to interpret. First of all, QPD A has an as-yet-unresolved noise issue, which Jennie is currently investigating. Aside from this, the results look very encouraging, since the CPS and GS13 at least somewhat agree with the SPI.

These spectra should be regarded as a first result, but not yet final. We will post a better analysis once the error has been resolved.

Note: If anyone has suggestions for which sensor channels would provide a better/more appropriate comparison than the supersensor OUT channels used here, please comment, your input is welcome.