I have measured the HARD arm loops at several different input powers, so that we can see how the peaks move around with radiation pressure. Some of the measurements could be a bit better (eg. CHARD YAW 10W to lower freq), but I think it's enough that we get the idea of what's going on, and can confirm with the ASC model. 

For each plot, red is 20W, orange is 10W and blue is 2W.  Shaded regions indicate the ~1 sigma error bars from the coherence of the measurement.  The gains and control filters are different for each of these measurements, but I know what the state was, and the model script takes those differences into account.  I will also divide out the rest of the loop contributions, so that we can see how the suspension changes by itself.

For all of the loops except for DHARD Pitch, we have basically no gain in the frequency region that I had the patience to measure. We should look forward to using the confirmed ASC models to design sensible loops that have some actual gain.

The DHARD Yaw comparison with the model was reported in alog 25054, but I have not yet made the comparison plots for the other degrees of freedom.  The oplev damping is still being added to the quad suspension model, so it may be another little while before the pitch measurements get a model to compare with.

Attached as a tarball is a folder including the DTT templates for these measurements, the transfer functions and coherence text files exported from DTT, the matlab script to create the figures, and all of the figures saved in several different formats.  Note that the coherences that are exported into the text files are just the IN2/IN1 coherence, although others are available in the DTT templates.