J. Kissel

While trying to characterize problems with HEPI / TIDAL / ISI / ASC (LHO aLOGs 23676 and 23676), I tried taking a swept-sine transfer function with three data points between 0.001 and 0.005 to charaterize the HEPI / UIM cross-over frequency (recall that the TIDAL crossover frequencies were never calibrated beyond "roughly," LHO aLOG 16255). However, upon starting the excitation, DTT gave the IFO a good kick on lots of ASC and LSC DOFs. It did *not* break the lock, but it certaintly came close, and any higher an excitation amplitude would have certaintly lost it.

From a look at the time serious, it looks like DTT *tried* to ramp the signal, but chose a much faster ramp than is necessary for such a waveform.

Attached are the start of the waveform, a zoom in on the ramp, and then a screenshot of the DTT params.