J. Kissel, T. Sadecki, B. Weaver
 
Betsy and Travis have finished up and are happy with new ITMX after BRD / NMBD installation yesterday (see 39239), so I grabbed a full suite of transfer functions to make sure the suspension is as expected in detail.

Attached are the results.

The message: both chains of the suspension look virtually identical to the prior build; they look spectacular.
If anything, I'm a little sad about the first Vertical mode (at 0.55 Hz) showing up in Transverse / Roll on the Reaction Chain (R0), where it has not before, but I'm confident this is simply exceptionally large vertical motion from the SUS being in air polluting the sensors' response. The coherence at those resonance points is minimal at best. There's otherwise no evidence of anything mechanically awry. 

We should definitely proceed with replacing the QUAD's stiffening sleeve and go forward with IFO alignment.