J. Kissel, R. Lane

Just as a sanity check, we took a measurement of TOP to TOP transfer functions on the Main Chain, to ensure we didn't induce rubbing after cabling up the reaction chain. Pitch shows a curious drop in magnitude by a factor 0.6 rad/N.m, but the other degrees of freedom are reproduced identically (see "allquads" attachment). Several explanations for the drop in magnitude are possible. Things we can rule out:
 (1) As was mentioned earlier, we did replace F2 OSEM on Teusday 8/09 after noticing it had died after the power outage. However, we measured before (2011-08-04) and after (2011-08-10), and found no difference between the two measurements.
 (2) Drive amplitude for the (DTT) Pitch TF was lower. Nope -- checked the saved DTT templates for all three measurements ... 150 cts everytime

Most likely suspect:
 (3) Some mechanical misalignment of the F1 OSEM. Comparison between Pitch Drive and F1, F2, and F3 response (see PtoOSEM) show that F1's response has been reduced by the same amount.

Again, since the dynamics appear unchanged (Pitch resonant frequencies have not moved, nor changed Q, all other degrees of freedom are unchanged), this is not a show stopper. We'll have to re-align these OSEMs 20 more times before the QUAD enters the chamber. So we march forward on into the fog, of attempting to turn on the lower stages.