In order to investigate the source of the peak at 48 Hz in the sensitivity, we started injecting noise on WE marionette, which in the past has shown to be more reactive than the others at that frequency. As reference, we made the same injections on NE marionette.
As in the past, a vertical line excited the peak when it was injected on WE vertical, more than on NE. But injecting along the horizontal direction, the effect was the same for the two payload, and it was the same also injecting a similar line at 45 Hz (fig 1, fig 2). It is not what one migth expect if the peak was due to a WE marionette resonance (even vertical).
An alternative possibility is that the resonance belong to the F7 cage: the force on the marionette comes from F7 cage, and the vertical injection, weakly coupled to the sensitivity through the marionette, could find an easier path exciting a resonance of F7 cage or crossbar.
A campaign of noise injection on F7 from the ground actuators has been started, and the first results seem to confirm that hypothesys. A second log-entry will follow.
