Going back to Wiener filtering for a moment, I took a look at what the T240 noise level looks like in terms of pitch motion on one of our SOS optics (eg. PRM).
The selfnoise of the T240 (PSD, in dB referenced to 1m^2/s^4/Hz) was taken by pulling numbers from the Users Guide. This is the ideal noise floor, if our installation was perfect. I'm not sure where Kissel got the numbers from, but on page 13 of G1200556 he shows higher "measured" noise values for a T240, although his numbers are already transformed to m/rtHz.
To get the noise numbers to meters, I use: . The top of that fraction is (a) getting to magnitude from powerdB and (b) getting to asd units from psd units. The bottom of the fraction is getting rid of the extra 1/s^2.
Next I propagate this seismometer noise (in units of m/rtHz) to effective pendulum pitch motion, by propagating through the stacks and the transfer function for pos motion at the anchor point of the pendulum to pitch motion of the mirror (see eq 63 of T000134 for the calculation of this TF). This gives me radians/rtHz of mirror motion, caused by the ground motion:
.
I have not actually calibrated the POP QPD, so I will need to do that in order to compare this seismometer noise to my Wiener filter results.
