(Josh Smith, Stefan Ballmer)

We estimated the IMC transmitted frequency noise due to the PSL intensity noise. The intensity noise explains the IMC frequency noise below 80Hz (the light discrepancy is likely due to me using ISS data from today). Interestingly, this noise also explains the HIFO-Y green readout noise between ~6Hz and ~50Hz (alog entry 7216).

At the time of data taking (7/25/2013, 06:23:53 UTC) the ISS was off, i.e. the MC RIN was high (plot 2).

Conversion:

IMC_trans_freq_noise = f0/L*PWR*(2+1+1)/c/mMC2/(2*pi*f)^2 * RIN

where
f0=2.818e14 Hz (red frequency)
L=16.4736 m    (IMC length, one way)
PWR=164 Watt   (Power in the IMC, = 1 Watt * Finesse/pi, Finesse=516)
mMC2=2.9kg     (Mass of MC2 mirror, same as for MC1 and MC2)
(2+1+1)        (effect of MC2 at 0deg, MC1 at 45deg, MC3 at 45deg)
f              (Audio frequency)