In Ushiba-san’s transfer function measurement from OMC length error to DARM, the dither value used to obtain the OMC error signal was 300 counts. On the other hand, the dither count when we acquired the OMC error signal was 400. When the dither value is increased, the sensing factor of the OMC increases, which means that the error signal of the OMC also increases. Thus, the transfer function (DARM/OMC error) is corrected by a factor of 3/4. The results of the projection onto DARM with this correction are shown below.

I found and corrected a mistake in the projection of geophone noise onto the DARM sensitivity.

In the previous analysis, the transfer function from the OMC error signal to the DARM sensitivity was linearly interpolated to match the number of the geophone noise data. At that time, I ensured the frequency range and number of data points matched. However, I had overlooked the frequency vector of the transfer function from DARM to the OMC error, which was logarithmic. The geophone noise and the transfer function from the geophone to the OMC error signal are obtained at linearly spaced frequencies. In other words, I had been combining data with a linear interval and data with a logarithmic scale, which only matched the number of data points and frequency range.
The projection onto DARM after the correction is shown in the attached figure.