We checked the coefficient between the RIN and the PZT of the laser. We swept from 1 kHz down to 10 Hz, but we only got good coherence below 20Hz. The measured value for H1:PSL-ISS_PD[AB]_OUT (Volts) / H1:IMC-F_OUT (kHz) at 10 Hz was –40 dB. Dividing by 10 V (ISS PD DC level) and multiplying by the measurement frequency of 0.01 kHz we get

RIN/rad = 10^–5.

The ISS inner and outer loops were off during the measurement.