As reported in elog2245, the AA noise level is in general higher than the noise of oplev from roughly 10Hz to 100Hz (looking at all Input/End pitch/yaw). This noise is suspected to come from PR/BS motion.

Therefore, the coherence check between PR/BS pitch/yaw excitation and AA signal was done. The result is shown in the attached figure 1-4. It can be seen that:

1. Compared with BS pitch excitation, all AA singals have high coherence between 10 and ~30Hz. (Fig 1)

2. Compared with BS yaw excitation, Input yaw shows the most coherence between several Hz to ~30Hz. (Fig 2)

3. Compared with PR pitch excitation, all AA signals have high coherence between ~30Hz to 100Hz. (Fig 3)

4. Compared with PR yaw excitation, Input yaw shows the most coherence between several Hz to ~30Hz. (Fig 4)

Besides, the AA signal with PR/BS local control loop open was also checked. The result is shown in the attached figure 5. It is clear that, the noise floor from ~10Hz to 100Hz becomes generaly lower. But there is no difference in End mirror yaw.