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fabian.arellano - 16:13 Tuesday 30 July 2019 (9697) Print this report
Residual motion of the optic in ALIGNED and FLOAT states.

Today I measured the residual motion of the optic in ALIGNED and FLOAT states.

In both states the optic RMS displacment and velocity fulfills the requirement, which suggests that turning the control system off for the payload during observation time should be fine if considered necessary. It's worth mentioning the main interferometer team wants to have some sort of local control system for the payload during observation time, but the details still have to be decided.

This table shows the integrated RMS displacement for each degree of freedom and the requirement.

Degree of freedom ALIGNED FLOAT Requirement
Longitudinal displacement  0.1 µm  0.1 µm  0.4 µm
Longitudinal velocity 0.14 µm/s 0.2 µm/s 0.5 µm/s
Pitch displacement  0.07 µrad 0.09 µrad 1 µrad
Yaw displacement  0.07 µrad 0.3 µrad 1 µrad


  • There is no inertial damping.
  • Directory: /kagra/Dropbox/Subsystems/VIS/TypeBData/BS/Noise/Measurements/20190730/
  • File for ALIGNED state: BS_ALIGNED_TM_OPLEV_ASD_190730_1564467416.xml
  • File for FLOAT state: BS_FLOAT_TM_OPLEV_ASD_190730_1564468574.xml
  • Bandwidth of the displacement measurement: from 0.010 Hz to 800 Hz.
  • The bandwidth of the optic velocity measurement was from 0.010 Hz to 10 Hz. Above 10 Hz there is a lot of noise which I don't believe is real displacement of the optic. Peaks are likely related to the oplev optics support platform.
  • Related entries: 8945, 9456.
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