Sensor noise in LISA Pathfinder: Laser frequency noise and its coupling to the optical test mass readout
Abstract
The LISA Pathfinder (LPF) mission successfully demonstrated the feasibility of the technology needed for the future space borne gravitational wave observatory LISA. A key subsystem under study was the laser interferometer, which measured the changes in relative distance in between two test masses (TMs). It achieved a sensitivity of 32.0₋₁.₇⁺².⁴ fm / √Hz, which was significantly better than the prelaunch tests. This improved performance allowed direct observation of the influence of laser frequency noise in the readout. The differences in optical path lengths between the measurement and reference beams in the individual interferometers of our setup determined the level of this undesired readout noise. Here, we discuss the dedicated experiments performed on LPF to measure these differences with high precision. We reached differences in path length difference between (368 ± 5) μm and (329.6 ± 0.9) μm which are significantly below the required level of 1 mm or 1000 μm. These results are an important contribution to our understanding of the overall sensor performance. Moreover, we observed varying levels of laser frequency noise over the course of the mission. We provide evidence that these do not originate from the laser frequency stabilization scheme which worked as expected. Therefore, this frequency stabilization would be applicable to other missions with similar laser frequency stability requirements. Show more
Permanent link
https://doi.org/10.3929/ethz-b-000661679Publication status
publishedExternal links
Journal / series
Physical Review DVolume
Pages / Article No.
Publisher
American Physical SocietySubject
Gravitational wave detection; Metrology; Noise; Optics & lasers; Laser applications; Data analysis; Gravitational wave detectors; Optical interferometry; Satellite data analysisFunding
ETH-05 16-2 - LISA Pathfinder sensing and actuation data analysis and the route to LISA (ETHZ)
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