Sensor noise in LISA Pathfinder

Laser frequency noise and its coupling to the optical test mass readout

authored by
LISA Pathfinder Collaboration , M. Armano, H. Audley, J. Baird, P. Binetruy, M. Born, D. Bortoluzzi, N. Brandt, E. Castelli, A. Cavalleri, A. Cesarini, A. M. Cruise, K. Danzmann, M. De Deus Silva, I. Diepholz, G. Dixon, R. Dolesi, L. Ferraioli, V. Ferroni, E. D. Fitzsimons, R. Flatscher, M. Freschi, A. García, R. Gerndt, L. Gesa, D. Giardini, F. Gibert, R. Giusteri, C. Grimani, J. Grzymisch, F. Guzman, I. Harrison, M. S. Hartig, G. Hechenblaikner, G. Heinzel, M. Hewitson, D. Hollington, D. Hoyland, M. Hueller, H. Inchauspé, O. Jennrich, P. Jetzer, U. Johann, B. Johlander, N. Karnesis, B. Kaune, C. J. Killow, N. Korsakova, J. A. Lobo, J. P. López-Zaragoza, G. Wanner, S. Paczkowski, Jens Reiche, L. Wissel, A. Wittchen

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.

Institute of Gravitation Physics
PhoenixD: Photonics, Optics, and Engineering - Innovation Across Disciplines
Institute of Quantum Optics
External Organisation(s)
European Space Research and Technology Centre (ESTEC)
Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
Observatoire de Paris (OBSPARIS)
University of Trento
Airbus Group
Istituto Nazionale di Fisica Nucleare (INFN)
Fondazione Bruno Kessler
University of Urbino "Carlo Bo"
University of Birmingham
European Space Astronomy Centre
ETH Zurich
Royal Observatory
Bremen University of Applied Sciences
Autonomous University of Barcelona (UAB)
Institute of Space Studies of Catalonia (IEEC)
Texas A and M University
European Space Operation Center (ESOC)
Imperial College London
Heidelberg University
Universität Zürich (UZH)
University of Glasgow
Physical Review D
Publication date
Publication status
Peer reviewed
ASJC Scopus subject areas
Nuclear and High Energy Physics
Electronic version(s) (Access: Open)