TY - JOUR

T1 - Tilt-to-length coupling in LISA Pathfinder: Analytical modeling

AU - Hartig, Marie Sophie

AU - Wanner, Gudrun

N1 - Funding Information: We thank Valerio Ferroni and Nikolaos Karnesis for valuable discussions. This work was made possible by funds of both the German Space Agency, DLR, and the Deutsche Forschungsgemeinschaft (DFG). We gratefully acknowledge the German Space Agency, DLR and support by the Federal Ministry for Economic Affairs and Climate Action based on a resolution of the German Bundestag (Grants No. FKZ 50OQ0501, No. FKZ 50OQ1601, and No. FKZ 50OQ1801). Likewise, we gratefully acknowledge the Deutsche Forschungsgemeinschaft (DFG) for funding the Cluster of Excellence QuantumFrontiers (Grant No. EXC 2123, Project ID 390837967).

PY - 2023/7/26

Y1 - 2023/7/26

N2 - Tilt-to-length coupling was the limiting noise source in LISA Pathfinder between 20 and 200 mHz before subtraction in postprocessing. To prevent the adding of sensing noise to the data by the subtraction process, the success of this strategy depended on a previous direct noise reduction by test mass alignment. The exact dependency of the level of tilt-to-length coupling on the set points of LISA Pathfinder's test masses was not understood until the end of the mission. Here, we present, for the first time, an analytical tilt-to-length coupling model that describes the coupling noise changes due to the realignments. We report on the different mechanisms, namely the lever arm and piston effect as well as the coupling due to transmissive components, and how they contribute to the full coupling. Further, we show that a pure geometric model would not have been sufficient to describe the coupling in LISA Pathfinder. Therefore, we model also the nongeometric tilt-to-length noise contributions. For the resulting coupling coefficients of the full model, we compute the expected error bars based on the known individual error sources. Also, we validated the analytical model against numerical simulations. A detailed study and thorough understanding of this noise are the basis for a successful analysis of the LISA Pathfinder data with respect to tilt-to-length coupling.

AB - Tilt-to-length coupling was the limiting noise source in LISA Pathfinder between 20 and 200 mHz before subtraction in postprocessing. To prevent the adding of sensing noise to the data by the subtraction process, the success of this strategy depended on a previous direct noise reduction by test mass alignment. The exact dependency of the level of tilt-to-length coupling on the set points of LISA Pathfinder's test masses was not understood until the end of the mission. Here, we present, for the first time, an analytical tilt-to-length coupling model that describes the coupling noise changes due to the realignments. We report on the different mechanisms, namely the lever arm and piston effect as well as the coupling due to transmissive components, and how they contribute to the full coupling. Further, we show that a pure geometric model would not have been sufficient to describe the coupling in LISA Pathfinder. Therefore, we model also the nongeometric tilt-to-length noise contributions. For the resulting coupling coefficients of the full model, we compute the expected error bars based on the known individual error sources. Also, we validated the analytical model against numerical simulations. A detailed study and thorough understanding of this noise are the basis for a successful analysis of the LISA Pathfinder data with respect to tilt-to-length coupling.

UR - http://www.scopus.com/inward/record.url?scp=85166743345&partnerID=8YFLogxK

U2 - 10.48550/arXiv.2305.03667

DO - 10.48550/arXiv.2305.03667

M3 - Article

AN - SCOPUS:85166743345

VL - 108

JO - Physical Review D

JF - Physical Review D

SN - 2470-0010

IS - 2

M1 - 022008

ER -