Tilt-to-length coupling in LISA—uncertainty and biases

authored by: M. S. Hartig, J. Marmor, D. George, S. Paczkowski, J. Sanjuan
Abstract: The coupling of the angular jitter of the spacecraft and their sub-assemblies with the optical bench and the telescope into the interferometric length readout will be a major noise source in the LISA mission. We refer to this noise as tilt-to-length (TTL) coupling. It will be reduced directly by realignments, and the residual noise will then be subtracted in post-processing. The success of these mitigation strategies depends on an accurate computation of the TTL coupling coefficients. We present here a thorough analysis of the accuracy of the coefficient estimation under different jitter characteristics, angular readout noise levels, and gravitational wave sources. We analyze in which cases the estimates degrade using two estimators, the common least squares estimator and the instrumental variables estimator. Our investigations show that angular readout noise leads to a systematic bias of the least squares estimator, depending on the TTL coupling coefficients, jitter and readout noise level, while the instrumental variable estimator converges to an unbiased result as the data set length increases. We present an equation that predicts the estimation bias of the least squares method due to angular readout noise.
Organisation(s): Institute of Gravitation Physics
External Organisation(s): Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
University of Florida (UF)
University of Arizona
Texas A and M University
Type: Article
Journal: Classical and quantum gravity
Volume: 42
ISSN: 0264-9381
Publication date: 24.01.2025
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Physics and Astronomy (miscellaneous)
Electronic version(s): https://doi.org/10.1088/1361-6382/ada866 (Access: Open)

BibTeX

@article{88c6140feea34391979a2c8d38ccce69,
title = "Tilt-to-length coupling in LISA—uncertainty and biases",
abstract = "The coupling of the angular jitter of the spacecraft and their sub-assemblies with the optical bench and the telescope into the interferometric length readout will be a major noise source in the LISA mission. We refer to this noise as tilt-to-length (TTL) coupling. It will be reduced directly by realignments, and the residual noise will then be subtracted in post-processing. The success of these mitigation strategies depends on an accurate computation of the TTL coupling coefficients. We present here a thorough analysis of the accuracy of the coefficient estimation under different jitter characteristics, angular readout noise levels, and gravitational wave sources. We analyze in which cases the estimates degrade using two estimators, the common least squares estimator and the instrumental variables estimator. Our investigations show that angular readout noise leads to a systematic bias of the least squares estimator, depending on the TTL coupling coefficients, jitter and readout noise level, while the instrumental variable estimator converges to an unbiased result as the data set length increases. We present an equation that predicts the estimation bias of the least squares method due to angular readout noise.",
keywords = "gravitational waves, instrument noise, laser interferometer space antenna, performance analysis, tilt-to-length coupling",
author = "Hartig, {M. S.} and J. Marmor and D. George and S. Paczkowski and J. Sanjuan",
note = "Publisher Copyright: {\textcopyright} 2025 The Author(s). Published by IOP Publishing Ltd.",
year = "2025",
month = jan,
day = "24",
doi = "10.1088/1361-6382/ada866",
language = "English",
volume = "42",
journal = "Classical and quantum gravity",
issn = "0264-9381",
publisher = "IOP Publishing Ltd.",
number = "4",
}