Subtraction of temperature induced phase noise in the LISA frequency band

TL;DR

This paper demonstrates that temperature fluctuations significantly limit LISA Pathfinder measurements below 1 millihertz and presents a subtraction method that reduces this noise by over 15 dB, improving low-frequency gravitational wave detection.

Contribution

The paper introduces a novel noise subtraction technique for temperature-induced phase noise in gravitational wave detectors, validated on LISA Pathfinder data.

Findings

Temperature fluctuations limit measurements below 1 mHz.

Subtraction reduces noise by a factor of 5.6 at 10^{-4} Hz.

Noise reduction increases to 20.2 at 1.5×10^{-5} Hz.

Abstract

Temperature fluctuations are expected to be one of the limiting factors for gravitational wave detectors in the very low frequency range. Here we report the characterisation of this noise source in the LISA Pathfinder optical bench and propose a method to remove its contribution from the data. Our results show that temperature fluctuations are indeed limiting our measurement below one millihertz, and that their subtraction leads to a factor 5.6 (15 dB) reduction in the noise level at the lower end of the LISA measurement band 10^{-4} Hz, which increases to 20.2 (26 dB) at even lower frequencies, i.e., 1.5x10^{-5} Hz. The method presented here can be applied to the subtraction of other noise sources in gravitational wave detectors in the general situation where multiple sensors are used to characterise the noise source.