Thermo-elastic induced phase noise in the LISA Pathfinder spacecraft

TL;DR

This study assesses the thermo-elastic phase noise in the LISA Pathfinder spacecraft, demonstrating temperature stability and quantifying the impact of thermo-elastic distortions on the interferometer's phase noise.

Contribution

First experimental estimation of thermo-elastic phase noise contribution in the LISA Pathfinder's interferometer during thermal testing.

Findings

Temperature noise around 10^{-4} K/Hz^{1/2} in 1-30 mHz band

Thermo-elastic phase noise contribution estimated at 10^{-12} m/Hz^{1/2}

Thermo-elastic noise is 30 times below the measured noise at 1 mHz

Abstract

During the On-Station Thermal Test campaign of the LISA Pathfinder the data and diagnostics subsystem was tested in nearly space conditions for the first time after integration in the satellite. The results showed the compliance of the temperature measurement system, obtaining temperature noise around $10^{-4}\,{\rm K}\, {\rm Hz}^{-1/2}$ in the frequency band of $1-30\;{\rm mHz}$. In addition, controlled injection of heat signals to the suspension struts anchoring the LISA Technology Package (LTP) Core Assembly to the satellite structure allowed to experimentally estimate for the first time the phase noise contribution through thermo-elastic distortion of the LTP interferometer, the satellite's main instrument. Such contribution was found to be at $10^{-12}\,{\rm m}\, {\rm Hz}^{-1/2}$, a factor of 30 below the measured noise at the lower end of the measurement bandwidth ($1\,{\rm mHz}$).