Charge-Induced Force Noise on Free-Falling Test Masses: Results from LISA Pathfinder

Area of Science:

• Space physics
• Gravitational wave detection
• Electrostatics

Background:

• Space-based gravitational wave detectors require extremely precise measurements.
• Electrostatic forces on test masses are a significant noise source.
• LISA Pathfinder (LPF) is a mission to test technologies for future detectors.

Purpose of the Study:

• To measure and mitigate charge-induced electrostatic forces on test masses in LPF.
• To assess the noise level in a relevant space environment.
• To validate electrostatic models for space-based detectors.

Main Methods:

• In-flight electrostatic measurements on free-falling test masses.
• Charge control and electric-field compensation techniques.
• Analysis of differential acceleration between test masses.

Main Results:

• Charge-induced acceleration noise maintained near 1.0 fm/s²/Hz in the 0.1-100 mHz band.
• Stochastic TM charge buildup due to cosmic rays identified.
• Charge-to-force coupling through stray electric fields quantified.

Conclusions:

• Electrostatic noise can be managed to levels suitable for gravitational wave observatories.
• LPF measurements validate electrostatic models.
• Results are critical for the Laser Interferometer Space Antenna (LISA) mission.