Ground-Vibration Suppression by a Matched Center of Mass for Microthrust Testing in Spaceborne Gravitational-Wave Detection

High-precision and wide-band microthrust testing and evaluation on the ground is key to achieving precision, drag-free control, which is extremely demanding for spaceborne gravitational-wave detection missions. However, unlike a stable space environment, complex ground vibrations inevitably affect the evaluation of microthrust. To reduce the interference of ground vibrations, this paper proposes a sup-pression solution based on a hanging pendulum with an adjustable mass center. The theoretical analysis shows that the response of the pendulum to ground vibration can be effectively reduced with a matched mass center. The dual-frequency modulation experiment verified the linear relationship between vibration noise and mass-center-to-swing-point distance. By setting the mass-center distance from the swing point to 0.2 mm, the noise of the sub-micro-Newton balance is better than 0.1 mu N Hz-1/2 from 6 mHz to 20 Hz. This method effectively suppresses the interference of ground vibration, which helps us to obtain an accu-rate microthrust model for space gravitational-wave missions, while providing a solution for weak-force, ground testing over wide-band frequencies.