A composite evaluation method of sub-micro newton thrust in 0.1 mHz to 10 Hz ultra-wide frequency range for TianQin

Abstract

Space-based gravitational wave detection requires inertial reference with a residual acceleration noise below $10^{-15}m{s}^{-2}{\mathrm{Hz}}^{-1/2}$, achieved by constructing high-precision drag-free satellites. Sub-micro Newton thrusters serve as actuation mechanisms for high-precision drag-free control to counteract external non-conservative forces on spacecraft. Pre-launch performance test and evaluation on the ground are crucial. However, achieving sub-micro Newton thrust noise in the frequency range of 0.1 mHz to 1 Hz, along with a rapid thrust response of 10 Hz, presents significant challenges for high-precision ground testing and evaluation. In this study, a unified method for weak force calibration evaluation will be established using electrostatic force, combining high resolution torsion pendulum and wide frequency range pendant pendulum test setups. Dynamic transfer function calibration of the two systems will be conducted in different frequency ranges. Ultimately, through composite testing and unified calibration of the two thrust testing systems, the ability to evaluate thrust noise at 0.1 $\mu$N${\mathrm{Hz}}^{-1/2}$ in the ultra-wide range of $10^{-4}$ $\sim$10 Hz is achieved. It will provide technical support to the ground micro-thrust testing for space-based gravitational wave detection as TianQin.