Actuation system of the inertial sensor for high-precision space missions using torsion pendulum

TL;DR

This paper presents a torsion pendulum setup to test and evaluate the actuation system of high-precision space inertial sensors, focusing on torque noise and control robustness essential for space missions.

Contribution

It introduces a novel ground testing method using a torsion pendulum to assess actuation system performance and control algorithms for space inertial sensors.

Findings

Maximum torque noise of 10^{-13} Nm/Hz^{1/2} at 1 mHz

Stable tracking error around 10^{-7}

Good robustness of the control system

Abstract

Precision space inertial sensors are imperative to Earth geodesy missions, gravitational wave observations and several fundamental physics experiments in space. In these missions, the residual acceleration noise of the test mass(TM) caused by the forces from inertial sensor components and environment is supposed to be kept below a certain level. As a number of forces contributing to residual acceleration are related to actuation system, developing a precise actuation system to exclude any erroneous force and obtain an ultra sensitive value for TM acceleration noise is necessary and essential. However, it is difficult to test the actuation system on ground. In this paper, a torsion pendulum is established to test the influence of actuation system on TM torque noise and a closed-loop control system combined torsion pendulum and parts of actuation modules is designed to assess the performance of actuation control algorithm. The experimental results show that the parameters in an actuation system will introduce additional torque noise and the maximum noise can reach as much as 10^{-13}Nm /Hz^{1/2} at 1 mHz. The stable tracking error for the closed-loop system is about 10^{-7}, indicating that the combination system achieves good tracking performance and robustness for TM rotation control in different conditions of inertial sensors.