High precision six-degree-of-freedom sensing plays an important role in future gravitational space missions. In gravitational or geodesy missions, measurements of all six degrees of freedom of freely floating test mass are required for reducing the cross-coupling noise, which is frequently an important limiting factor in the performance. Interferometry and capacitive sensing have been successfully combined in LISA pathfinder to achieve six degrees of freedom measurements. In this paper, we report a six-degree-of-freedom interferometer system based on multiplex differential wavefront sensing and longitudinal pathlength sensing. Compared to conventional capacitive sensing or optical levers, it has a higher measurement accuracy. The results of our table-top experiment show motion in all six degrees of freedom of a cubic test mass are simultaneously measured with a translational and tilt sensitivity of 100 pm/Hz^1/2 and 10 nrad Hz^−1/2 above 1 Hz, respectively. The translational dynamic range is greater than ±10 mm with nonlinear residuals less than 6 μm, and the tilt dynamic range is approximately ±500 μrad with nonlinear residuals less than 60 μrad. The coupling errors between multiple degrees of freedom are dominated by tilt-to-translation and tilt-to-tilt coupling, which are roughly 2–4 μm and 15–25 μrad, respectively, within a range of [−500 μrad, +500 μrad].

中文翻译：

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用于测试质量读数的高精度六自由度干涉仪

高精度六自由度传感在未来的引力空间任务中发挥着重要作用。在重力或大地测量任务中，需要测量自由浮动测试质量的所有六个自由度，以减少交叉耦合噪声，这通常是性能的重要限制因素。干涉测量和电容传感已成功地结合在 LISA 探路者中，以实现六自由度测量。在本文中，我们报告了一种基于多重差分波前传感和纵向光程传感的六自由度干涉仪系统。与传统的电容感应或光学杠杆相比，它具有更高的测量精度。^1/2和 10 nrad Hz ^-1/2分别高于 1 Hz。平移动态范围大于 ±10 mm，非线性残差小于 6 μm，倾斜动态范围约为±500μ非线性残差小于 60 的 radμ弧度。多自由度之间的耦合误差以倾斜平移和倾斜到倾斜耦合为主，大致为2-4 μ米和 15–25μrad，分别在[−500μ弧度，+500μ拉德]。