Tilt-induced Noise Improvement of a Nano-g MEMS Accelerometer for Lunar Seismograph with Omnidirectional Deployment

China’s Lunar Exploration plans to deploy Lunar Seismograph on the moon’s surface to detect moon-quakes. Given the unknown inclination angle of the lunar landing, it is important that these sensors possess the capability to adapt to different slopes. This article introduces a MEMS accelerometer that is capable of automatic levelling with omnidirectional deployment. Unlike traditional high-precision accelerometers, which require manual or motorized levelling at a large tilt angle, this accelerometer achieves levelling without any mechanical levelling system. Within this paper, a precise theoretical noise model is established, and by measuring each noise source against their theoretical noise gains, a total theoretical noise floor is calculated. The theoretical noise floor aligns perfectly with the actual measured noise floor, validating the correctness of the model. The noise tests indicate a noise floor reaching 3 ng/sqrt(Hz) @1-30Hz, with low-frequency noise performance achieving 20 ng/sqrt(Hz) @0.01Hz. The dual-axis turntable tests demonstrate that the accelerometer can work at any angle. Furthermore, it clearly detected earthquake signals of M5.5 from distances over 2000 km, matching the signals detected by a co-located commercial seismometer with residual of 8.6 ng. This article provides new insights into the levelling system design of subsequent MEMS accelerometer or seismometer.