Passive Method for Reducing Temperature Sensitivity of a Microelectromechanical Seismic Accelerometer for Marsquake Monitoring Below 1 Nano-g

Silicon-based accelerometers suffer from high temperature sensitivity due to the thermoelastic effect of silicon. In order to alleviate this effect for high-precision acceleration measurement, several technologies have been reported, including both active and passive approaches. However, the existing methods either use extra circuits and devices with more complexity and power consumption or affect the mechanical and electrical characteristics of the accelerometer suspensions. In order to eliminate those side effects, this paper introduces a passive approach, which applies silicon-solder-bilayer thermal actuators at the base of the suspension to passively compensate the thermally induced displacement of the accelerometer's proof mass, to reduce the thermoelastic response of the silicon-based accelerometers. The proposed thermal actuator based on the shrink-fit technology can provide stable bonding with silicon structures and leads to good agreement of the theoretical model with both the simulation and experimental results. The thermal actuator is applied to a micromachined vertical seismic accelerometer, which has a peak sensitivity of 0.3 x 10(-8) m S-2 (root Hz)(-1) for picking up seismic signals on Mars, to reduce its temperature sensitivity. Both the preliminary test of the displacement thermal response by a commercial laser displacement transducer and the thermal-cycling-experiment results with the readout electricity show that this passive method can reduce the temperature sensitivity of the silicon-based vertical seismic accelerometer by at least 2 orders of magnitude. By applying this technology and the wind and thermal shield (WTS), the overall temperature-related noise is 0.26 x 10(-8) m S-2 (root Hz)(-1) at 0.1 Hz, which is comparable to the intrinsic noise floor of the seismic accelerometer, meeting the mission's requirement. The temperature-compensated seismic accelerometer package has been used as the payload of the Interior Exploration using the Seismic Investigations, Geodesy, and Heat Transport (InSight) lander, which landed successfully on Mars on November 26, 2018, with the seismic accelerometers operating since Martian day (sol) 4.