Temperature-dependent modal analysis of the InSight lander on Mars

The first high-performance seismometer on Mars, deployed by InSight, has been working for nearly two Martian years. However, the recorded seismic data are substantially affected by the natural frequencies of the lander. To analyze the effect of the natural frequencies of the lander on specific components of the seismic data, we have built a simplified finite-element model of the lander to conduct modal analyses. Three natural frequencies are modeled by comparing them with those identified from the observed data. These natural frequencies are nonconstant and temperature dependent, which can be explained as an elastic modulus reduction of the solar panels (35% at most) and/or the property changes of the ground media beneath the lander due to a daily air temperature variation of approximately 100 K on Mars. Compared with the previous studies based on the empirical models before the launch, our results can quantitatively evaluate natural modes and their temperature dependency. Thus, these analyses are helpful in avoiding the potential interference of natural frequencies and improving the reliability of seismic data applications.