Both sensors of the SEIS instrument (VBBs and SPs) are mounted on the mechanical leveling system (LVL), which has to ensure a level placement on the Martian ground under currently unknown local conditions, and provide the mechanical coupling of the seismometers to the ground. We developed a simplified analytical model of the LVL structure in order to reproduce its mechanical behavior by predicting its resonances and transfer function. This model is implemented numerically and allows to estimate the effects of the LVL on the data recorded by the VBBs and SPs on Mars. The model is validated through comparison with the horizontal resonances (between 35 and 50 Hz) observed in laboratory measurements. These modes prove to be highly dependent of the ground horizontal stiffness and torque. For this reason, an inversion study is performed and the results are compared with some experimental measurements of the LVL feet’s penetration in a martian regolith analog. This comparison shows that the analytical model can be used to estimate the elastic ground properties of the InSight landing site. Another application consists in modeling the 6 sensors on the LVL at their real positions, also considering their sensitivity axes, to study the performances of the global SEIS instrument in translation and rotation. It is found that the high frequency ground rotation can be measured by SEIS and, when compared to the ground acceleration, can provide ways to estimate the phase velocity of the seismic surface waves at shallow depths. Finally, synthetic data from the active seismic experiment made during the HP3 penetration and SEIS rotation noise are compared and used for an inversion of the Rayleigh phase velocity. This confirms the perspectives for rotational seismology with SEIS which will be developed with the SEIS data acquired during the commissioning phase after landing.

中文翻译：

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SEIS 水准系统传递矩阵和共振的数值模型：在 SEIS 旋转地震学和动态地面相互作用中的应用

SEIS 仪器的两个传感器（VBB 和 SP）都安装在机械水准系统 (LVL) 上，该系统必须确保在目前未知的当地条件下将火星地面水平放置，并提供地震仪与地面的机械耦合. 我们开发了 LVL 结构的简化分析模型，以便通过预测其共振和传递函数来重现其机械行为。该模型以数字方式实现，可以估计 LVL 对火星上 VBB 和 SP 记录的数据的影响。该模型通过与实验室测量中观察到的水平共振（35 和 50 Hz 之间）进行比较来验证。这些模式被证明高度依赖于地面水平刚度和扭矩。为此原因，进行了反演研究，并将结果与​​ LVL 脚在火星风化层模拟物中的穿透的一些实验测量值进行了比较。该比较表明，该分析模型可用于估计 InSight 着陆点的弹性地面特性。另一个应用包括在 LVL 上的真实位置对 6 个传感器进行建模，同时考虑它们的灵敏度轴，以研究全局 SEIS 仪器在平移和旋转方面的性能。结果表明，高频地面旋转可以通过 SEIS 测量，并且与地面加速度相比，可以提供估算浅层地震面波相速度的方法。最后，比较 HP3 穿透和 SEIS 旋转噪声期间进行的主动地震实验的合成数据，并将其用于瑞利相速度的反演。这证实了 SEIS 旋转地震学的前景，该前景将利用着陆后调试阶段获得的 SEIS 数据进行开发。