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The Site Tilt and Lander Transfer Function from the Short-Period Seismometer of InSight on Mars

Stott, Alexander E. and Charalambous, Constantinos and Warren, Tristram J. and Pike, William T. and Myhill, Robert and Murdoch, Naomi and McClean, John B. and Trebi-Ollennu, Ashitey and Lim, Grace and Garcia, Raphaël F. and Mimoun, David and Kedar, Sharon and Hurst, Kenneth J. and Bierwirth, Marco and Lognonné, Philippe and Teanby, Nicholas A. and Horleston, Anna and Banerdt, William B. The Site Tilt and Lander Transfer Function from the Short-Period Seismometer of InSight on Mars. (2021) Bulletin of the Seismological Society of America, 111 (6). 2889-2908. ISSN 0037-1106

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Official URL: https://doi.org/10.1785/0120210058

Abstract

The National Aeronautics and Space Administration InSight mission has deployed the seis- mic experiment, SEIS, on the surface of Mars, and has recorded a variety of signals includ- ing marsquakes and dust devils. This work presents results on the tilt and local noise sources, which provide context to aid interpretation of the observed signals and allow an examination of the near-surface properties. Our analysis uses data recorded by the short-period sensors on the deck, throughout deployment and in the final configuration. We use thermal decorrelation to provide an estimate of the sol-to-sol tilt. This tilt is exam- ined across deployment and over a Martian year. After each modification to the site, the tilt is seen to stabilize over 3–20 sols depending on the action, and the total change in tilt is < 0.035°. Long-term tilt over a Martian year is limited to < 0.007°. We also investigate the attenuation of lander-induced vibrations between the lander and SEIS. Robotic arm motions provide a known lander source in the 5–9 Hz bandwidth, yielding an amplitude attenuation of lander signals between 100 and 1000 times. The attenuation of wind sen- sitivity from the deck to ground presents a similar value in the 1.5–9 Hz range, thus favor- ing a noise dominated by lander vibrations induced by the wind. Wind sensitivities outside this bandwidth exhibit different sensitivity changes, indicating a change in the coupling. The results are interpreted through a finite-element analysis of the regolith with a depth- dependent Young’s modulus. We argue that discrepancies between this model and the observations are due to local compaction beneath the lander legs and/or anelasticity. An estimate for the effective Young’s modulus is obtained as 62–81 MPa, corroborating previous estimates for the top layer duricrust.

Item Type:Article
Audience (journal):International peer-reviewed journal
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Institution:Université de Toulouse > Institut Supérieur de l'Aéronautique et de l'Espace - ISAE-SUPAERO (FRANCE)
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Deposited On:11 Jan 2022 12:36

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