Autocorrelation infrasound interferometry for atmospheric sensing on Earth and Mars

We develop a framework for retrieving time-varying atmospheric properties using a single infrasound sensor following an autocorrelation interferometry method. We compare relative velocity (effective sound speed) changes inferred from infrasound autocorrelations with independently measured air temperature and velocity variations. For the propagation geometry of the infrasound source (a waterfall) and receivers at El Reventador (Ecuador) we infer that effects from wind velocity can be assumed negligible and provide a mathematical model to derive temperatures from relative velocity changes. We further demonstrate that the autocorrelation method can be used to study the Martian atmosphere; specifically, we show that relative velocity changes derived from the pressure sensor on board the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport lander can track variations of the effective speed of sound. These results also suggest the presence of continuous background infrasound on Mars.

References:

• Ortiz, H. D., Matoza, R. S., Johnson, J. B., Hernandez, S., Anzieta, J. C., and Ruiz, M. C. (2021). Autocorrelation infrasound interferometry. Journal of Geophysical Research: Solid Earth. https://doi.org/10.1029/2020JB020513
• Ortiz, H. D., Matoza, R. S., and Tanimoto, T. (2022).  Autocorrelation infrasound interferometry on Mars. Geophysical Research Letters. https://doi.org/10.1029/2021GL096225