Preliminary Design of a Passive System for Monitoring Volcanic Emissions Exploiting Microwave GEO Satellite Downlinks

Opportunistic sensing based on microwave satellite downlinks has recently gained attention as a cost‑effective approach for monitoring tropospheric phenomena, exploiting the attenuation experienced by communication signals as they propagate through the atmosphere. While this approach has been successfully applied to meteorological phenomena—particularly rainfall estimation using Ku‑band broadcasting links and, more recently, Ka‑band broadband services—its use for geophysical monitoring remains largely unexplored.  Volcanic emissions, in particular, release atmospheric constituents capable of significantly affecting microwave propagation through absorption and scattering, depending on particle size, concentration, and chemical composition. In regions surrounding active volcanoes, the interaction between ash, gases, and microwave signals offers an opportunity to detect eruptive activity using low‑cost ground receivers.

This work investigates the feasibility of using commercial satellite downlink signals to sense volcanic emissions in real time. The analysis considers the general interaction between microwave signals and volcanic constituents and examines how the Ku‑ and Ka‑band frequencies commonly used by GEO satellites provide different levels of sensitivity to these atmospheric components. Since these signals are continuously available over wide areas, they offer an attractive resource for passive and inexpensive monitoring.

A key aspect in assessing the feasibility of such opportunistic sensing is the geometry of the satellite–receiver link, which strongly influences the detectability of volcanic emissions. As matter of fact, the relative position of the satellite, the ground station, and the volcanic plume determines whether the microwave path intersects the cloud and at which altitude and distance from the vent this intersection occurs. In volcanic regions such as Mount Etna (Italy), the simultaneous visibility of multiple GEO satellites at different azimuths and elevations increases the likelihood that at least one downlink path crosses the plume, enabling the detection of its impact on the received signal.

This preliminary study provides thus a first assessment of the geometric and physical conditions under which satellite downlink signals can be exploited for volcanic emission detection.

The results suggest that existing broadcast satellite infrastructure could be leveraged also as a low‑cost, wide‑area monitoring system, complementing conventional geophysical instruments and motivating future experimental validation.

Acknowledgements: This work was supported by the following projects: Space It Up, funded by Italian Space Agency (ASI) and the Italian Ministry of University and Research (MUR) – Contract 2024-5-E.0 - CUP I53D24000060005; FoReLab (Departments of Excellence), funded by MUR.