GNSS signals have traditionally been used for positioning and navigation, but this work highlights how analyzing their reflections from Earth's surface can extend their value into large-scale Earth observation. By listening for reflected radio frequency signals rather than transmitting dedicated radar pulses, Spire's satellites can provide persistent coverage that is independent of sunlight and largely unaffected by weather conditions. This capability is particularly important in the Arctic, where darkness and cloud cover often limit the performance of optical sensors and where environmental change is accelerating.
The GNSS-Reflectometry approach used by DGFI-TUM and the Norwegian Research Centre leverages miniaturized RF payloads, advanced digital signal processing, and machine learning algorithms to retrieve sea ice freeboard, the height of ice above the waterline. By processing large volumes of reflections collected across the Arctic, the researchers were able to generate continuous freeboard maps spanning the winter season, enabling a detailed view of sea ice conditions over time. The strong agreement with CryoSat and other reference datasets indicates that this technique can provide reliable measurements suitable for scientific and operational use.
Spire operates a fully deployed satellite constellation designed to observe Earth in real time using radio frequency sensing. In addition to GNSS-Reflectometry for cryosphere and ocean applications, the company collects RF data to support global weather intelligence, ship and aircraft tracking, and the detection of spoofing and jamming activities that can affect navigation and communications systems. These data products are used to improve forecasts, monitor transportation networks, and understand how environmental and human-driven changes interact at a global scale.
According to Spire Chief Executive Officer Theresa Condor, recent advances have expanded what is feasible with RF sensing from commercial platforms. "Advances in miniaturization, digital signal processing, and machine learning have fundamentally changed what's possible in RF sensing," she said. "Commercial constellations can now deliver persistent, high-quality RF data that complements traditional government systems with greater flexibility and cost efficiency. As environmental monitoring requirements intensify, we're seeing agencies increasingly integrate commercially sourced RF datasets into operational architectures, reflecting the continued maturation of this market and the growing role of commercial infrastructure in government missions."
The Arctic sea ice research supported by ESA's Third Party Missions programme exemplifies this trend by integrating commercial GNSS-R observations with established scientific missions. ESA's CryoSat mission has long provided detailed measurements of ice thickness and freeboard, and the new work shows how additional RF data streams can enhance spatial and temporal coverage. By tapping into commercial constellations, agencies can scale up monitoring efforts without bearing the full cost and development burden of deploying new dedicated satellites.
Beyond the cryosphere, the same GNSS-Reflectometry methods can be used to study ocean roughness, soil moisture, and other surface properties that influence climate and weather. Persistent RF listening from space allows scientists and operational agencies to track changes in near real time across large and remote areas, including polar regions and open ocean basins. As processing techniques and models continue to improve, these multi-use RF datasets are expected to feed into a broader range of services, from maritime routing and fisheries management to disaster response and infrastructure planning.
Related Links
Spire Global Inc
Beyond the Ice Age
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