NASA's GUARDIAN system spots tsunami-triggered atmospheric waves within minutes. This near-instantaneous monitoring enables earlier warnings and could lead to a new approach to global hazard sensing.
In late July, a magnitude 8.8 earthquake off Russia’s Kamchatka Peninsula triggered a tsunami across the Pacific, giving NASA’s experimental tsunami detection tool, GUARDIAN, a rare and critical real-world test.
Developed by the Jet Propulsion Laboratory (JPL), GUARDIAN (Global Navigation Satellite Systems Upper Atmospheric Real-Time Disaster Information and Alert Network) uses satellite data to detect atmospheric signals generated by tsunamis. A key component of the system was installed just one day before the earthquake hit.
Within 20 minutes of the seismic event, GUARDIAN detected pressure waves in the upper atmosphere and issued alerts up to 40 minutes before the tsunami reached Hawaii and other parts of the Pacific on July 29. Although the system’s outputs still require expert interpretation, this ability to produce data snapshots within 10 minutes makes GUARDIAN one of the fastest tsunami detection tools available today.
What GNSS Brings to Natural Hazard Detection
GUARDIAN is powered by data from Global Navigation Satellite Systems (GNSS), which include satellite constellations, ground control networks, and receivers used to determine precise locations via trilateration. These systems are foundational for Positioning, Navigation, and Timing (PNT) services used across a wide range of sectors, from aviation and maritime transport to telecommunications, emergency response, and finance.
Currently, fully operational GNSS systems include the United States’ GPS and Russia’s GLONASS, with China’s BeiDou and Europe’s Galileo in development. These systems could soon offer signals from more than 100 satellites, enabling highly accurate, global positioning and monitoring capabilities.
How GUARDIAN Works
GUARDIAN is an advanced, near-real-time software platform designed to enhance tsunami and disaster early warning systems. It monitors Total Electron Content (TEC) in the ionosphere to detect atmospheric disturbances caused by natural or human-made events. These disturbances, often triggered within eight to 10 minutes of an undersea earthquake, cause changes in the upper atmosphere that GNSS signals can detect.
The software processes this data and generates TEC time series within about 10 minutes, offering some of the fastest monitoring capabilities currently available. This places it just behind the initial seismic event, meaning GUARDIAN is fast enough to provide valuable early warnings, especially in distant, or far-field, tsunami scenarios.
By analyzing the characteristics of tsunami-induced atmospheric waves, GUARDIAN can also estimate wave parameters, contributing to improved hazard assessment.
Using the Atmosphere to Monitor the Ocean
Tsunamis disturb the ocean surface, displacing large volumes of air and sending low-frequency gravity and sound waves upward into the atmosphere. These waves interact with the charged particles in the ionosphere, slightly altering the path of GNSS signals. Unlike conventional GNSS software, which treats such distortions as errors, GUARDIAN treats them as clues, using them to identify and characterize tsunami activity.
GUARDIAN is the only publicly available platform offering real-time, multi-GNSS TEC time series across the Pacific. It provides valuable data to scientists, emergency response teams, and decision-makers working to protect vulnerable coastal communities.
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Filling the Gaps in Existing Warning Systems
When an earthquake occurs under the sea, it is a major challenge to determine whether it has triggered a tsunami. Current systems rely heavily on seismic data and deep-ocean pressure sensors, which are highly accurate but expensive and sparsely distributed.
GUARDIAN complements these systems by offering a space-based monitoring solution that provides an additional layer of data. By tracking changes in the atmosphere instead of the ocean floor, GUARDIAN helps confirm whether a tsunami has actually occurred—and does so quickly enough to support time-sensitive evacuation efforts.
GUARDIAN draws on data from over 350 continuously operating GNSS ground stations around the world. Under ideal conditions, it can detect tsunami-related ionospheric signals up to 1,200 kilometers (745 miles) from a station, potentially offering warning times of up to 80 minutes for communities near those sites. This lead time can be crucial in enabling evacuation and disaster response planning.
Because the system doesn’t require knowledge of the tsunami’s cause, whether an earthquake, volcanic eruption, or landslide, it can respond rapidly to a wide range of natural hazards.
Its capabilities are supported by NASA’s Space Geodesy Project and key infrastructure like the Global GNSS Network and the Global Differential GPS Network, which provide real-time geodetic data for monitoring Earth’s dynamic systems.
A New Era in Tsunami Forecasting
The Kamchatka event proved a timely stress test for GUARDIAN. When the earthquake struck, GUARDIAN detected the resulting atmospheric disturbances and issued an early alert.
Unlike conventional systems, GUARDIAN doesn’t rely on assumptions about the event's origin. Instead, it focuses directly on detecting the tsunami’s signature in the atmosphere, a capability that could help reduce the time it takes to confirm a threat and trigger evacuations.
By offering open access to real-time data, GUARDIAN strengthens global tsunami early warning capabilities and supports international cooperation, essential as natural disasters are rarely confined to border lines.
References
- NASA’s GUARDIAN Tsunami Detection Tech Catches Wave in Real Time [Online] Available at https://www.nasa.gov/earth/natural-disasters/tsunamis/nasas-guardian-tsunami-detection-tech-catches-wave-in-real-time/ (Accessed on 25 September 2025)
- Global Navigation Satellite Systems (GNSS) [Online] Available at https://www.unoosa.org/oosa/en/ourwork/psa/gnss/gnss.html (Accessed on 25 September 2025)
- Krishnamoorthy, S. et al. (2023) The GUARDIAN system-a GNSS upper atmospheric real-time disaster information and alert network. GPS Solutions, 27, 32. DOI: 10.1007/s10291-022-01365-6, https://link.springer.com/article/10.1007/s10291-022-01365-6
- SGP: Space Geodesy Project [Online] Available at https://space-geodesy.nasa.gov/about/projOverview.html (Accessed on 25 September 2025)
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