Abstract:
In a public satellite navigation system test, Norwegian researchers spent about 40 minutes gradually strengthening the fake signal, and finally made the GPS system of a real-flying rescue helicopter "believe" that it was flying towards the Norwegian Sea. At the same time, the satellite navigation trajectory of another small aircraft was also tampered with, showing that the aircraft was making a sharp turn that was impossible to complete in reality.
This experiment was not intended to cause an accident, but to study what would happen to aircraft and other critical infrastructure when global navigation satellite systems are jammed or spoofed.
This test was conducted during the 2024 Jammertest event on the Norwegian island of Andøya. Andøya is located about 300 kilometers north of the Arctic Circle. It is the location where Norway holds large-scale satellite navigation anti-interference tests every year. Engineers, government agencies, and companies that rely on Global Navigation Satellite Systems (GNSS) will participate in this activity to find possible weaknesses in various devices in the face of real threats through artificial signal jamming and spoofing.
During the flight test that day, a Norwegian rescue helicopter and a small aircraft flown by a pilot from the European Aviation Safety Organization Eurocontrol took to the air. Both aircraft actually followed normal routes, but the GNSS information received by ground monitoring equipment told a completely different story. The helicopter seems to be constantly making dense, overlapping turns on the tracking screen, and the small aircraft shows a series of unusually sharp flight trajectories. In reality, these actions are simply impossible to complete in the way shown in the screen.
What caused this phenomenon was not that the aircraft actually changed its route, but that the researchers sent forged signals to the GNSS receiving equipment. GNSS includes satellite navigation systems such as the American GPS, European Galileo, Russian GLONASS, and Chinese Beidou. Its role is not only to tell the device "where you are", but also to provide extremely accurate time information.
This is also the most noteworthy aspect of the Jammertest test. The researchers not only want to verify whether GPS positioning can be spoofed, but also want to understand the impact of interference with satellite navigation signals on modern infrastructure that relies on precise time synchronization.
In the test, Harald Hauglin, chief engineer in charge of time and frequency measurement at the Norwegian Metrology Service, and his team used a gradually increasing method of GPS spoofing. Instead of suddenly covering the normal GPS signal with a very strong fake signal, they gradually increased the strength of the spoofed signal over about 40 minutes, allowing the receiving device to gradually accept the wrong information.
As the fake signal continues to grow, the location of the test location on the map slowly begins to change. The location marker on the screen gradually moved away from the real location, eventually moving all the way to the Norwegian Sea. The whole process is very slow, so the device does not immediately recognize that it has encountered an abnormality, but gradually accepts the wrong location data.
This kind of "chronic deception" is precisely more dangerous than simple GPS signal loss. If the GPS signal suddenly disappears, the system usually recognizes that navigation data is unavailable and switches to an alternate positioning or timing system. But if the receiving device still thinks it is getting a normal, valid satellite signal, it may continue to use erroneous data and further pass this erroneous information to other systems.
The researchers also tested the situation after GNSS timing was spoofed. To see how time changed, they compared a disturbed GNSS-synchronized clock to an undisturbed reference clock connected via fiber optics on the other side of the mountain. With measurements accurate to nanoseconds, they were able to observe how the spoofed GNSS clock gradually drifted away from the true time.
This problem has implications far beyond aviation. Modern communication networks, power systems, transportation systems, financial markets, and numerous industrial facilities all require multiple devices to share highly accurate time. GNSS has long been an important source of unified time reference for these systems.
For example, different devices in the power grid need to be accurately synchronized, communication networks need to coordinate data transmission according to a unified time, and financial systems rely on precise time recording of transactions. As long as the GNSS signal is temporarily interrupted, some systems can still maintain operation relying on local clocks, atomic clocks or other backup facilities, but how long they can persist depends on the quality of the backup system.
The real danger is that GNSS spoofing may not trigger an obvious failure alarm. Unlike a simple "signal loss," a spoofing attack causes the device to continue to receive seemingly normal satellite data, but this data has been quietly modified by the attacker. If incorrect time or location data continues to propagate, it may gradually affect multiple interconnected systems and create a larger synchronization problem.
In recent years, the importance of GNSS interference has increased significantly. As the conflict between Russia and Ukraine continues, satellite navigation interference incidents have increased significantly in parts of Europe. In May 2026, a British Royal Air Force aircraft encountered GPS interference near the Russian border; in September 2025, the Swedish traffic management department stated that satellite navigation interference occurs almost every day in the local area. Experts also warned that in June 2026, Russian satellites emitted interference signals from space to the ground, causing GPS in parts of Europe to be temporarily affected.
The aviation industry is just the most obvious victim of this problem. Once an aircraft has erroneous positioning information, pilots and air traffic controllers can quickly observe anomalies, but for many other infrastructures, manipulation of GNSS signals may not immediately appear as an obvious failure.
The purpose of Jammertest is to find these weak points in advance. Companies and institutions participating in the test will bring actual commercial and industrial equipment, undergo artificial interference and deception in a public environment, and share the results with other participants after the test is completed. This open testing model is different from related experiments conducted by the U.S. military, which are usually under stricter control and have less public test data.
Faced with the increasingly normal trend of GNSS interference, Norway and other countries are rethinking how much redundant systems are needed in critical infrastructure. Fiber optic timing networks and atomic clocks are important backup solutions. Among them, the White Rabbit technology developed by the European Center for Nuclear Research (CERN) can distribute time to different devices through fiber optic networks with an accuracy of less than 1 nanosecond.
However, these technologies cannot completely replace GNSS. Satellite navigation systems provide location, navigation and time services simultaneously, whereas fiber optic networks or atomic clocks often only solve part of the problem. Therefore, researchers believe that the most realistic solution in the future is not to find a single technology that can completely replace GPS, but to establish a redundant system composed of multiple systems.
The real risk demonstrated by this experiment is not that a helicopter's GPS map suddenly displays errors, but that an infrastructure that modern society relies on may gradually accept incorrect information even when "everything appears to be normal." Norwegian researchers spent 40 minutes convincing a helicopter's navigation system that it was flying toward the sea, proving that one of the biggest dangers faced by satellite navigation systems may not be that it loses its signal completely, but that it continues to work and tells everyone the wrong world.
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