European dependence on satellite navigation has never been greater: from the safe landing of emergency helicopters and precise sowing in fields, to guiding trucks through city traffic jams and synchronizing banking networks that depend on an accurate time reference. At the same moment that the technology of global satellite navigation systems (GNSS) became the invisible infrastructure of modern life, its vulnerability came to the fore. Intentional and unintentional interference, from simple jamming to sophisticated signal spoofing, is today a daily occurrence. It is in this reality that the need for Europe to practically test the resilience of its systems is born – which is exactly the goal of the international Jammertest, in which the European Space Agency (ESA) participates to strengthen navigation resilience in Europe.

Why GNSS is a critical infrastructure that must not stop

GNSS – with the European Galileo system and the American GPS as the best-known representatives – provides two key services: positioning and timing. Positioning enables movement and tracking in space, while the time reference synchronizes systems that simply do not function without precise time. Operators of electricity networks, telecommunication systems, fintech and traditional banks, railways, maritime and air traffic, rescue services and emergency medicine – these are all sectors for which the loss or distortion of a signal can cause a chain disruption. Economists translate such interruptions into direct costs: every hour of downtime multiplies through thousands of nodes of the economy, while security experts warn that the real risk is wider – affecting public safety, logistics chains and citizens' trust in infrastructure that we take for granted.

Intentional interference: from "jamming" to signal spoofing

The dictionary of threats today includes several terms that need to be clearly distinguished. Jamming is the deliberate "jamming" of the receiver: a sufficiently strong interference signal is introduced into the environment that overwhelms sensitive GNSS receivers and prevents them from "hearing" the real satellite signals. The result is a black screen: navigation applications stop giving a reliable position, and devices that we habitually consider banal – from smart watches to in-vehicle systems – are left without references.

A much more dangerous scenario is spoofing, i.e. falsification. The attacker broadcasts convincing, but fabricated, navigation signals that lead the receiver on the wrong path. Unlike jamming, where the user usually immediately notices that "nothing is working," with spoofing the system continues to function, but with wrong data: the map moves, the time slowly diverges, the plane "thinks" it is in another place, and the operator may not notice it immediately. Meaconing is a special variant: the attacker intercepts authentic satellite messages, holds them, and re-broadcasts them with a time shift. Since the messages are real, detection is more difficult, and the deception is more convincing.

Why spoofing is more insidious than jamming

In practice, pilots, dispatchers, and engineers describe spoofing as a "silent" threat: the error does not appear as a malfunction but as a semblance of normal operation. For example, an emergency medical helicopter in flight may get the impression that it is several hundred meters laterally from the actual route; the autopilot – depending on the implemented protections – may try to compensate without the crew recognizing it at first glance. With jamming, on the contrary, alarms appear quickly because the system is left without input. For this reason, today's resilience methods deal with both at the same time: detecting that there is not enough signal and checking that the signal that "exists" really comes from the sky, and not from a hidden antenna on the ground.

How resilience is built: from satellites to receivers

Resilience is not a single layer. At the satellite system level, multi-frequency and broadband services are introduced to allow receivers to compare multiple independent references. The authentication of the navigation message is the purpose of special features to which digital traces are added to the messages to help detect manipulations. For users with approved authorizations, restrictive services are also provided, which are cryptographically protected and more robust in attack conditions. In parallel, ground infrastructure for augmentation – such as systems that enhance the integrity and accuracy of messages – adds additional protection, especially in demanding domains such as civil aviation.

On the receiver side, resilience is built with smart antennas, algorithms that measure the "health" of the signal, comparison with inertial sensors, cartography, and other independent sources such as mobile network signaling. Logic that recognizes unusual behavior is also built-in: a sudden change in signal flight time, "mirroring" from multiple directions, or inconsistencies between frequencies. When there is a suspicion, the system can switch to a degraded mode of operation, retain the last reliable information, or seek help from auxiliary data sources.

Why the laboratory is not enough

Laboratory tests are necessary, but the real world is chaotic: multiple sources of interference, reflections from buildings and terrain, meteorological influences, unexpected bursts in the radio frequency spectrum. Therefore, field tests are crucial to capture what cannot be predicted in the laboratory. This is exactly the logic behind Jammertest – the largest open test environment where industry, academia and the public sector together check the limits of GNSS resilience.

Jammertest as a unique "test polygon" for the entire GNSS chain

Once a year, engineers, pilots, researchers, regulators, and manufacturers gather in the north of Norway to, under controlled conditions and with the coordination of the competent authorities, carry out a complete spectrum of tests: from handheld jammers to multiple sources that work in sync from multiple locations. The testing includes vehicles, unmanned aerial vehicles, airplanes, helicopters, and ships, as well as fixed stations. Participants want to encounter the worst-case scenarios before they happen in real traffic. The idea is simple, but demanding: every receiver or system must "fall to its knees" at least once so that the teams can see where the limits are and what needs to be improved.

Why Bleik on the island of Andøya in particular

The geography of Andøya favors the safe execution of trials: on the one hand, high mountains act as natural barriers that limit the spread of interference towards populated areas; on the other, the open sea allows tests that extend over maritime routes without affecting the wider environment. The small town of Bleik, located about 300 kilometers inside the Arctic Circle and almost on the 70th parallel, thus becomes a temporary outdoor laboratory. During the Jammertest period, the local community is informed in advance about possible short-term disruptions in GNSS services, and the tests are planned to avoid negative effects on the daily life of residents and critical services.

What exactly is being tested: a catalog of scenarios

The organizers prepare a catalog of tests that start from the simplest, to the most complex scenarios. The former includes short-term and local jamming (handheld jammers) aimed at small zones. This is followed by combinations with multiple sources of interference, different powers and modulations, and even coordinated attacks from multiple locations – including from mountain peaks – in which a realistic, changeable environment is simulated. A separate category is spoofing and meaconing, where it is checked whether the receivers can recognize that the message is inauthentic or delayed and, even more importantly, how the system behaves after it realizes this: does it log the incident, does it return to stable operation, does it activate auxiliary sensors and does it report to dispatchers that the data has been compromised.

A "tape" through the entire GNSS supply chain

Jammertest brings together the entire value chain: from chip and antenna manufacturers, through teams that develop algorithms for filtering and anomaly detection, to companies that embed these components in products and integrators that build complete solutions for airplanes, ships, trains, cars, or infrastructure. For all of them, the common polygon means the same thing: truths from the field that cannot be "ironed out" in the laboratory. When the receiver sees an inconsistency between several frequencies, when the antenna "hears" a signal from an impossible direction, when the inertial meters confirm that the vehicle has not moved after all – at that moment the recorded data becomes worth its weight in gold for further refinements.

ESA's role: to test, compare and accelerate innovation

The European Space Agency participates year after year with several missions. First, the resilience of the signals provided by EGNOS and Galileo in Europe is tested in different antenna configurations: from mass-market ones, as found in smartphones, to professional and military solutions with directional characteristics. Second, new receivers and algorithms developed by partners through ESA's innovation programs are under the magnifying glass: they are compared with reference technologies to see how much they have progressed in real conditions. Third, the effect of augmentation systems and message authentication methods is checked in scenarios with multi-frequency, multi-constellation reception, with an emphasis on recovery after an attack.

The special value of field trials is the amount of data. During the campaign, a huge database of raw measurements is collected – from radio frequency records and current positions to sensor telemetry – which is later reproduced in the laboratory. This enables industry and researchers to simulate the same conditions and test new versions of antennas, firmware and algorithms on real-world data, without the need to organize an expensive and logistically demanding field mission every time.

EGNOS and Galileo: resilience built into the design

European systems are properly strengthened at several levels. The first generation of Galileo is already oriented towards resilience through multi-frequency services, expanded bandwidths and mechanisms that help receivers recognize manipulations. In addition, there are services intended for authorized users, with cryptographic protections and features that aim for continuity even in a "hostile" radio environment. In parallel, EGNOS as a ground-based augmentation system – in its current and next generation – provides additional information on integrity and improves accuracy, which is especially important for critical operations such as approaches and landings in aviation.

The next generation of Galileo brings greater flexibility and additional possibilities: faster adaptation to new threats, more robust signal planning and advanced methods of message authentication. On the other hand, the development of the new generation of EGNOS ground receivers, which is being developed by the European industry, is focused on increased resilience in interference conditions, with strict compliance with the security requirements of the sectors that use them.

Receiver resilience: how devices "conclude" that something is wrong

Modern receivers combine several strategies. Spatial filtering (e.g. multi-element antennas) allows for the weakening of signals coming from "suspicious" directions. Time coherence compares the expected message arrival time with the one received; if a consistent shift appears – typical for meaconing – an alarm is activated. Spectral analysis looks for unusual modulation "fingerprints" that are not characteristic of a satellite. Cross-checking with inertial navigation systems (INS) and cartography provides reasonable limits: if the INS says the vehicle is stationary, and the GNSS claims it is moving, the receiver can suspect spoofing. Message authentication provides cryptographic proof that the message comes from a genuine source.

Industry and academia: a common task

GNSS resilience is not just a task for satellites and agencies. Chip and receiver manufacturers are implementing increasingly complex detection methods; system integrators combine them with inertial meters, computer vision and high-resolution maps; researchers in laboratories are developing threat models and automated tests that, once they become standard, will more quickly discover weak points. Jammertest is the place where all this intersects: the same scenario is seen by the antenna manufacturer and the helicopter pilot and the regulator who prepares the guidelines. The feedback is direct and fast.

Critical domains: aviation, energy, banking and public safety

In civil aviation, GNSS enables accurate approaches and procedures in unfavorable weather conditions. If jamming occurs, crews switch to alternative procedures, but spoofing is especially dangerous because it does not manifest as a "break" but as a distortion. Power grids need precise time to synchronize converters, relays and protection mechanisms; a sudden error in synchronization can cause chain reactions. In finance, precise time stamps are necessary for transaction reconciliation and resolution; a difference of a few microseconds can have regulatory and business consequences. Rescue services, on land and in the air, need a reliable position and time to coordinate resources. That is why GNSS resilience is not an abstract technological problem, but a question of people's safety.

How operators and crews are prepared

In practice, organizations that depend on GNSS introduce operational protocols: continuous monitoring of signal "health," thresholds and alarms, overlap with alternative sources of position and time, and plans for switching to degraded modes of operation. Helicopter crews, for example, practice recognizing the symptoms of spoofing (unexplained position shift, disagreement between instruments) and learn how to quickly switch to inertial navigation or radio navigation procedures. In monitoring centers, spectrum monitors are set up to detect anomalies as early as possible and localize them. Field tests, such as Jammertest, feed these protocols back with real lessons.

The role of tests in the development of standards

Field campaigns are not isolated from standardization. The results are translated into reports that shape recommendations for manufacturers, certification requirements in sectoral standards and guidelines for operators. For example, after it is confirmed that a certain type of attack passes "under the radar" of conventional filters, the standard can prescribe additional coherence checks or the mandatory implementation of message authentication in devices that target critical domains. In this way, the polygon from the far north of Europe affects the practice of thousands of users across the continent.

Data and laboratories: "turning back time"

One of the greatest values of Jammertest are the terabytes of recorded raw signals and telemetry. When such a data set is re-run in laboratory conditions, engineers can reproduce the same moment of the test campaign and watch how a new version of the algorithm, a new antenna or a new way of connecting with inertial systems behaves. This accelerates development: instead of waiting for the next field season, progress is measured from week to week on data that truly represents reality. In addition, it also allows for transparent comparison between solutions from different manufacturers under the same conditions.

What a day at Jammertest looks like

The morning starts with a briefing: weather conditions, active scenarios, safety rules and windows in which certain zones will be exposed to interference are reviewed. Teams adjust the flight plans of drones and helicopters, vehicle routes and ship directions, to cover as many combinations and directions as possible. During the day, scenarios of increasing complexity are lined up: from short, "surgical" impositions of interference to half-hour, multi-channel episodes involving multiple transmitters. In the meantime, technical teams monitor the logs in real time, mark anomalies and record the exact time stamps of the incident. In the evening, analysis follows: "quick look" reports for quick feedback and a priority list for the next day.

The role of coordination and safety protocols

Such tests require precise coordination of several public bodies and organizers. Safety plans ensure that interference is kept within defined limits, that it does not overlap with critical services and that local residents and stakeholders are informed in a timely manner. Spectrum monitoring has a special role: a network of measuring stations monitors the spread of signals and confirms that everything is proceeding according to plan. This ensures that the tests are useful, while at the same time being considerate of the environment.

When attacks are "silently" successful: the importance of forensics

In spoofing, sometimes several minutes pass before the system suspects that something is wrong. Therefore, forensic analysis is crucial: it is necessary to have records "before, during and after," with precise time stamps, in order to understand what happened, in what order and how the system reacted. Then the nuances are noticed: for example, the filter correctly detected the discrepancy, but the transition to degraded mode was too slow; or the alarms were too "noisy," so the operators ignored the real incident. Jammertest opens up space for such lessons to be learned without consequences for real operations.

From the laboratory to the field and back: the circle of innovation

Innovation in this area happens in a circular path. Researchers in the laboratory devise detection methods, industry implements them in silicon and firmware, integrators build systems, and then all of this goes through a "baptism of fire" at Jammertest. The reports are returned to laboratories and development departments, where they iterate on weak points. The following year, new prototypes come to the same field – only the attacks are more complex, and the criteria are stricter. In this way, by building a "proof in the field" loop, the entire cycle is accelerated.

What resilience means for end users

For hospital operators, fire and police services, for traffic controllers and energy dispatchers, GNSS resilience must be "invisible": systems should go into a safe mode without drama, crews should have clear and practiced procedures, and incidents must leave a trace that enables quick learning. Ideally, the user only finds out later in the report that a spoofing attempt occurred at a certain time and that the system automatically preserved the integrity of the operation.

Examples of good practices resulting from field tests

• Multi-layered reliance: combine GNSS with inertial sensors, high-definition maps and, if necessary, other radio navigation sources, to reduce dependence on one type of signal.


• Continuous monitoring: embed interference detectors and a signal health indicator that work 24/7, with thresholds that are adapted to the specific environment.


• Incident response: define clear steps when a discrepancy is detected – from automatically "freezing" the last reliable solution, to switching to an alternative source, to notifying dispatchers.


• Forensics: it is mandatory to record events with precise time stamps and metadata, so that a causal analysis can be performed later.


• Crew training: regularly practice recognizing the symptoms of spoofing and jamming and performing procedures for a safe transition to other sources.

Synthesis of the Jammertest idea: show weaknesses so that systems can become stronger

The basic philosophy of the event is openness: the tests are prepared, coordinated and conducted with the participation of a number of public institutions, and industrial and academic partners bring the latest equipment and prototypes. The intention is not to "rank winners and losers," but to collectively learn. When the polygon brings together all the links in the chain – from the antenna to the software, from the cockpit to the control room – then the boundaries of resilience move the fastest.

Seen through the eyes of Europe

For Europe, Jammertest means checking its own capabilities: how Galileo and EGNOS hold up in real threats, how much the receivers and algorithms co-financed by the European industry through innovation programs have advanced, and whether the operational communities (aviation, maritime, road traffic, energy, finance) have received the tools they need. Each field campaign adds a new brick to the wall of resilience – not only in hardware and software, but also in the procedures, standards and training of the people who use these systems every day.

What's next for participants after returning from Andøya

After the field part is over, the analysis marathon begins. Teams pull up logs, compare the behavior of different firmware versions, map cases where the algorithm "saw through" an attack at an early stage and those where it woke up too late, and create correction plans. In the following weeks, updates are created that arrive in airplanes, ships, control rooms and configuration bases. The devices that have passed the polygon return to the "civilian" world, but richer for an experience that cannot be simulated on paper.

Wider social impact

GNSS resilience is not an end in itself. It relies on citizens' trust that emergency help will arrive on time, that an airplane will land safely, that the POS device in the store will be synchronized and that the lights will stay on. In a world where interference and falsifications have become more accessible, and dependence on precise positioning and timing is increasing, joint, field, transparent tests represent the best way for technology to stay a step ahead of threats. Jammertest is therefore not just an event in the north of Europe; it is a proving ground where the resilience of the systems on which daily life rests is honed.

Note on this year's timeframe

Since this year's cycle of activities takes place during September, the dates naturally overlap with autumn operations in aviation, maritime and road traffic. The organizers are strengthening communication with local stakeholders and participants so that all affected sectors have a clear picture of when, where and with what intensity individual trials are being conducted. Such transparency facilitates planning and reduces the possibility of surprises.

Questions that determine the next wave of development

From the perspective of engineers and operators, reasonable questions for the next iteration are: how to speed up the detection of meaconing without false alarms? How much to rely on message authentication in mass devices? How quickly to introduce multi-frequency configurations into sectors with a long equipment life cycle (e.g. railways or energy)? How to standardize incident logs so that forensics are comparable between different manufacturers? The answers to these questions will depend on the lessons learned in the field and the integration of those lessons into standards and operational practices.

The role of community and continuous learning

The last, but not the least important, dimension of Jammertest is the community. Partnerships are formed on the spot, experiences are exchanged and joint projects are born. When the lights of the polygon are turned off, communication continues through working groups, test campaigns in laboratories and "best practice" documents that help those who were not on Andøya to nevertheless adopt proven approaches. In this way, the value of the event spills over to the entire GNSS ecosystem – from manufacturers to end users.