GNSS Interference Does Not Only Come From the Ground: What Recent Observations Mean for Resilient Navigation
When we talk about GNSS jamming, we often have a familiar scenario in mind: a jammer located on the ground or inside a vehicle overwhelms the weak signals transmitted by GPS, Galileo and other satellite navigation systems.
A recent observation by our partner GPSPATRON shows why this picture may be too narrow. In September 2026, a network of independent GNSS monitoring stations across Europe detected an unusual interference event affecting GPS and Galileo frequencies almost simultaneously. Analysis indicates that the interfering transmission originated in space.
That is unusual. But when considering how a GNSS receiver can deal with interference, the geographical origin of the signal is only one part of the problem.
What was observed?
On 3 September 2026 at approximately 09:10 UTC, GPSPATRON's European monitoring network detected a short degradation in GNSS reception at geographically separated monitoring locations almost simultaneously.
Both GPS and Galileo were affected. Depending on location and receiver, the observed carrier-to-noise ratio (C/N₀) decreased by approximately 2 to 5 dB-Hz.
The event was observed using different types of monitoring equipment, including RTK stations, Septentrio receivers and dedicated GNSS interference sensors. Raw RF data were also recorded.
GPSPATRON identified a transmission centred at approximately 1577.5 MHz with a bandwidth of around 2.46 MHz. Based on the wide geographical area affected, the timing of the observations and other signal characteristics, their analysis concludes that the transmission was space-based.
There is, however, an important distinction between interference and intentional jamming.
A transmission that affects GNSS reception was not necessarily generated for that purpose. GPSPATRON explicitly notes that the origin or intended function of the observed signal has not yet been conclusively determined. Possible explanations include another satellite function, a test transmission or unintended in-band emissions.
Why the direction of interference is not the whole story
GNSS signals arrive at the Earth's surface at extremely low power levels. Additional radio-frequency signals within or close to the frequencies used by GNSS can therefore affect reception.
From the receiver's perspective, the first question is what signal arrives at its antenna.
Relevant parameters include:
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frequency and bandwidth
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interference power relative to the GNSS signals
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temporal behaviour
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modulation and signal structure
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affected GNSS bands
Whether the source is located on the ground, on an airborne platform or in space does not fundamentally change this situation.
That does not mean direction is irrelevant.
Spatial anti-jam techniques such as Controlled Reception Pattern Antennas (CRPA), beamforming and null steering depend strongly on the direction of arrival. These systems can reduce signals arriving from particular directions.
Receiver-level techniques take a different approach. They analyse and process the received signal itself and can detect and suppress certain types of interference, for example in the frequency or time domain.
The two approaches are complementary, but they address different parts of the problem.
What Jammertest 2026 tells us
At around the same time as the GPSPATRON observation, GNSS receivers and PNT systems were being exposed to controlled real-world jamming and spoofing scenarios during Jammertest 2026 on Andøya, Norway.
Septentrio subsequently published initial results from tests of its AIM+ interference mitigation technology. Among other scenarios, receivers were exposed to strong chirp interference. The published results indicate that modern receiver signal processing can significantly reduce the impact of certain interference signals and improve the availability of the GNSS solution.
Spoofing – the transmission of manipulated GNSS-like signals intended to produce an incorrect navigation solution – was also part of the testing.
These results are relevant to resilient navigation, but they should not be overinterpreted. Successful performance against a particular jammer does not demonstrate immunity against every possible interference scenario.
In particular, the space-based signal observed by GPSPATRON was not reproduced during Jammertest.
The connection between the two developments is therefore technical rather than experimental: they illustrate different aspects of the same problem.
Detection and mitigation are different tasks
The two recent developments also highlight an important distinction.
Interference detection addresses questions such as:
Is the GNSS spectrum being disturbed? Which frequencies are affected? How strong is the interference? Could it be jamming or spoofing? When and where is it occurring?
Interference mitigation, on the other hand, attempts to reduce the effect of an existing disturbance on the navigation solution.
A system can detect interference very effectively and still lose its GNSS position. Conversely, a receiver may successfully suppress certain interference without providing the operator with a complete picture of what is happening in the surrounding RF environment.
For safety-critical and autonomous systems, both capabilities therefore matter.
Resilient PNT is more than a robust GNSS receiver
These observations illustrate why resilient positioning, navigation and timing (PNT) should be considered at system level.
A modern GNSS receiver with interference mitigation provides an important line of defence. It can increase the probability that GNSS remains usable in difficult RF conditions.
But it cannot guarantee that GNSS will remain available or trustworthy under every circumstance.
Resilient PNT architectures therefore combine several layers:
Detect → Mitigate → Assess Integrity → Continue Navigation
Interference is detected and characterised. The GNSS receiver attempts to reduce its effects. At the same time, the system needs to determine whether the resulting position can still be trusted. If GNSS is no longer sufficiently available or reliable, additional sensors or navigation sources must support or temporarily replace it.
For autonomous vehicles, UAVs and other unmanned systems, this last point is particularly important. An autonomous system does not merely need to calculate a position. It also needs to know when that position should no longer be trusted.
From interference source to system resilience
The observation of space-based GNSS interference therefore primarily broadens the way we should think about the problem.
GNSS interference does not have to resemble the traditional scenario of a ground-based jammer. It can have different causes, signal characteristics and directions of arrival – and it does not even need to be intentionally directed at GNSS to affect its availability.
For the design of resilient navigation systems, this leads to a simple but important conclusion:
Preparing for only one type or one origin of interference is not enough.
Robust systems require a combination of GNSS and RF monitoring, receiver-level interference mitigation, integrity assessment and additional navigation sources.
The key question is therefore not only:
Where does the interference come from?
It is also:
Can the system detect it, limit its impact and continue to determine where it is – while knowing how much that information can still be trusted?
Sources and further reading
Contact:
https://www.hensec.com/en/component/content/article/regina-air-3?catid=22
https://www.hensec.com/en/products/gps/gps-spoofing-and-jamming-detection
https://gpspatron.com/satellite-gps-galileo-interference-europe/
https://www.jammertest.no/jammertest-2026/