PNT Resilience Against GNSS Signal Interference and Spoofing
The continuous availability of positioning, navigation and timing (PNT) services constitutes a first-order operational requirement for critical infrastructures, civil aviation, maritime transport and governmental applications. GNSS signals, by virtue of their transmission from medium orbit with very low received power levels at the surface, present a structural vulnerability to intentional interference. Jamming, understood as the emission of radio-frequency signals intended to saturate or degrade reception, and spoofing, which consists in the generation of false signals that impersonate legitimate ones in order to induce erroneous position solutions, represent the two principal categories of active threat against these systems. From a mitigation perspective, integrity monitoring constitutes the first level of operational response. Receivers with the capability to detect anomalies in the received signal, such as abnormal variations in the signal-to-noise ratio or inconsistencies in navigation parameters, allow compromised signal conditions to be identified before the PNT solution degrades silently. Signal authentication, a mechanism that enables the receiver to verify the legitimate origin of navigation data by means of cryptographic techniques, adds a layer of protection against spoofing. Galileo incorporates signal authentication capabilities in its open access service, which represents a functionally relevant advancement for applications requiring guarantees of positional integrity. Constelation diversity and diversity of PNT sources is another resilience measure widely adopted in critical operating environments. The simultaneous use of multiple GNSS constellations reduces the probability that a disturbance will simultaneously affect all available measurement sources. Complementarily, the integration of inertial navigation systems allows the continuity of the PNT solution to be maintained during periods of degradation or absence of satellite signal, with an accumulated drift that depends on the quality of the inertial sensors employed. This sensor-fusion architecture is common in aeronautical, naval and land platforms for governmental use. The European regulatory context is paying increasing attention to PNT resilience as a design requirement in critical infrastructures. Bodies such as the European Union Agency for the Space Programme (EUSPA) and the European Union Aviation Safety Agency (EASA) have incorporated considerations of GNSS integrity threats into their regulatory and certification frameworks. For system operators and integrators, the design of resilient PNT architectures entails a systematic assessment of failure modes, the selection of receivers with detection capabilities appropriate to the operating environment, and the definition of contingency procedures that guarantee service continuity in scenarios involving compromised signals.
NASSAT - Network Satellite Systems