Persistent GNSS loss-of-lock from Swarm mission during high solar activity and regional interference: when space science meets geopolitics

Abstract High solar activity can significantly impact Global Navigation Satellite Systems (GNSS) signals, leading to loss-of-lock (LoL) events in satellite-based receivers. A LoL occurs when a GNSS receiver can no longer maintain signal tracking from a satellite, resulting in degraded positioning accuracy. Here, we analyze LoL occurrence using observations from the European Space Agency Swarm satellite mission spanning 2014 to 2025. While LoL events generally correlate with solar activity, reflecting increased intensity of processes driving ionospheric irregularities during active periods, since 2023 a subset of events over Europe and western Asia has been identified that cannot be explained by ionospheric irregularities. These unexplained events coincide spatially and temporally with regions and periods where independent reports document widespread GNSS interference linked to military operations. This study highlights the capability of scientific satellite constellations to detect and characterize GNSS interference, with benefits for space weather research, technological resilience, and situational awareness in conflict regions.