NASA satellites designed to observe cyclonic wind speeds and collapsing ice sheets have also proven capable of identifying the approximate locations of GPS jammers. This could help monitor high-risk areas for aircraft and ships given the increasing prevalence of GPS interference around the world.
Two different NASA satellite systems showed how they can detect a known but mysterious GPS jammer within several kilometers of its position in Iran, according to an experiment by Shawn Gorman, CEO and co-founder of location-based technology company Zephr.xyz, which is detailed in GPS World magazine. Such jammers use stronger signals to overcome weaker radio signals coming from US-operated GPS satellites and other global navigation satellite systems.
Clara Chew, principal scientist and head of the GNSS systems and data team at California-based satellite maker Muon Space, who was not involved in the study, said such NASA satellites cannot provide “near real-time monitoring” or pinpoint the exact location of a GPS jammer. But Chew told Ars that identifying the approximate locations of GPS jammers “could potentially be helpful for flight planning” or “to indicate high-risk areas for maritime shipping.”
One of the NASA satellite systems, the Cyclone Global Navigation Satellite System (CYGNSS), consists of eight microsatellites that detect GPS signals reflected from ocean surfaces to measure wind speeds within the eyes of hurricanes, tropical cyclones, and typhoons. When an Earth-based jammer is triggered, the effect creates a huge footprint in reflected GPS signals that can be visible hundreds of kilometers away from the jammer’s location.
The other satellite system, the NASA-ISRO Synthetic Aperture Radar (NISAR), typically uses radar imaging to continuously map and track changes on the Earth’s surface, including earthquakes, tsunamis, volcanoes, and ice sheet collapse. GPS jammer emissions create streaks in NISAR radar imagery that run perpendicular to the direction of flight — meaning that “each streak encodes the jammer’s direction relative to the satellite’s ground track,” Gorman writes in his GPS World article.
“CYGNSS looks at the effect of jammers on reflected GPS signals, offering indirect measurements spanning hundreds of specular reflection points,” Gorman wrote. “NISAR looks at the jammer’s emissions directly into its receiver, which is a more accurate measurement, but only along the satellite’s narrow ground track.”
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