The STOIC project will use cutting-edge atmospheric science to improve an old navigation system, overcoming GPS jamming and spoofing attacks.
Research conducted by the University of Colorado Denver and DARPA (Defense Advanced Research Projects Agency) is providing new insights into how light affects Earth’s upper atmosphere. The result could help the US military overcome GPS (global positioning system) attacks that include jamming and spoofing.
Jamming a GPS straightforwardly means preventing a signal from reaching a receiver, while spoofing involves replacing the real signal with a fake one to mislead adversaries. Although GPS signals are the most predominant means of positioning, navigation, and timing for a multitude of systems, they’re notoriously weak and can often be manipulated.
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For example, Forbes cites a 2016 incident where the Russian military installed GPS jammers on 250,000 cell phone towers. In the following year, the US Maritime Administration reported a GPS spoofing attack in the Black Sea, which caused a merchant marine vessel to have a 30-mile error in its position.
Therefore, it’s critical to find accurate alternatives to GPS tracking. DARPA believes that one option is toward Earth’s upper ionosphere to develop Very Low Frequency (VLF) navigation, positioning, and timing.
Earths ionosphere is a radio-reflect part of the atmosphere that’s about 37 mi (60 km) to 620 mi (1,000 km) altitude. It’s radio-reflective, which radio stations once used to bounce signals to distant listeners. The ionosphere is the most effective at night when it rises, and radio signals could be heard from over 1,000 miles away. These changes in altitude also make the lower and upper parts of the ionosphere extremely difficult to measure, which is key to using it to defeat GPS attacks.
DARPA is revisiting a pre-GPS approach to global navigation using VLF waves through its Spatial, Temporal, and Orientation Information in Contested environments (STOIC) program. It uses surface receivers to track the ionosphere.
“These waves have global reach due to reflection from the upper atmosphere,” Mark Golkowski, a University of Colorado Denver electrical engineer and a bioengineer, told Forbes. “To generate, VLF waves require very large and expensive transmitters, so the covert jamming and spoofing threat is not an issue.”
A major challenge is that the lower ionosphere is currently too difficult to measure in real time. But the University of Colorado Denver researchers are using a lightning probe located 40 to 60 miles up from the Earth’s surface, just under the boundary of space, to study the upper ionosphere. By analyzing the electromagnetic waves from lightning, it may be possible to assess the state of the lower part of the ionosphere in real time.
DARPA hopes that this research data will help it improve an old Navy VLF positioning system that used historical environmental data to predict the position of the ionosphere. That system is currently prone to large position estimation errors. But STOIC may be able to significantly reduce those errors using Earth-based VLF receivers in combination with the data to account for real-time ionosphere movements.
However, Dave Tremper, a program manager in DARPA's Strategic Technology Office, explains that “STOIC will not outperform GPS. But the program is attempting to achieve positioning accuracy that is GPS-like.”
Tremper added that the primary application for STOIC positioning will be to support Navy surface ships. Testing is already being conducted in the Atlantic in live operations under operational conditions consistent with those expected in actual deployments.