In modern military conflict, the Global Positioning System is a prime target.
For the U.S. armed forces, it’s the main source of positioning, navigation and timing. They depend on it not only to find their way but to synchronize their movements and ensure the accuracy of guided weapons.
It’s very good at all those things, which is why adversaries want so badly to take it away. The strategy is this: Jam a GPS signal, or hijack it with false information, and you essentially control the other side’s ability to operate.
Anti-jamming and anti-spoofing capabilities, such as those produced by Raytheon Intelligence & Space, are a common feature of navigation receivers. But there’s more work to do. In the 2021 National Defense Authorization Act, for example, the U.S. Senate Armed Services Committee instructed the Defense Department to ensure more resilient and survivable positioning, navigation and timing capabilities.
In the spirit of the mandate, RI&S is now doing exactly that. The business is developing resilient receivers for alternative navigation through fusing signals and sensors, using advanced techniques like machine learning and employing the Markov decision process, a framework for modeling decision-making where outcomes are partially random and partially under the control of the user.
Sending mixed signals
“We are working to bring to bear all the capabilities across Raytheon Technologies to ensure our customers can complete their mission in any environment, whether that’s GPS-enabled, GPS-contested or GPS-denied,” said Ben Graham, an RI&S director in Resilient Navigation and Reconnaissance Solutions. “For us, signal and sensor fusion is a key enabler for our customers to achieve resilient navigation so they can complete their missions under the most challenging electronic warfare conditions.”
At the core of RI&S’ resilient navigation work is the Application-Specific Integrated Circuit, or ASIC. The ASIC is the key to processing and protecting navigation signals, and it’s only about the size of two quarters stacked on top of each other.
“The minimal size, weight and power of the ASICs allows us to get a lot of processing punch into a handheld, battery-operated device,” Graham said. “This is a capability that used to be in a package the size of shoebox, and now it’s in a device the size of an iPhone that U.S. Army troops can carry in the palms of their hands on the battlefield.”
GPS is the gold standard. It’s reliable and it’s accurate, meaning it’s always the first choice for the U.S. military and many of its allies. But even great technologies need a backup, so RI&S is looking at both alternative signals and sensors to ensure trusted navigation, which can be processed through ASICs.
“For alternative navigation signals, we’re looking at the European Union's Galileo, Japan's Quasi-Zenith Satellite System, new low-Earth orbit systems, and other military and commercial constellations in the works and flying today,” said Jarrett Perry, RI&S program area chief engineer for Resilient Navigation and Reconnaissance Systems. “That’s where algorithms and machine learning come in, determining which signals are accurate and which ones aren’t.”
Timing is everything
Next-generation ASICs will also be handling a lot more information. They will fuse data from various sensors including:
- accelerometers that, well, measure acceleration,
- visual recognition using cameras and radar that can recognize landmarks and terrain,
- magnetic sensors that have been used for centuries in compasses,
- radio frequencies,
- advanced timing, because finding position in the world is impossible without accurate time since the Earth is always rotating.
“If a pilot finds themselves in a GPS-denied environment, then ASIC's using machine learning can sort through and fuse this sensor data autonomously to determine position, navigation and timing,” Perry said.
According to Perry, RI&S plans on having a ground-based prototype for mounted and unmounted soldiers in 2024, and begin fielding units in 2025.
“Our focus is that all of our signals and sensors have unrivaled resiliency – unmatched anti-jam and anti-spoof for signals, and advanced cybersecurity for sensors,” Graham said. “As the often repeated adage says, ‘the best offense is a good defense,’ and Raytheon Intelligence & Space plans on defeating emerging threats in navigation warfare by having the best defense.”