U.S. News: Militaries Try Out Alternatives to GPS

 

 

“GRIFFITH, Australia -- At a tiny airport in the Australian countryside last month, a small plane took off carrying a device that could transform how U.S. drones, aircraft and navy ships navigate across future battlefields.

 

The flight carried an instrument that shines lasers at atoms, which behave like compass needles to measure Earth's magnetic field in real time. Readings from the device can be compared to a magnetic-field map, helping a user determine their location -- and offering a backup to satellite navigation like the Global Positioning System, or GPS.

 

For the U.S. and allies, finding new ways to navigate is crucial. In Ukraine, Russia is jamming and spoofing -- blocking and faking signals -- so frequently that satellite navigation isn't dependable. Other potential adversaries, including China and North Korea, possess similar capabilities.

 

GPS spoofing by militaries has become a civilian hazard as well, presenting a risk to commercial aircraft.

 

"This problem hasn't been as urgent until right now, when we are seeing the end of reliable GPS," said Russell Anderson, a principal scientist at Q-CTRL, the Australian startup that ran the test flight. "It is the arms race of the current day, in terms of navigation."

 

Scientists around the world are exploring whether harnessing the quantum properties of atoms can help navigate accurately in so-called contested environments. But it is still unclear whether the devices, which work well in labs and field tests, would perform reliably on actual military missions.

 

The Pentagon is hoping to solve that problem. In August, the research and development agency at the Defense Department launched a program to help make quantum sensors more robust.

 

The agency said the extraordinary sensitivity of the devices makes them fragile in real-world environments, where vibrations or electromagnetic interference can degrade performance. Australia-based Q-CTRL was selected to participate; another company, Safran Federal Systems in Rochester, N.Y., also said it was awarded a contract.

 

The work is taking on increasing urgency. Russia and China have advanced their electronic-warfare capabilities. European officials have accused Russia of widespread jamming of aircraft.

 

The problem with GPS is the signals are typically weak, making them easy to block. The U.S. has been rolling out a more powerful GPS signal for the military called M-code that is more resilient to jamming, but there has been a holdup in getting funding for the receivers needed to use it, said Todd Harrison, a senior fellow at the American Enterprise Institute.

 

"The U.S. military now realizes future battlefields will be fully contested in the electromagnetic domain unlike anything we have seen before," he said.

 

Quantum devices, potentially working together, could tip the balance, proponents say. Quantum clocks, for example, could boost the precision and accuracy of timekeeping. Another quantum sensor, also being developed by Q-CTRL, can navigate by detecting small changes in gravity.

 

"Quantum sensing is a priority," said Tanya Monro, the chief scientist for Australia's Department of Defence, which hosted a trial of the Q-CTRL gravity sensor on one ship. "There is an absolute, driving need to be able to operate with complete denial of GPS."

 

The Q-CTRL device on the plane in Griffith is called an optically pumped magnetometer. It shoots lasers at atoms of rubidium, a soft, silvery-white metal, that are held in a gaseous form in a small glass vial. The lasers help measure changes in the atoms' internal compass needle, which is used to calculate the strength of the magnetic field.

 

Q-CTRL's software then removes interference from outside sources, such as the aircraft itself, producing an accurate measurement of the Earth's magnetic field in that location, which can be compared to a magnetic map. Such maps show deviations from the average field strength over the surface of the Earth.

 

"You can go out in the woods, and with a map and your eyes identify, 'Well, there's a hill and there's a valley and there's a stream, so I think I'm right here on the map,' " said Michael J. Biercuk, the American quantum physicist who founded Q-CTRL. "You can do exactly the same thing with these magnetic signals."

 

Biercuk said there is no realistic way to jam quantum magnetometers or gravimeters from a distance, short of an energy pulse that would fry all the electronics on a plane and cause it to crash. He said Q-CTRL has subjected the sensors to shaking and dynamic maneuvers with good results -- including more than 140 hours of continuous operation on the Australian ship.

 

In Griffith, Q-CTRL engineers tested three magnetometers in different locations on the plane, given that the external interference in each spot is different. The units were tested against a high-end inertial navigation system [1] -- which estimates position by using gyroscopes and accelerometers. These systems are already used as GPS backups and on submarines, which can't access GPS when underwater.

 

All three locations performed comparably, Biercuk said. Over an 80-mile test window, a sensor on the tip of the plane's wing resulted in an average position estimate within about 620 feet of the true position, and the margin of error didn't increase with the duration of the flight, he said. The performance was more than 10 times better than the inertial navigation system.

 

There are challenges with the magnetometer approach. One is the need to have detailed magnetic maps. Another is to make the device inexpensive enough for cheap drones.

 

"Quantum offers a lot of potential," said Allison Kealy, a professor at Swinburne University of Technology in Melbourne. She noted, though, that "I think they're like any other sensor. They have their strengths and weaknesses."

 

In Griffith, not everything went smoothly. At one point, there was a communication issue involving the wingtip sensor, and it was swapped out for a different unit. More work is ahead, some of the Q-CTRL scientists said.

 

"Can it survive a rocket launch? Can it survive a crash landing?" said Yuval Cohen, a Q-CTRL researcher. "You don't really know, until you do the testing."” [2]

 

1. A high-end inertial navigation system (INS) works by using highly accurate sensors like fiber-optic gyroscopes and accelerometers to measure an object's acceleration and rotation, and then a computer calculates its position, velocity, and attitude. Unlike consumer-grade systems, high-end INS use superior hardware and rigorous calibration for much greater accuracy and minimal drift, and often fuse data with external sources like GNSS (GPS, GLONASS, etc.) for the best performance. They can also integrate other sensors, such as magnetometers, to provide additional heading information.

 

Core components and functions

 

    Accelerometers: Measure linear acceleration along three perpendicular axes. A high-end system uses precise, stable accelerometers to accurately detect changes in velocity.

    Gyroscopes: Measure angular velocity (rate of rotation) around the same three axes (pitch, roll, and yaw). High-end systems often use fiber-optic or ring-laser gyros for greater stability and lower drift compared to basic MEMS gyroscopes.

    Magnetometers: Measure the Earth's magnetic field to provide an independent heading reference. They can improve accuracy, especially in systems with low reliance on GNSS, but are sometimes omitted in military-grade systems where magnetic interference is common.

    Computational Unit: A powerful computer processes the raw sensor data in real-time. It integrates the measurements to continuously calculate the system's attitude, velocity, and position relative to a known starting point and orientation.

    Initial Alignment: Before starting, the system performs an alignment process to establish its precise starting position and orientation, determining horizontality and the direction of true north.

 

How the system maintains accuracy

 

    Integration: The computer integrates the accelerometer data to determine velocity and then integrates again to find position, while the gyroscope data corrects for any rotational movement.

    Sensor Fusion: To overcome the inherent drift of INS, high-end systems fuse the INS data with external navigation sources, most commonly GNSS. The INS provides fast, real-time motion data, while the GNSS provides long-term positional accuracy to correct the INS.

    Advanced Calibration: High-end units undergo extensive calibration processes, often temperature-based, to ensure the highest possible accuracy across the full operating temperature range.

    Hardware Isolation: Sophisticated designs use both passive and active systems to isolate the sensors from vibration, shock, and rotation, which minimizes errors and interference.

 

The cost of a Chinese inertial navigation system (INS) varies widely depending on its components, performance, and application, with prices ranging from approximately $550 USD for basic modules to over $100,000 USD for high-precision, aviation-grade systems.

 

2. U.S. News: Militaries Try Out Alternatives to GPS. Cherney, Mike.  Wall Street Journal, Eastern edition; New York, N.Y.. 20 Nov 2025: A4.