A SpaceX Falcon 9 launched a GPS 3 satellite from Space Launch Complex 40 at Cape Canaveral Space Force Station, Florida, June 17, 2021. Credit: U.S. Space Force

For decades, the Global Positioning System (GPS) constellation has reigned supreme as the world’s go-to navigation tool — guiding everything from aircraft carriers to Uber drivers.

But GPS is susceptible to jamming and spoofing. Malicious actors can deliberately disrupt or manipulate the signals, leading to inaccurate or misleading positioning information.

These vulnerabilities endanger critical infrastructure, emergency response and military operations, prompting increased interest in alternative PNT, or positioning, navigation and timing technologies that do not depend on GPS.

While the Pentagon has long pursued augmented GPS capabilities, including using allied backup systems, it is now scoping a burgeoning commercial market promising innovative options to reduce GPS dependence.

In response to the military’s call for PNT alternatives, companies are lining up with offerings to fill gaps if GPS ever goes dark. These range from terrestrial networks that leverage existing cellular infrastructure to new constellations of low-orbiting small satellites broadcasting PNT signals.

Global reliance on GPS

The Global Positioning System was conceived in 1973 out of a Pentagon effort to develop precision navigation and timing for military operations. But over the decades, this once-obscure space technology spilled over into civilian applications, becoming integral infrastructure enabling the modern global economy.

After the first test satellite launched in 1978, GPS crept into broader usage across land, sea and air forces, enabling precision guidance of military systems. The accuracy of the signals available to civilian users were deliberately degraded.

A U.S. Space Force guardian conducts GPS electromagnetic interference training at Schriever Space Force Base, Colorado. Credit: U.S. Space Force photo by Ethan Johnson

After the Soviet Union collapsed in 1991, GPS was increasingly opened for mass use. In 2000, degradation was ended entirely, unleashing GPS’s full economic and social potential. In the wake of its massive success, other nations started building their own satellite navigation systems, including Russia’s Glonass, Europe’s Galileo, China’s Beidou, Japan’s QZSS and India’s IRNSS.

The GPS constellation is now operated by Space Delta 8, a component of the U.S. Space Force headquartered at Schriever Space Force Base, Colorado.

Jammers as “asymmetric” weapons

Russia’s 2022 invasion of Ukraine provided a stark warning of GPS vulnerabilities as Russian electronic warfare systems repeatedly jammed and spoofed critical infrastructure. The Pentagon fears GPS disruptions could become a common tactic, and is especially concerned that China could paralyze the U.S. military in a Taiwan clash by denying access to GPS and other space assets.

“The real concern with electronic warfare are GPS jammers,” Chief Master Sgt. Ronald Lerch, senior enlisted leader at the Space Systems Command’s intelligence directorate, said Jan. 30 at the Space Mobility Conference in Orlando, Florida.

If GPS is disrupted even temporarily, it could cripple operations, Lerch said. “For those who aren’t aware, jammers are no longer these really big vehicle truck mounted systems that are visible from intelligence satellites. GPS jammers can get shoved into a backpack.”

GPS spoofing has been used to disrupt naval operations, for example, to steer commercial vessels into the shipping lanes of U.S. Navy battle groups. Low-cost jammers can also be placed on floating sea buoys that anonymously disrupt from random locations.

DoD views GPS jammers as an asymmetric weapon because they are relatively inexpensive and accessible devices that have outsized impact, given the U.S. military’s heavy reliance on GPS.

“These asymmetric capabilities are going to be something that we have to be very careful about,” Lerch said. “And we absolutely cannot lose sight that those capabilities are already out there. Everyone knows the havoc they’ve wreaked in Ukraine.”

Demand for alternatives growing

With so much at stake, the Pentagon has moved to add security features to GPS over the past decade, including a stronger signal called M-code, short for military code, that is more jam-resistant than civilian signals. M-code is available in the newer GPS satellites but most U.S. military forces can’t take advantage of it because M-code capable receivers are not widely available.

As a fallback option when GPS is denied, some military platforms are able to use onboard sensors to track their position and keep time without the use of an external signal. Military combat aircraft use GPS paired with inertial navigation systems so if GPS goes out, the pilot can still complete the mission. Other PNT backups determine position using celestial navigation or terrain referenced navigation, which uses a digital map of the surrounding terrain to match a vehicle’s movement and update its position.

Meanwhile, the private sector saw a need and started developing GPS alternatives.

Satelles in 2016 was one of the first space-based PNT services that didn’t rely on GPS. The company broadcasts timing and location signals through a channel on Iridium Next communications satellites that was previously used for paging.

With the risks to GPS mounting, the Space Force is now looking to harness a new wave of commercial innovations through the Space Systems Command’s new Commercial Space Office (COMSO), created to identify promising technologies and coordinate their adoption.

Space Force initiatives

Working with COMSO, the Defense Information Systems Agency last year invited vendors to compete for the so-called PLEO contract — short for Proliferated Low Earth Orbit Satellite-Based Services. This is a new procurement vehicle aimed at commercial satellite services that provide high-speed broadband and Earth imaging, but also alternative PNT solutions.

The 2nd Space Operations Squadron on Dec. 9, 2023, displayed a graphic identifying the 30th Anniversary of the unit being designated to oversee the Global Positioning Satellite constellation at Schriever Space Force Base, Colorado. M-code is a more powerful, jam-resistant GPS signal. Credit: U.S. Navy photo by Joe Bullinger

Separately, the Space Force’s innovation arm, SpaceWERX, recently launched a program called AltPNT seeking proposals for improving PNT resilience. This summer, it plans to award as many as 20 Small Business Innovation Research contracts to prototype and demonstrate PNT technologies.

COMSO director Col. Richard Kniseley said his office last summer hosted a conference focused on alternative PNT technologies. Following that meeting, “the response and interest from industry has been exceptional,” Kniseley said.

He said COMSO and SpaceWERX are reaching out to the private sector via workshops, industry meetings, webinars and other events.

The SpaceWERX project on alternative PNT, he said, “will provide critical R&D seed funding for capabilities to eventually be procured through COMSO or other government agencies.”

Gen. Michael Guetlein, vice chief of space operations of the U.S. Space Force, said significant effort is going into market research to identify PNT technologies that could be integrated into military systems.

“We really are exploring the entire gamut of alternatives,” Guetlein said Jan. 19 at the Center for Strategic and International Studies in Washington, D.C.

“We’re looking at PNT in space, from the ground and PNT from other data sources, with the objective of making sure we guarantee that the nation will have exquisite positioning, navigation and timing.”

“GPS today drives our entire economy and drives our entire international financial markets,” Guetlein added. “We want to make sure that if that signal ever becomes attacked, or something nefarious happens, that we have alternative ways to get that PNT signal.”

While Pentagon leaders increasingly recognize the necessity of PNT options, practical hurdles lie in implementation. The SpaceWERX program, for example, will look at the challenges of integrating commercial PNT services with military vehicles and weapons platforms built over decades assuming GPS availability.

“The biggest constraint that I see is how do we integrate with user equipment, and how do we bring capability to the ground segment as well,” said Lt. Col. Justin Deifel, head of the U.S. Space Force Futures Branch.

Commercial PNT solutions

Commercial PNT players insist that they can’t replace GPS, but are responding to U.S. government and commercial demand for backup or complementary technologies that makes them less dependent on a single system.

Xona Space Systems, based in California, is developing a PNT service designed for self-driving cars and drones that’s also aimed at the defense market.

“We’ve seen the demand growing in a lot of different market segments,” said the company’s co-founder and chief executive officer Brian Manning.

Xona in 2025 plans to start building a constellation of between 250 and 300 small satellites in low Earth orbit. The company worked with the Air Force under SBIR contracts, and counts Lockheed Martin Ventures as one of its investors.

Manning said new space-based PNT services in low orbits provide higher accuracy. The signals only have to travel a few hundred miles, compared to GPS which broadcasts from satellites about 12,000 miles above Earth.

Xona does not plan to make user devices, and instead is partnering with existing GPS equipment companies to integrate the company’s software in their receivers.

“The GPS community has realized that often the most expensive and challenging part about deploying a new service isn’t the infrastructure. It’s not the satellites. It’s actually the user equipment,” Manning said. “You’ve really got to be able to integrate with existing user equipment, and that’s something that we’ve seen the military have a very strong appetite for.”

Some of Xona’s partners have already built prototype receivers to show that they can pick up and use our signals, Manning said.

The defense market is now becoming attractive because the government has “started to really figure out how to work with commercial companies, especially in recent years,” he added. “They’re taking that approach with satellite communications with systems like Starlink.”

“What we’re bringing to the table is that same approach but in the navigation role, where historically there just really hasn’t been much investment,” Manning said.

DoD seems ready to really start adopting alternatives to GPS, he said. “You have a single point of failure, which is kind of where we are today with GPS. It’s so ingrained in everything.”

Another startup poised to compete in the alternative PNT market is Virginia-based TrustPoint Inc., which so far has launched two demonstration satellites and is moving forward with plans to build a LEO network of about 300 smallsats.

TrustPoint’s co-founder and chief executive Patrick Shannon for years worked in the telecom industry and saw a void in the market for commercial PNT.

“Very few folks were innovating from the commercial side,” he said.

Seeking to fill that demand, Shannon teamed up with Chris DeMay, who previously co-founded the remote sensing startup HawkEye 360.

“We believe GPS has to be something where the commercial world helps out the same way it’s helped out on launch or Earth observation,” DeMay said. “GPS is the next big opportunity for dual-use technology.”

Encryption is a major focus of the TrustPoint service, he explained. “The way we do PNT is very similar to GPS in that we’re broadcasting. Our messages are encrypted. And that encryption is available to not just the military users, but also to civil and commercial users.”

Four GBU-39 small diameter bombs sit in a storage area at Al Udeid Air Base, Qatar. The U.S. Air Force stores the GPS-guided bombs in a war reserve munitions stockpile. Credit: U.S. Air National Guard photo by Staff Sgt. Jordan Martin

There are many military users who don’t have access to GPS encrypted M-code signals because the development and production of user equipment is years behind schedule, he pointed out. “So they’re using commercial GPS receivers that are not encrypted technology, which is a security issue.”

While GPS and other PNT satellite systems transmit their signals in the L band portion of the radio spectrum, TrustPoint moved to the C band.

“There [are] a lot of adversaries that know how to mess with L band,” said Shannon. For DoD users, having access to a different frequency is a “big value proposition that the folks we’ve talked to in the DoD are very interested in.”

Like Xona, TrustPoint is partnering with receiver suppliers, he said. “They would build essentially a next generation device that would also include the TrustPoint capability.”

The company plans to field an initial constellation of between 30 and 50 spacecraft “to get things going,” said Shannon. The full constellation of 300 would be completed by 2028 or 2029.

“Signals of opportunity”

Navsys Corp., based in Colorado, pioneered research of core technologies used as alternatives to GPS, including terrestrial PNT that provides location and timing information without relying on satellites.

The company’s chief executive Alison Brown, who founded Navsys in 1986, has worked with government agencies developing and testing PNT receivers that rely on ground networks, such as Wi-Fi or Bluetooth. The company’s software enables receivers to simulate PNT signals derived from terrestrial networks.

One of Navsys’ key projects was to support the Federal Aviation Administration’s Wide Area Augmentation System (WAAS), which uses commercial communications satellites to improve the accuracy of GPS for aviation use.

“We proved that you can actually use commercial satellites as alternatives for PNT,” Brown said.

Navsys now offers a PNT service that uses “signals of opportunity,” or existing radio signals that can be used for PNT even though they weren’t originally designed for that purpose.

A GPS receiver, to calculate position, needs to simultaneously receive and process signals from at least three different satellites. Alternative PNT using terrestrial and commercial satcom works in a similar way fusing other signals of opportunity, Brown explained.

The sensor-fusion approach for PNT also is being used by Parsons Corp., an intelligence and engineering contractor.

The company in 2021 acquired Virginia-based Echo Ridge, a defense contractor that patented signal processing algorithms for PNT.

“We’ve been investing in this area in anticipation of government needs,” said Mike Kushin, president of Parsons’ defense and intelligence business.

The company’s software integrates terrestrial and LEO satellites’ signals, he said. Parsons also offers a miniaturized jam-resistant receiver designed for airplanes, drones and munitions. “What’s pretty unique about our capabilities is that we focus on moving objects.”

Parsons is partnering with munitions suppliers that would use the company’s software-based PNT device as a backup or augmentation to GPS.

“We know the government has been looking at ways to provide redundancy and resilience against GPS,” Kushin said. “We anticipate that the government is going to be making more investments in this area.”

A missile equipped with Parsons’ receiver would capture GPS signals but, if GPS is jammed, it would continue to navigate using the alternative PNT source.

Parsons is developing proprietary PNT receivers but also plans to license its PNT software for use on existing GPS devices.

The company aims to compete for PNT opportunities under the Space Force’s PLEO contract, said Kushin. “But beyond that, there’s other DoD organizations that are looking to tackle this problem.”

The PNT market is poised for a surge in commercial capability thanks to innovations coming from the space industry, he said. “And the one place that the government has been more than open to using commercial services is the space domain.”

The vulnerabilities of GPS have long been known, Kushin said. But organizations have been slow to embrace alternative technologies, and that appears to be changing, he said. “We are sort of reaching this inflection point.”

Where is the money?

While companies express confidence in the defense market, they have not yet seen interest translate into actual funding.

It is still unclear how much funding the Space Force will seek for alternative PNT, Brown noted. Another concern for suppliers in this sector is that the military’s massive investments in GPS infrastructure, and the operational familiarity, create inertia.

SpaceWERX’s alternative PNT program for small businesses is welcome, she said, but SBIR tends to fall short in helping companies bridge the gap between R&D and commercialization.

“Within the community that offers alternative solutions to GPS, I will say that there is a certain level of frustration in getting the DoD to consider acquiring them, and I have had conversations with the Commercial Space Office about this,” Brown added.

“SBIR is not encouraging, and it doesn’t show real commitment,” she said.

Shannon said the pressure is now on the industry to show customers the capabilities of commercial PNT. He expects DoD will boost funding once these new technologies become “well accepted and verified.”

“The Army has a massive role in PNT because of the quantity of soldiers and platforms that they deploy on the ground,” Shannon said. “And to that extent, they have a heavy hand in deciding what comes next.”

COMSO’s PLEO contract, he noted, now gives the Space Force a potentially important role in identifying relevant technologies.

DeMay observed that the combination of the “demand signal from the warfighter across all branches, combined with the newfound availability of commercial PNT solutions have really led to the opportunities that we’re seeing over the next couple of years.”

This article first appeared in the February 2024 issue of SpaceNews magazine.

Sandra Erwin writes about military space programs, policy, technology and the industry that supports this sector. She has covered the military, the Pentagon, Congress and the defense industry for nearly two decades as editor of NDIA’s National Defense...