The service is among the CPNT options designed to toughen and augment GNSS—and it’s available globally today.
MICHAEL L. O’CONNOR, Ph.D., became Executive Vice President, Positioning, Navigation, and Timing (PNT) Division when Iridium acquired Satelles. He served as CEO of Satelles since it was founded in 2013 and led the charge to bring the STL service to customers worldwide. Before Satelles, he co-founded IntegriNautics (later renamed Novariant and acquired by AgJunction) and served as chief technical officer, vice president of business development and CEO. He received his BS in avionics from the Massachusetts Institute of Technology (MIT) and his MS and Ph.D. in aeronautics and astronautics from Stanford University.
The rest of the world is starting to see what the PNT community has known for years: We must protect and augment GNSS.
There’s a growing awareness of the threats spoofing and jamming pose to GNSS, and what would happen if the system so many rely on went down. People from outside the industry want complementary solutions designed to enhance GNSS resiliency and protect critical infrastructure, driving the push to create a more layered approach.
The industry is working to develop solutions that help mitigate ever-evolving threats, with manufacturers creating and testing complementary PNT (CPNT) solutions that can backup GNSS. Some, like Iridium Satellite Time and Location (STL), are already making a difference today.
Michael O’Connor co-founded Satelles, the company behind STL, more than a decade ago to address society’s overreliance on GNSS, an impressive, accomplished system but one that is susceptible to degradation, interference and cyberattacks. STL was developed to provide a separate service that’s impervious to the types of attacks GNSS is vulnerable to. Last year, longtime partner Iridium acquired Satelles, with the plan to drive adoption in markets Satelles already had a strong presence in, like the wireless industry and data centers, and to expand the STL service into core Iridium markets like maritime and aviation.
The service, now Iridium STL, was already using Iridium’s cross-linked L-band network before the acquisition, leveraging the strong broadcast paging channels of the Iridium satellite constellation to deliver precise timing information.
STL has been in service since 2016, with the mission to secure PNT-dependent applications—particularly critical infrastructure—against disruption. The service is available globally and is becoming a critical layer for those who must protect PNT.
“After a decade of industry working and trying to solve this critical problem, the world has become aware that it’s a critical problem,” said O’Connor, who is now Iridium’s executive vice president of the PNT division. “Fortunately, the industry is lined up through foresight to solve the problem. Iridium STL is one solution, and there are others.”
While the threat to GNSS and all who rely on it has grown in recent years, “We can take heart in the fact there are alternatives out there, we just need to make sure those alternatives are being adopted to provide the resiliency needed. With layers you do get resilience. There’s no question about it.”
Complementing GNSS
Iridium STL provides an independent signal that is not designed to replace GNSS; rather, it’s designed to complement it, O’Connor said. It can be accessed from the same receivers as GNSS and GPS, making it easy to incorporate as part of a layered approach.
What makes STL different? First, it uses Iridium’s low Earth orbit (LEO)satellite network. GNSS satellites are almost entirely in middle Earth orbit (MEO). That makes STL signals about 25 times closer to the Earth. They’re also 1,000 times stronger. Because of that high power, STL can reach indoors and cut through interference.
“STL has 30 db more ability to penetrate jamming,” O’Connor said. “It takes about 1,000 times more power to fully jam an STL signal, so if you have a jammer the effective radius that jammer can cover is 30 times less.”
Iridium STL has spoofing resilience as well, with a cryptographic key built into the signal. This enables users to validate that the signal received came from a satellite and not from a spoofer, O’Connor said.
“It’s easy to replicate a GPS or GNSS signal,” he said. “It’s extremely difficult to replicate an STL signal because we’ve included cryptography tags in the data from the satellite.”
While Iridium STL is not at the same frequency as GNSS and GPS, it is on L-band, which has its advantages. For example, STL signals don’t suffer from power loss as they travel through the atmosphere, an even bigger problem for other signals if there’s any kind of moisture, O’Connor said. Users also don’t need to invest in the larger antennas required for bands that are at higher frequencies, like Ka and Ku—which is key for mobile users like maritime and defense. And because STL is in the same spectrum as GNSS, it’s an easy add on.
“Users can leverage existing GNSS and GPS antennas,” O’Connor said, “making it a cost effective upgrade.”
A Global Solution for Various Markets
Iridium focuses on markets that “care a lot about resilience,” O’Connor said. For example, there are many fixed station or static timing STL users who leverage the service to protect the critical infrastructure around data centers, telecom, financial markets and stock exchanges. Mobile users who need the precise PNT capabilities STL provides include maritime, aviation and defense. Iridium STL users typically require accuracy in the 10 to 20 meter range, which is sufficient for most GNSS use cases.
Iridium’s cross-linked network makes it possible to deliver a global service to all its users through a limited number of fixed ground stations, O’Connor said. Users don’t need to be located near one to take advantage of it.
“Many users really require a global capability, and that’s Iridium STL,” O’Connor said. “Not all proposed or available systems offer that. And it’s available today.”
Integrating into the GNSS Ecosystem
Any solution designed to improve GNSS resilience must be integrated into the GNSS ecosystem of equipment and service providers. Iridium STL partners with companies that offer GNSS equipment, including VIAVI, Adtran and Safran. Customers can easily purchase an STL upgrade to add that extra layer of resiliency into their solution.
“These are some of the companies known for providing resilient GNSS into the market,” he said. “As partners they offer products with STL options. They can replace a GPS only or GNSS only box with a GNSS Plus STL solution that drops right into place.”
And many of these vendors are finding innovative ways to use Iridium STL, O’Connor said.
“Our partners are taking STL and integrating it into other solutions and different types of oscillators, gyros and other sensors to provide a range of options for users,” he said. “A lot of time, performance enhancements come from our manufacturing customers who are innovating in the market to meet the needs of specific users. We’re always amazed at the innovative spirit of our partners who really understand the needs of the customers they serve and take STL and adapt it in ways that are meaningful.”
A Focus on Adoption
Complementary solutions that make GNSS more resilient exist today, but they can’t do much to help society unless they’re adopted, O’Connor said. That’s where the focus is now, evidenced by the U.S. Department of Transportation’s (DOT) recent efforts to advance CPNT solutions.
Last year, DOT put out a CPNT Request for Quote (RFQ), which came about five months after the initial Request for Information (RFI) that sought feedback on the availability of operationally ready (Technical Readiness Level or TRL ≥ 8) CPNT technologies to meet critical infrastructure needs when GPS service is not available, degraded or disrupted. Multiple contracts were awarded with solutions now in the texting phase.
O’Connor regarded the Volpe Center’s industry-wide field demonstration of CPNT technologies that took place in 2021 as a significant step forward as well. Eleven companies, including Satelles, participated in the demonstrations, where the goal was to gather information on PNT technologies that are ready to back up GNSS.
The work continues for the PNT community, and while there is no silver bullet, there are solutions available today that address the growing threats to GNSS. With 2024 likely to “go down in history as the year we all woke up and said, ‘Oh wow, GPS resiliency really is a problem,’” now is the time to push for adoption, O’Connor said. There’s no need to wait.
“Everyone recognizes this as a problem now. We need to encourage and drive adoption. No one should be picking winners,” O’Connor said. “It’s a layered solution and each industry needs different layers. Wireless operators shouldn’t be waiting for the federal government to choose the technology. They should be adopting technology now to suit their needs and solve their problems.”
Ultimately, adoption will be driven by economics and policy, O’Connor said.
On the policy side, the government now has the opportunity to show leadership, he said, and that began with Volpe testing and DOT’s funding that will help “prime the pump for these solutions.” The FAA also has taken steps to protect critical infrastructure by leveraging CPNT, announcing last year that Iridium STL will provide resilient timing synchronization to FAA data center facilities across the U.S., made possible by a five-year contract with L3Harris Technologies. The service will be available to more than three dozen L3Harris-operated communications network backbone nodes and a similar number of FAA facilities.
There’s also the economics to consider. While there is cost associated with adding resiliency to GNSS, it’s not a lot, O’Connor said, with more industries seeing it as a worthy investment.
“You have to think about what is the cost of the network going down for an hour, or a day,” he said. “Those are the kinds of questions the industry will be asking itself. That’s where the economics will come in.”
Institutions like Volpe and DOT are helping to create the path toward adoption, while companies like Iridium are developing and offering the solutions needed to create that layered approach to toughen and augment GNSS.
“What’s most important to the future is adoption,” O’Connor said. “It’s not new technology or enhancement or improvement. It’s driving adoption. When you drive adoption, innovation will happen more quickly. And that creates an ecosystem that can re-invest in those technologies.”
