When the Institute of Navigation (ION) brought GNSS+ back to the U.S. East Coast in September, Baltimore was the backdrop for a conference concerned with spectrum conflict and the next generation of navigation infrastructure. With two packed days on the exhibit floor, ION GNSS+ 2025 mixed technical research tracks, commercial updates and policy conversations in a way that underscored how central resilient PNT has become to everything from aviation and space to smartphones and autonomous vehicles.

At the center of the week was a historically minded plenary, “Galileo—A Journey of 30 Years,” delivered by two people who have progressed alongside Europe’s GNSS: Marco Falcone of the European Space Agency (ESA) and Jérémie Godet of the European Commission (EC). Rather than simply a programmatic update, the session walked the audience through three decades of political debates, technical challenges and engineering breakthroughs that turned a fragile concept into a fully global system delivering meter-level open-service accuracy, 20 cm high-accuracy service and near real-time Medium-altitude Earth Orbit Search and Rescue (MEOSAR) performance.

Their framing—“climbing a mountain” with a summit that always reveals a higher peak—fit neatly with the rest of the conference, where almost every track grappled with how to move GNSS beyond “good signals in clear sky” toward assured PNT in contested and cluttered environments.

Galileo as Case Study in Engineering and Governance

Falcone and Godet started in the 1990s, when GPS was declaring Initial Operational Capability (IOC) and GLONASS was operational—and Europe, as they reminded the room, had no navigation system at all. Early ESA and national studies converged on a two-step GNSS1/GNSS2 concept, but nothing could really move without three ingredients: a name, a clear ambition and political backing. The name “Galileo” and the civilian-focused, GPS-interoperable vision appeared in a 1999 European Commission communication, paired with an insistence on European strategic autonomy even as the system was designed to mesh tightly with GPS.

Getting from PowerPoint to space required political heavy lifting. Godet paid tribute to Loyola de Palacio, the Spanish Transport Commissioner he called the “real mother” of Galileo, who pushed the program through an initially hostile Transport Council asking why Europe needed its own GNSS when GPS was “free of charge.” Her approach of systematically addressing each member state’s objections on cost, NATO security and duplication set a tone the program would repeat for decades.

The governance upheaval around 2007 to 2010 will have sounded familiar to many in the room: An over-ambitious PPP model collapsed when private concessionaires balked at taking real risk, forcing a mid-course pivot to full public funding and a more classical ESA–EU division of labor. From there, the talk traced the first “Galileo-only” position fix, the Soyuz launch anomaly that stranded two satellites in eccentric orbits, and the 2016–2017 clock failures traced back to a 50-cent feed-through component. Each episode was treated as evidence that large, safety-critical systems live or die on the ability to change operations quickly without breaking legacy services.

The most sobering moment came with the 2019 ground-segment incident that corrupted the navigation message and forced a week-long service interruption.The independent inquiry and subsequent redesign—shorter restart times, a “navigation extending mode” that allows graceful degradation for up to a week and a full pre-operational chain shadowing major software release—mapped directly onto themes running through multiple ION tracks on continuity and graceful degradation.

More recently, the war in Ukraine and the loss of Soyuz access to Kourou triggered another round of improvisation: Ten built satellites went into long-term storage while Brussels and Washington negotiated the security framework that ultimately allowed launches 12 and 13 on SpaceX Falcon 9 from Cape Canaveral. That experience, Falcone stressed, compressed their launch campaign tempo and forced leaner processes, lessons now being taken back into Europe as Galileo returns to Ariane 6 for launch 14.

In its forward-looking portion, the plenary jumped from Galileo Second Generation—reprogrammable, fully flexible payloads with electric propulsion and inter-satellite links—to low-Earth-orbit (LEO) PNT “pathfinders” as a future third GNSS layer, and then out to Moonlight and Mars comm/nav architectures being co-defined with NASA and the Japan Aerospace Exploration Agency (JAXA). Taken together, these plans cast Galileo not as a finished system, but as the medium Earth orbit (MEO) backbone of a multi-layer, multi-orbit PNT ecosystem. Their closing “recipe” for success—political will, technical excellence, user-driven evolution, industrial strength and international cooperation—could just as easily have served as the conference’s motto.

Themes from the Program

Resilience, AI and multi-layer PNT were strongly reflected in the conference’s technical program and tutorials. Short courses on GNSS jamming and spoofing with LEO constellations as a fallback, signals of opportunity (SoO), ionospheric effects and space applications all picked up on aspects of the resilience story: interference is now assumed, and LEO, SoO and environmental monitoring are no longer niche topics but central planks. 

On the research side, tracks opened with sessions on navigation security and authentication, AI-driven positioning and robust navigation using GNSS, setting the tone for a week that treated jamming and spoofing as operational realities. Papers covered space-based RFI detection, spoofing detection assisted by specific force inputs, RAIM-like anti-spoofing methods and multi-modal signal classification for challenging environments. 

Artificial intelligence and modern estimation methods were everywhere: factor-graph optimization in tightly coupled GNSS/INS, hybrid physics-informed neural networks and deep learning for interference suppression, ionospheric scintillation prediction and context-aware positioning for low-cost receivers in urban canyons. Sessions on smartphones and wearables, autonomous land and sea-based applications and indoor positioning underlined how far GNSS+ has moved beyond its aviation-first focus into mass-market, edge-compute and robotics domains.

Alternative and complementary PNT got full track treatment: atmospheric effects on GNSS and LEO PNT, non-optical and optical approaches for GNSS-denied navigation, geomagnetic and tunnel positioning, and advanced processing of terrestrial and non-terrestrial SoO all pointed to a consensus that “GNSS alone” is no longer a serious design assumption for critical applications. At the same time, classic augmentation work remains vigorous, with papers on global Satellite-Based Augmentation System (SBAS) architectures, Dual-Frequency Multi-Constellation (DFMC) integrity, ionospheric monitoring for GBAS and the modernization of network RTK services to ride out the looming solar maximum.

LEO PNT, referenced in the Galileo plenary as “GNSS3,” was one of the week’s hot topics, with dedicated sessions on LEO satellites for PNT, integrating LEO for enhanced positioning and atmospheric impacts on LEO-based systems. The technical content there dovetailed with Godet and Falcone’s vision of a future where MEO GNSS provides the timing backbone while LEO constellations add power, bandwidth and geometry for robustness and fast convergence.

On the Show Floor: A Dynamic Ecosystem

Those themes carried over into the exhibit hall, where the evening reception “30 Years of Galileo” gave the anniversary a more informal stage amid booths from ESA, DLR, receiver and simulator vendors, timing specialists and the Resilient Navigation and Timing Foundation. Hardware testbeds for spoofing and jamming, compact multi-band GNSS antennas, MEMS inertial units, timing oscillators and real-time PPP-RTK correction services sat alongside new-space LEO PNT players such as Xona.

GNSS is no longer a fragile, single-system asset but a set of global constellations, terrestrial backups and emerging LEO and lunar layers that must be engineered, governed and funded as a whole. The story Falcone and Godet told of difficult political choices, technical challenges turned into features and decades-long continuity of expertise, is now being replayed at new altitudes and in new orbits. For a community gathered in Baltimore to talk about the next 30 years of PNT, that combination of learning from the past and ambition for the future was exactly the signal they came to hear. 

The post ION GNSS+ 2025: Galileo at 30 and the Future of Resilient PNT appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

The Navigation Technology Satellite-1(NTS-1) and NTS-2 launched in the 1970s provided the backbone for the GPS services we rely on today, in military and civil contexts. The systems confirmed the accuracy and reliability of satellite-based atomic clocks, providing the timing element foundational to positioning, navigation and timing (PNT). The effects of relativity on the onboard cesium atomic clocks were measured and corrected such that a GPS receiver on Earth could validate the rate of GPS time was the same as Coordinated Universal Time (UTC).

In 2019, the Department of the Air Force designated NTS-3 as one of three initial Vanguard programs to innovate solutions to the unique 21st century threats to GPS availability and reliability. After several years of delays, NTS-3, developed by L3Harris, is nearing its launch date aboard the ULA Vulcan Centaur rocket. While experimental in nature, the capabilities around resilient PNT that NTS-3 will be testing are mission critical to maintaining navigation signal integrity and reliability in contested environments where GPS is constantly jammed or degraded. NTS-3 is intended to demonstrate the value of multilayer resiliency and prove critical technologies engineered to counter and mitigate the threat posed by the denial and degradation of PNT.

“NTS-3 is the first U.S. experimental, integrated navigation satellite system to demonstrate and test technologies for implementation in future GPS missions,” said Andy Builta, vice president and general manager, Surveillance Systems, L3Harris. “This is also the first U.S. SATNAV system to integrate phased array technology that enables simultaneous transmission of Earth-coverage and high-power, independently configurable regional beams, which will allow operators custom responses in diverse areas of operation.”

GPS’ Loyal Wingman

Described by L3Harris as a “loyal wingman” to GPS, NTS-3 will on-orbit test a suite of technologies all engineered to enhance the stability, availability, integrity and accuracy of military PNT. It will be in geosynchronous orbit for one year, operating outside of the live GPS system to safely test and experiment without impacting any current operations powered by or relying on GPS. NTS-3 relies on three interdependent segments—the space-based experimental satellite, a ground-based command and control system and agile software-defined user receivers. An underlying premise to all the segments is they can be evolved over time using software solutions, not requiring new hardware to combat future threats.

The technology embedded on the satellite includes the Agile Waveform Platform (AWP). AWP is comprised of enhanced signal processors (ESPs) and ground mission applications (GMAs). The ESPs are modular and fully re-programmable while on-orbit, providing the flexibility to support new signal types. This flexibility is designed to enable advanced concepts of operations, effectively countering existing threats as well as futureproofing against emergent threats yet to be encountered. The cloud-based GMAs allow operators to plan, configure and control Earth-based coverage over a wide geographical area.

The Cion antenna/receiver facilitates autonomous navigation by processing Space Service Volume (SSV) data from multiple GNSS and is fully re-programmable on-orbit. The Hosted Payload Processor (HP2) handles uploads from the ground, as well as providing payload health and status information. HP2 autonomously detects and corrects clock irregularities, increasing resilience in contested environments through its autonomous operation when ground control is lost for extended periods. 

An Active Electronically Steerable Phased Array (AESA) simultaneously transmits Earth-coverage and high-power regional beams, allowing for fully bespoke responses in different areas of operation. These beams combat GPS jamming, therefore enabling a greater diversity of mission sets. The system is provisioned with multiple atomic clocks and timing sources onboard that can be used independently and as an optimized ensemble to allow for automatic clock error detection and correction.

The ground control segment was designed to move from systems designed for a single mission and with limited applicability to different space systems, to a modular command and control architecture with software components that can support multiple Department of Defense (DOD) satellite systems. It will take advantage of commercially available ground antennas and monitoring receivers, improving the opportunities for satellite contact time by not relying upon the limited resources of government antenna equipment. 

An overall Modular Open Systems Architecture (MOSA) design philosophy ensures situational awareness in the field will be enhanced through flexibility, re-programmability and data standardization protocols. 

The user segment will leverage MITRE’s Global Navigation Satellite System Test Architecture (GNSSTA) for laboratory-grade software-defined receivers (SDRs) that can take full advantage of the system’s on-orbit signal re-programmability. AFRL emphasizes the user segment is the critical point where the in-theater individuals experience the impact of the space-based infrastructure’s experimental flexibility and expanded options.

“NTS-3 leverages industry standards along with commercial form factors and interfaces to provide a modular, scalable and host-agnostic payload,” Builta said. “Due to this, L3Harris was able to complete the design and build of NTS-3 three times faster and at a significantly lower cost than traditional programs.”

Chimera

NTS-3 will also test the Chips Message Robust Authentication (Chimera) signal authentication protocol developed by AFRL. Chimera involves encrypted, steganographic watermarks that are encoded into the signal by the satellite. Chimera was designed to verify satellite orbit data and validate the range between the satellite and user, providing protection against GPS spoofing by sending a signal that can be decoded by a key sent soon after. When a key is sent the system changes the key. Because the signal is in the user’s receiver before the key is sent, a spoofer will not have the correct key ahead of the real signal going out, making spoofed signals easily detectable. The spoofer won’t have the watermarks, or the watermarks and key won’t match up. 

The keys can be delivered via the GPS signal itself, which involves a 3-minute delay, or through other faster channels like an augmentation system or an internet connection. Future versions of Chimera can be uploaded to the satellite at any point, based on the emergence of new spoofing threats and strategies. 

Catching up to Threats

As NTS-3 prepares to launch on the ULA Vulcan Centaur, the capabilities of its experimental technologies are in greater need than ever before. Adversarial jamming and spoofing have become increasingly sophisticated, making it critical to provide in-theater warfighters with the ability to both receive and broadcast signals. 

“As the prime contractor, L3Harris is responsible for the design, development, integration and test of the NTS-3 space vehicle, as well as supporting integration with the control and user segments, launch vehicle integration and on-orbit operations,” Builta said. “As an unclassified experimental satellite, NTS-3 will conduct a year of experimental operations that provide on-orbit characterization of the technology and results that will inform future roadmaps and architectures.” 

He continued: “As NTS-3 readies for launch, we look forward to seeing how its cutting-edge capabilities will be critical to update 20th century technology for the 21st century threats that contested, degraded and denied PNT poses to our country’s national security.” 

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