Inertial Sense will be integrated into Hexagon’s Aerospace & Defence Division, where its compact, tactical-grade solutions are intended to extend the company’s resilient navigation capabilities in GPS-challenged environments. The acquisition targets growth in autonomy, aerospace, and defence markets.

“Inertial Sense brings exceptional GNSS+INS innovation that advances our assured PNT roadmap and expands resilient positioning capabilities in GPS-challenged environments,” said Stig Pedersen, President of Hexagon’s Aerospace & Defence Division.

Walt Johnson, CTO and founder of Inertial Sense, said the company looks forward to expanding access to lightweight, affordable, and precise navigation solutions through the Hexagon platform.

The post Hexagon Completes Acquisition of Inertial Sense appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

GNSS interference is named alongside long-range weapons systems, counter-UAS, and advanced air defense technologies as risks that international law alone has proven insufficient to address.

ICAO Secretary General Juan Carlos Salazar made the assessment at the opening of the 2026 World Overflight Risk Conference in Valletta, Malta, telling delegates that emerging military capabilities are creating an environment where civilian aircraft face heightened risk of being targeted or caught in crossfire. “We must now reach beyond the boundaries of aviation as we have known it,” Salazar said.

Salazar pointed to the recent Middle East crisis as both a demonstration of the aviation industry’s adaptability and evidence of the limits of operational workarounds. More than ten states partially or fully closed their airspace during the escalation, and while ICAO’s regional contingency frameworks helped coordinate rerouting, the Secretary General characterized these measures as costly and temporary rather than solutions to the underlying security threats.

The organization is pressing states to take three immediate steps: share threat intelligence rapidly when activities pose risks to civilian aircraft, strengthen risk assessment mechanisms and decision-making timelines, and improve coordination between military and civilian authorities to prevent misidentification. ICAO is also finalizing a Global Crisis Management Framework and updating its Manual Concerning Safety Measures relating to Military Activities and its Risk Assessment Manual for Civil Aircraft Operations Over or Near Conflict Zones.

Salazar grounded the legal case in ICAO Assembly Resolution A42-4 and Article 3 bis of the Chicago Convention, which explicitly prohibits the use of weapons against civilian aircraft, while acknowledging that the framework has not kept pace with regional conflict.

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The functionality will be available as a software option for the R&S SMBV100B and R&S SMW200A vector signal generators, giving device manufacturers a production-ready pathway to test and validate receiver compatibility with Pulsar signals ahead of the constellation’s commercial deployment.

Pulsar is designed to complement existing GNSS infrastructure — including GPS — by leveraging LEO orbital geometry to deliver stronger signals, improved accuracy, and enhanced resilience against jamming and spoofing. Where legacy GNSS constellations operate in medium Earth orbit at altitudes above 20,000 kilometers, LEO satellites orbit at roughly 500 to 2,000 kilometers, resulting in significantly stronger received signal power and reduced signal travel time. The tradeoff is that individual satellites pass overhead quickly, requiring a larger constellation to maintain continuous coverage — which Xona is building toward commercial scale.

The practical challenge Rohde & Schwarz is addressing is the test gap that precedes a new signal type’s deployment. Before device manufacturers can build and certify receivers that support Pulsar, they need the ability to simulate Pulsar signals in a lab environment — verifying receiver performance against known signal parameters without requiring an operational constellation overhead. Adding that simulation capability to established signal generator hardware provides an accessible, production-scalable route for validation.

“Navigation technology is entering a period of rapid evolution,” said Matt Hammond, North America Satellite Technology Manager at Rohde & Schwarz. “By adding Pulsar signal simulation to our signal generator portfolio, Rohde & Schwarz is preparing our customers for the next evolution of satellite navigation.”

“Test and measurement solutions play an important role in enabling device manufacturers to evaluate compatibility as new signals become available,” said Bryan Chan, co-founder and VP of Strategy at Xona Space Systems. “Rohde & Schwarz brings deep expertise in precision signal generation that helps make this possible.”

The R&S SMBV100B and R&S SMW200A will join Pulsar’s verified ecosystem program, which recognizes devices and test solutions validated for compatibility with Pulsar signals. Rohde & Schwarz showcased its navigation test solutions at Space Symposium 2026 in Colorado Springs this week.

The post Rohde & Schwarz Adds Pulsar Signal Simulation to Vector Signal Generator Portfolio appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

MATTEO PAONNI, ANDREA PICCOLO, LUCA CUCCHI, FRANCESCO MENZIONE, EUROPEAN COMMISSION, JOINT RESEARCH CENTRE (JRC),  OTTAVIO M. PICCHI, EXTERNAL CONSULTANT FOR EC, JRC, STEFAN WALLNER, MARCO ANGHILERI, CÉSAR VAZQUEZ ALOCÉN, PIETRO GIORDANO, EUROPEAN SPACE AGENCY, OLIVIER JULIEN ADVISOR FOR EUROPEAN COMMISSION, DG DEFIS

Exploiting GNSS signals and services has been a major technical development of the last few decades, enabling a large variety of applications to use position, navigation and timing (PNT) information. Starting with GPS and followed by other global and regional GNSS, a multiplicity of signals is now available to worldwide users in the available spectrum allocations concentrated in the L-band. Radio-Frequency Compatibility (RFC)—a concept formally defined many years ago by the International Committee on GNSS (ICG) of the United Nations Office for Outer Space Affairs (UNOOSA)—has been a cornerstone for the coexistence of GNSS signals in any chipset or receiver. These systems can be exploited at user level to provide unprecedented position accuracy and availability, and in some cases even benefit from interoperable signals to achieve superior performance compared to what any single system can do on its own.

Implementing RFC among the GNSS is mostly left to the various system providers, which act upon provisions of the Radio Regulations, established under the International Telecommunication Union (ITU), such as Resolutions 609 and 610 [1,2]. Providers use well-established methodologies to assess compatibility, shaped over many years, that consider the specific characteristics of GNSS systems. These methodologies have been defined considering emissions from Medium Earth Orbit (MEO) and Geostationary Orbit (GEO) satellites, assuming typical power levels on ground within a certain range. 

More recently, novel concepts have been developed to provide PNT signals from satellites in Low Earth Orbit (LEO), generally referred to as LEO PNT. These concepts include exploitation of frequency diversity by transmitting navigation signals in alternative frequency bands such as UHF, the Radio Determination Satellite Systems (RDSS) S-band, or Radio-Navigation Satellite Systems (RNSS) C-band. Most of these new systems also incorporate L-band signals to aid legacy user service adoption. Some LEO PNT initiatives have chosen signals in the L-band at received power levels comparable to classic GNSS, while others are considering significantly higher levels.

This, combined with the fact the world economy now relies heavily on GNSS, makes it crucial to assess the RFC of LEO PNT signals with the billions of terminals that have been designed to process signals transmitted from MEO and GEO satellites. Additionally, it is essential to verify the applicability of well-established methodologies to this new category of signals and systems, with different orbital characteristics and potentially significant variations in power levels at the user terminal input.

This article investigates Radio Frequency (RF) compatibility among LEO PNT and classic GNSS, focusing on the impact at user level and ways to ensure existing and future GNSS receivers will be able to operate reliably in the presence of multiple signals transmitted by LEO PNT systems. To ensure compatibility with existing GNSS, LEO PNT signals shall not cause harmful interference that degrades GNSS receiver performance, which is typically measured by the effective C/N₀ level. We pay specific attention to RFC in L-band RNSS allocations, which is already densely populated by many regional and global PNT systems.

Compatibility as a Key Prerequisite for Interoperability 

In the last 20 years, with the proliferation of global and regional GNSS, compatibility has been the central pillar to ensure these systems can be developed and operated without mutually interfering. GNSS providers have prioritized compatibility to ensure their coexistence and in 2007 agreed on a unified framework to define compatibility under the ICG, recognizing compatibility as a critical enabler of interoperability. By harmonizing technical standards and operational practices, the ICG laid the groundwork for global users to leverage multiple GNSS systems without compromising performance or reliability.

At its core, compatibility refers to the ability of space-based PNT services to function independently or in combination without causing mutual interference. This principle ensures signals from different GNSS systems can coexist in the RF spectrum while maintaining their individual characteristics and performance. For users, compatibility translates into robust, uninterrupted access to GNSS services, which is vital for applications ranging from aviation and maritime navigation to precision agriculture and autonomous vehicles. Achieving this requires meticulous coordination among GNSS providers to mitigate risks of signal degradation or service disruption.

A key driver behind this focus is the scarcity of RF spectrum allocations for GNSS. As the number of providers and their demand for spectrum grows, the RF bands reserved for satellite navigation face increasing congestion. This is particularly true for the so-called E1/L1 band (1559-1610 MHz) and E5 band (1164-1215 MHz) [3]. GNSS providers, therefore, must adopt a cautious approach to compatibility to safeguard these critical spectrum resources. This involves rigorous analysis of signal characteristics, orbital parameters and interference thresholds to prevent mutual degradation. 

Assessing RFC is a multidimensional task that requires balancing technical, operational and regulatory considerations. The primary objective of RFC analysis is to protect GNSS users by ensuring signals can be processed effectively. This involves evaluating potential interference scenarios, modeling signal interactions, and defining mitigation strategies. Over the years, methodologies for RFC assessment have evolved to incorporate modeling tools and standardized assumptions, including a dedicated methodology established under ITU-R M.1831[4]. These include:

• Orbital and signal parameters: modeling of satellite orbits, signal structures (e.g., modulation schemes, bandwidths) and transmission frequencies

• Payload and antenna characteristics: modelling of relevant satellite payloads characteristics, including antenna radiation patterns and power levels

• User receiver models.

Two critical metrics are central to RFC computations: Spectral Separation Coefficients (SSC) and Aggregate Gain (G_agg). The SSC is the primary tool to assess the potential risk of interference between two signals due to their capability to share a frequency band efficiently.

The G_agg represents the equivalent gain to be considered when a certain power is transmitted by a satellite constellation with certain transmitting antenna characteristics and specific orbital parameters and received by a receiver with a representative antenna pattern.

Over the last 20 years, RFC assessments have focused on GNSS systems transmitting signals from MEO, which is commonly adopted by all global systems, and from GEO and IGSOs/HEOs, used by regional systems and satellite-based augmentation systems (SBAS). It is essential to ensure methodologies, standard assumptions and typical use cases are adequate once new systems are transmitting from LEO.

LEO PNT Key Differentiators 

LEO PNT systems represent a transformative approach to satellite navigation, offering distinct advantages such as providing enhanced signal strength at ground level, which can be obtained more efficiently than from MEO altitudes thanks to the reduced distance to the final users and hence smaller free-space propagation losses. These constellations can also offer improved coverage in urban and high-latitude regions, therefore complementing traditional MEO constellations. However, these systems also introduce unique compatibility challenges that necessitate rigorous evaluation to ensure harmonious coexistence with existing GNSS. 

LEO satellites operate at significantly lower altitudes than the MEO altitudes of traditional GNSS. This proximity to Earth enables LEO PNT systems to potentially ensure higher ground signal strength, which enhances signal robustness. However, this advantage comes with a critical caveat: High power levels from LEO satellites can interfere with legacy GNSS receivers, which are designed to operate with extremely weak signals from MEO satellites (typically in the range of –150 dBW to 160 dBW in the case of open, unobstructed reception). 

The dynamic nature of LEO orbits introduces additional complexities for receiver design. LEO satellites move rapidly relative to Earth, resulting in significant Doppler shifts and short visibility periods. From a compatibility perspective, based on available information regarding forthcoming LEO PNT systems [9], the number of simultaneously visible satellites is expected to be higher than that of legacy GNSS. This results in an increased number of transmitters operating within the same spectrum bands.

Two scenarios warrant particular attention: 

1. Impact on legacy GNSS users: The coexistence of high-power LEO signals with weak MEO signals in shared bands (e.g., E1/L1) could degrade legacy GNSS receiver performance. For instance, a LEO transmitter operating at +10 or even +20 dB in the E1 band could overwhelm a GNSS signal at –160 dBW, even with substantial spectral separation. 

2. Compatibility for space users: LEO PNT systems also must avoid interfering with other space-based receivers in LEO, which often rely on GNSS signals for autonomous navigation and other critical functions. 

The impact from high power might be (partially) mitigated through spectral separation and other specific measures, but the risk remains high, so all factors must be carefully assessed. Spectral separation represents a key design tool to minimize interference among two signals transmitted within the same band, and the choice of the carrier frequency remains highly critical. However, the spectrum currently allocated to RNSS is very crowded, and the possibility to have completely isolated signals is extremely limited, especially when transmitted at high power. In this condition, spectral separation is never corresponding to complete isolation and, as such, especially in the presence of very high power levels, the impact might still be relevant. 

Spectral Separation

The RNSS E1/L1 band is increasingly congested with the presence of multiple signals from various global satellite constellations. Current band allocation is the result of decades of bilateral coordination, which has ensured highly compatible systems with good spectral separation among signals. It is aimed at enhancing interoperability among the systems, which often use the same carrier and spreading modulation. However, it is essential to note good spectral separation does not guarantee perfect signal isolation.

The Figure 1 left plot illustrates this concept, showing the spectral separation coefficients between existing GNSS signals transmitted by GPS, Galileo and BeiDou and a hypothetical additional BPSK(1) signal placed at various frequencies within the E1/L1 band. This plot presents the spectral separation coefficient for the BPSK(1) signal, while the right plot shows the same concept for a BPSK(2) signal. Both plots show how challenging it is to identify slots that ensure very high or high spectral separation with all existing signals in E1/L1, given the presence of a wide variety of signals transmitted in the band. In particular, the central part of the band is populated by several signals adopted for open services by most of the global and regional systems, while governmental signals from GPS, Galileo and BeiDou occupy higher frequency slots. Any offset between -20 and 20 MHz from the E1 carrier frequency results in an SSC above -80 dB/Hz with a given signal already transmitted in the band. It is important to note that even an SSC of -80 dB/Hz, which may seem low, corresponds to a certain degree of “non isolation,” which might become especially crucial in the case of a high power (or high aggregate gain) from the interfering signal/system. Leveraging spectrally efficient modulations, like what Xona plans to use, [5] can certainly help to improve the isolation. 

Beyond the potential impact related with compatibility, the actual added value of high power for final users is to be well understood, as system self-interference is also to be accounted for. The combined (positive) effect of increased power needs to be adequately assessed against the increased self-interference to avoid a saturation of the effective signal to noise ratio when the amount of satellites in view increases.

Consideration of High-Power Systems 

RF compatibility between a signal of interest delivered by constellation X and an interfering signal delivered by constellation Y relies on assessing the amount of noise created by inter- and intra-system interference. This noise is typically represented as an additional white noise at the correlator output that has a level equal to

Where 

is the maximum received power of the interfering signals, assuming all constellation satellites transmit at that power;

is the Spectral Separation Coefficient (SSC) between the interfering signal and the local signal used by the receiver to process the useful signal;

is the so-called aggregate gain and represents a coefficient that accounts for the aggregation of the power of all the interfering signals (including the effect of the user antenna) affecting the user receiver.

At the end, the total equivalent noise that will affect the reception of the useful signal can be modeled as a White noise with the following level:

Where

is the thermal noise affecting the receiver;

are the number of signal types broadcasted by the constellation delivering the useful signal of interest and the equivalent noise generated by these signal types, respectively;

are the number of signals broadcasted by other constellations and the equivalent noise generated by these systems, respectively.

Self-Interference 

Among the current GNSS signals used, let us look at GPS L1 C/A:

• It is one of the signals that leads to the highest SSC (-61.9 dB/Hz) regarding self-interference due to the frequency compactness of BPSK(1). 

• Accounting for a typical G_agg for a global system of 11 dB in an open sky situation 

• The typical maximum power for a GNSS system is in the order of -153 dBW.

Taking these values into account, GPS L1 C/A generates an additional equivalent self-interference White noise of about -203.9 dBW/Hz, which is slightly lower or equal to typical thermal noise (roughly between -200 and -204 dBW/Hz). Assuming the receiver thermal noise is at a level of -201.5 dBW/Hz, this means the GPS L1 C/A self-interference would increase the background noise (or equivalently, reduce the C/N₀) by about 2 dB if it was the only source of interference.

If the maximum received power of GPS L1 C/A was much higher, then self-interference would start dominating the thermal contribution. This would eventually result in background noise increasing at the same rate as the power of the useful signal. Figure 2 shows the expected C/N₀ (not accounting for the gain brought by the user antenna on the useful signal) as a function of the maximum power of the GNSS signal for a variety of modulation. The C/N₀ reaches a ceiling at some point due to self-interference. This ceiling depends on the modulation because each modulation will create a distinct SSC.

Another effect occurs during constellation build up. In this case, the amount of self-interference will also grow, which can be represented as a growth of the G_agg. This is illustrated in Figure 3 for a BPSK(1) signal. As the Gagg increases, the C/N₀ decreases. To better understand this figure, a G_agg of 3, 6 and 9 dB can be seen as equivalent to receiving one, two and four signals, respectively, at the indicated received power. For a high-power constellation, this decrease can be relatively steep, depending on the type of signal used. 

Figures 2 and 3 highlight that high power signals might not lead to the expected high C/N₀ for a typical MEO or LEO constellation in open sky situations. This has implications regarding the quality of the measurements, which would not be as improved compared to a “normal” system. Still, there are advantages to such high-power signals:

• If the receiver is not in an open sky situation, fewer satellites will be in view. This is equivalent to reducing the self-interference through a lower G_agg. So, in this case, the C/N₀ at receiver level would become higher, as shown in Figure 3.

• There is still a better resistance against interference compared to “normal” signals because this interference would need to be more powerful to have an effect on the C/N₀.

Finally, in a complicated environment where some signals will be received with a high C/N₀ while others are severally attenuated, it is possible the power difference between both types of signals becomes significant. Imagine a signal at 70 dB-Hz and another at 25 dB-Hz. Even though the power difference is 45 dB, both could be tracked. However, unless the isolation of the spreading codes is extremely good, the cross-correlation due to the signal with a high C/N₀ will be higher than the auto-correlation of the weak signal, thus making it difficult or unreliable to acquire/track the weak signal.

Sharing the Band

The previous section only considered self-interference, as if there was only a single constellation. However, many GNSS systems share the L-band. This brings diversity to users and requires compatibility. This means we must consider that users will not only suffer from self-interference, but also interference from other systems. If we consider these are only global systems with a G_aggof about 11 dB, then the level of additional noise created by these interferences will depend on the number of interfering systems, the power of the interfering signals and the SSC between signals.

Take the example of the compatibility between GPS L1 C/A and Galileo BOC(1,1) signals. Figure 4 represents the expected C/N₀ (not considering the effect of the receiving antenna on the useful signal) for a L1 C/A receiver and for a BOC receiver for a plurality of received powers for both signals (all signals of the constellation are assumed to have the same received power). Increasing the power of one of the two signals is always detrimental to the other; the area where both signals have a good C/N₀ is somewhere around the diagonal. Thus, it makes sense for the power of both signals to be roughly the same. So, if there’s a high-power signal in part of the band, other signals broadcasting there have to use high power signals, unless they are isolated spectrally. 

In reality, more than two signals or systems are typically considered in similar frequency bands, thus facilitating interoperability. Imagine there are three systems (for instance GPS/Galileo/BeiDou) all broadcasting BOC signals (data and pilot) for interoperability reasons, as is the case currently at 1575.42 MHz. Assuming all signals have roughly the same received power and G_agg, Figure 5 shows using high power signals would result in a higher loss on the C/N₀. This leads to a situation in which the C/N₀ is not so different between high power signals and “normal” signals (3dB difference in C/N₀ for a difference in the received power of 30 dB). This shows the current situation is well adapted and optimized for compatibility and interoperability. Note the band around 1575.42 MHz is even more crowded as it contains signals from GPS, Galileo, BeiDou, QZSS, NavIC, SBAS, etc. In such a situation, it is questionable whether it makes sense to have high power signals.

The Case of LEO GNSS Space Users 

In traditional GNSS operated from MEO satellites, space-based users experience similar signal reception characteristics to ground users in terms of received power, G_agg, and C/N₀ degradation. This assumption no longer holds when GNSS is operated from LEO satellites, which are slightly above the altitude of space-based users. To evaluate the power variation, Table 1 analyzes individual contributions for a reference ground user and three GNSS space users at different altitudes, corresponding to three EU Copernicus Sentinel satellites currently flying at about 600, 700 and 800 km, respectively [6]. The single satellite power increase was computed by accounting for the reduced path loss, while the G_agg was computed assuming the receivers move on a sphere with a radius equal to the sum of the Earth’s radius and the victim satellite’s altitude. As the space user approaches the interfering constellation orbit altitude, the number of simultaneous interfering satellites decreases, leading to a reduced G_agg. By combining the single satellite power increase with the reduced G_agg, we can determine an approximate increase in interference power from the alternate system a space user would experience with respect to a ground user. Table 1 shows that, for Sentinel 3A, the interference increase can be up to nearly 10 dB. This increase might have significant implications for GNSS receiver performance. This kind of impact should be carefully considered in the design and operation of LEO-based GNSS systems.

Interference Impact on Space Receivers

The risk of interference from an alternate system on GNSS signal reception can be significant when the system transmits from LEO orbits instead of MEO.

An increasing number of space missions use GNSS space receivers for constellation management and to provide their services. Earth observation satellites like the Sentinels of EU Copernicus system use Precise Orbit Determination (POD) [7] based on GNSS observables for georeferencing their images; communication satellites like Starlink and OneWeb might take advantage of GNSS reception for timing and pointing their inter-satellite links as well as for beam pointing. For scientific missions like GRACE-FO, Swarm and ICESAT-2, GNSS POD is required to perform the measurements. 

A higher noise floor caused by receiving high-power navigation signals from LEO would cause GNSS space receiver accuracy to degrade, with a direct impact on these missions.

The undesired effects are a degradation in the quality of data provided as well as issues in data distribution among satellites caused by poor inter-satellite network synchronization. Also, constellation management and collision avoidance manoeuvres rely on the accuracy of GNSS-based measurements and would suffer in harmful interference scenarios.

On top of this, there is another category identified as “super-users” who exploit GNSS for operations and service provisions. Notably, LEO PNT providers operate in the low Space Service Volume (SSV) and LEO region [8] at an altitude that exceeds several LEO missions. LEO PNT systems with a constellation altitude lower than one of the alternate systems might be heavily impacted on GNSS signal reception. LEO PNT relies on GNSS signal measurements for several key navigation payload functions. Unlike other GNSS, the Orbit Determination and Time Synchronisation function is not based on the observables collected by a ground network of receivers, but is largely based on space receiver measurements which, depending on the particular architecture, are processed on-board the satellite or downlinked to the ground segment to compute the LEO PNT satellite’s accurate orbit and clock.

This information is used by the on-board timing subsystem to estimate the offset of the onboard clock with respect to GNSS time (and possibly steering the clocks to the desired timescale) as well as to estimate the satellite orbit and generate the navigation message parameters to be broadcast to LEO PNT users to compute their PVT solution.

In [9], Earth Observation Copernicus Sentinels are considered critical GNSS users in space. In the paper, a visibility analysis assesses the potential impact “super-users” might be subject to and focuses on ensuring uninterrupted operation of these critical space-based assets. It also demonstrates how the potential risk is not related to short or temporary “collisions,” but rather the continuous exposition to a potentially very high amount of interference from a relatively short distance.

Therefore, degraded GNSS space receiver accuracy caused by interference can significantly impact the quality of the generated LEO PNT signals as their frequencies, PRN codes, navigation message timestamps and orbit and clock corrections are all based on it. 

Degradation of GNSS space receiver accuracy would result in a higher value of the Signal-In-Space-Error contribution and a degradation of the PVT solution computed by users.

An Example of Interference in Space

Through the Copernicus program, The European Union (EU) is operating a fleet of Earth Observation satellites, referred to as Sentinel satellites. The satellites embark GNSS space receivers that provide Galileo and GPS code and phase iono-free measurements for POD and Time Synchronization (TS).

The detailed assessment in [10] showcases how ground based interference is measurably impacting space receivers on LEO satellites, although the GNSS antenna is mounted on the relevant satellites facing in zenith direction. The interference originates from the ground and affects a short portion of the satellite’s trajectory. In a future scenario, a comparable level of interference may originate from satellites emitting RNSS signals at a slightly higher altitude compared to the Earth observation satellite. In such a case, the direction of the interference would align with the pointing of the Earth Observation’s GNSS antenna; no favourable low gain of the antenna would reduce the level of interference. 

Figure 6 shows the C/N₀ average as measured by the Sentinel 2C on-board GNSS receiver for the Galileo E1-C signal component as a function of the satellite’s ground track in February 2025.

A clear reduction in C/N₀ over eastern Europe can be identified. It ranges up to a level of approximately 4 dB. This reduced C/N₀ can be attributed to the jamming events occurring over the corresponding region. 

The impact of the interference event on February 1, 2025, on the real-time PODTS (in blue for the broadcast products and in orange for the Galileo High Accuracy Service (HAS) [11] products) is shown in Figure 7. The red vertical lines indicate the start of the interference event. The plots show the kinematic TS and POD performance respectively. The error increases in both cases until the number of satellites is not sufficient to compute position or time. The kinematic method cannot cope with measurement gaps (in this case only four satellites were available). The impact of the interference on both POD and TS is clearly evident.

Conclusions 

The use of high-power signals transmitted from LEO satellites can provide interesting performance benefits when considered in isolation. However, when multiple systems transmit signals in the same frequency slot, it can lead to interference and performance degradation. To avoid this, most systems would need to use high-power signals, which would ultimately lead to a decrease in overall performance and hardly sustainable spectrum consumption.

A careful approach to compatibility has been a fundamental factor to ensure protection of the very scarce and increasingly crowded spectrum allocations available to GNSS providers. 

• GNSS providers adopted key principles for open/commercial signals in L-band

• Sharing the band without exclusive use of a spectrum portion 

• Interoperability at user segment level is enabled by compatibility at system level.

The risk of a “power race” among commercial providers in legacy GNSS bands (E1/L1 and E5/L5) could disrupt these practices and penalize legacy users as well as future providers willing to access the spectrum. Among various risks, a power escalation could prevent other providers from using this part of the band without significant degradation.

The exploitation of GNSS by space users in LEO poses a significant risk, particularly for space service users like the Copernicus Sentinels. These aspects must be carefully assessed, and the case of space users should be studied in detail when evaluating compatibility between MEO GNSS and LEO PNT systems.

It is essential that all new LEO PNT providers ensure a sustainable approach to spectrum. Multilateral fora, such as the International Committee on GNSS (ICG), and GNSS providers can help build guidelines to ensure long-term sustainable spectrum access for the benefit of users and potential future providers.

Regulatory elements, such as ITU Resolution 609 and Recommendation 608, exist to help keep the level of interference low and prevent one system from dominating the available margin to the emission limit. These instruments are essential for ensuring spectral sustainability and should be respected by all operators. 

Acknowledgements 

This article is based on material presented in a technical paper at ION GNSS+ 2025, available at ion.org/publications/order-publications.cfm.

References 

(1) Resolution 609 (Rev.WRC-07) Protection of aeronautical radionavigation service systems from the equivalent power flux-density produced by radionavigation-satellite service networks and systems in the 1 164-1 215 MHz frequency band, RES609-1 (2007). https://www.itu.int/en/ITU-R/space/Res609%20CM%20Documents/RES-609_e.pdf

(2) Resolution 610 (REV.WRC-19) Coordination and bilateral resolution of technical compatibility issues for radionavigation-satellite service networks and systems in the frequency bands 1 164-1 300 MHz, 1 559-1 610 MHz and 5 010-5 030 MHz, RES610-1 (2019). https://www.itu.int/en/ITU-R/space/Res609%20CM%20Documents/RESOLUTION%20610%20(Rev%20WRC-19).pdf

(3) European Union. (2023). European Union, Galileo Open Service Signal-In-Space Interface Control Document (OS SIS ICD). https://www.gsc-europa.eu/sites/default/files/sites/all/files/Galileo_OS_SIS_ICD_v2.1.pdf

(4) Recommendation ITU-R M.1831-1 (09/2015) A coordination methodology for RNSS inter-system interference estimation, M.1831-1 (09/2015) (2015). https://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.1831-1-201509-I!!PDF-E.pdf

(5) Reid, T. G. R., Neish, A. M., Walter, T., & Enge, P. K. (2018). Broadband LEO Constellations for Navigation. NAVIGATION, 65(2), 205–220. https://doi.org/10.1002/navi.234

(6) Sentinel Online. (2025). Copernicus Programme. https://sentinels.copernicus.eu/web/sentinel/copernicus

(7) European Union. (2025). Copernicus Operations—POD in details. https://sentiwiki.copernicus.eu/web/precise-orbit-determination

(8) FrontierS. (2024). State of the Market Report, Low Earth Orbit Positioning Navigation and Timing–2024 Edition. frontiersi.com.au

(9) Paonni, M., Picchi, O. M., Piccolo, A., Cucchi, L., Menzione, F., Wallner, S., Anghileri, M., Alocén, C. V., Giordano, P., & Julien, O. (2025). On the Compatibility of GNSS User Segment with Emerging LEO-PNT Systems and Signals. Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), 915–928. https://doi.org/10.33012/2025.20406

(10) De Oliveira Salguiero, F., Lapin, I., Cordero Limon, M., Caparra, G., & Garcia Molina, J. A. (2025, September). Impact of Ground-Based Interference on GNSS Space Receivers On-Board LEO Satellites. Proceedings of the 37th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2024).

(11) European Union, ‘European GNSS (Galileo) High Accuracy Service Signal-In-Space Interface Control Document (HAS SIS ICD)’. (2022, May). https://www.gsc-europa.eu/sites/default/files/sites/all/files/Galileo_HAS_SIS_ICD_v1.0.pdf.

Authors

Matteo Paonni is Deputy Head of the Space, Connectivity and Economic Security Unit at the Joint Research Centre of the European Commission in Ispra, Italy. He coordinates JRC technical and policy support to the EU Satellite Navigation Programmes within the European Commission. Matteo is also the chairman of the Galileo 2nd Generation Signals Task Force (G2G-STF), established under the EU Space Programme. Before joining JRC in 2013, he was a research associate at the Institute of Space Technology and Space Applications at the University of the Federal Armed Forces in Munich.

Ottavio M. Picchi holds an MSc in Telecommunications Engineering and a Ph.D. in Information engineering, both from the University of Pisa. Since 2012, he has worked in signal processing for communications and navigation. He is an external consultant for the European Commission’s Joint Research Centre, focusing on Fused PNT systems, 5G NTN, IRIS2 and RF compatibility.

Andrea Piccolo is a Technical and Scientific Officer at the European Commission’s Joint Research Centre in Ispra, Italy. His specialties include GNSS spaceborne receivers, space service volume, LEO PNT, Galileo PRS, and developing new Galileo services. He graduated with an M.Sc. in Telecommunications Engineering from Politecnico di Milano in 2014. He worked as a Radio Navigation System Engineer at Thales Alenia Space Italy, focusing on GNSS Spaceborne receivers and Galileo Navigation Signal Generation Unit (NSGU) product development from 2015 to 2023.

Luca Cucchi is a GNSS Security and Galileo PRS Security Officer at the Joint Research Centre (JRC) of the European Commission in Ispra, Italy. He coordinates the activities of the JRC Galileo PRS User Segment Laboratory and provides support to the Directorate-General for Defence Industry and Space (DG DEFIS) and EU Agency for the Space Programme (EUSPA) on Galileo Program activities. He has 14 years of experience in the private sector as a radio navigation engineer, primarily focusing on the Software Defined Radio approach. He earned his Master’s Degree in Telecommunication Engineering from the University of Pisa in 2005.

Francesco Menzione received a master’s degree (2012) and Ph.D. (2017) from the University of Naples Federico II in Aerospace Engineering and Satellite Navigation. From 2012 till 2021, he worked in the aerospace sector as a navigation and control engineer. In 2021, he joined European Commission’s Joint Research Centre as Technical and Scientific Officer. In this role, he provides technical and project management support for various DEFIS-funded studies and research areas, with a focus on Precise On-Board Orbit Determination using HAS, Space Service Volume, LEO-PNT, Hybrid PNT, 5G-NTN, LEO-based RFI monitoring, and GNSS-based remote sensing.

Stefan Wallner is the Head of the Galileo Signal-in-Space Engineering Unit within the Navigation Directorate at the European Space Agency. He graduated with a Diploma in Mathematics from the Technical University of Munich and was research associate at the University of the Federal Armed Forces in Munich. He has worked at the European Space Agency since 2010 and is responsible for the Galileo Signal in Space and Performance Engineering activities within ESA.

Marco Anghileri is the satellite Payload Manager of Celeste, ESA’s program for satellite navigation in Low Earth Orbit. He has more than 20 years of experience in satellite navigation across academia, industry and the European Space Agency. He began his career in 2005 at the Universität der Bundeswehr München, contributing to Galileo signal innovations later adopted in both first- and second-generation systems. He served as Lead Systems Engineer and Project Manager at IFEN GmbH and Airbus Defence and Space, where he led international R&D activities on future GNSS signals and system architectures for ESA and the European Commission. From 2021 to 2025, he was part of ESA’s GNSS Evolution team, conducting LEO-PNT system studies and technology R&D activities, while also taking responsibility for frequency management and security in the evolution of Galileo and EGNOS.

César Vázquez Alocén holds a M.Sc in industrial engineering from the University of Alcala (Spain). Since 2018 he has worked at ESTEC (ESA) in different roles, mainly working on GNSS signal design, signal processing algorithms and receiver testing activities, supporting several ESA navigation programs including Galileo and LEO PNT.

Pietro Giordano covers the role of LEO PNT system manager at the European Space Agency. Previously, he worked in Thales Alenia Space Italy before joining ESA/ESTEC in 2009. He worked several years within the Galileo project covering many roles, from user segment to operations, and in the ESA technical directorate as overall coordinator for spaceborne GNSS and space PNT technologies. He has been in charge of the definition and coordination of the European technology harmonisation roadmap for on-board radio navigation receivers and he supported Earth observation programs (e.g.: Copernicus/Sentinel). He contributed in the development of new concepts such as real-time on-board autonomous POD (P2OD concept), LEO PNT payloads, definition of new spaceborne GNSS receiver components (e.g.: AGGA family ASIC) and use of GNSS signals for lunar autonomous navigation. He was the chain lead for the navigation services within the ESA Moonlight program.

Olivier Julien is an advisor to the European Commission DG DEFIS on EU Satellite Navigation Programs where he supports the EU new initiatives on navigation and radio-frequency matters. From 2019 to early 2025, he was a Senior Principal Engineer in the Positioning technology team of u-blox (Switzerland). Before that, he was the head of the Signal Processing and Navigation research group of the TELECOM laboratory of ENAC (France). He received his engineering degree from ENAC and his Ph.D. from the University of Calgary (Canada).

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ESA launched the first two Celeste in-orbit demonstration satellites — IOD-1 and IOD-2 — on March 28, marking the agency’s first step toward extending satellite navigation into low Earth orbit. u-blox, working under ESA’s Navigation Innovation and Support Program (NAVISP) Element 2, is conducting a technical evaluation of how LEO signals interact with and augment established GNSS constellations such as Galileo.

The Swiss positioning firm frames LEO not as a replacement for GNSS but as an additional layer — one characterized by higher signal strength and rapidly changing satellite geometry that could accelerate convergence and improve robustness in challenging signal environments. Early integration work is underway on u-blox’s X20 GNSS platform, examining how LEO signals across multiple frequency bands can be incorporated into future receivers.

The scope of the NAVISP project includes characterization of emerging LEO signal transmissions, analysis of LEO-GNSS measurement interactions, and evaluation of how dynamic satellite geometry affects positioning performance.

“Our work within the ESA NAVISP framework allows us to better understand how emerging signal sources can complement GNSS and contribute to robust and reliable positioning performance,” said Jani Käppi, Head of Technology Positioning at u-blox.

The full Celeste demonstration constellation will ultimately comprise 11 satellites testing innovative signals across various frequency bands. ESA’s 2025 Ministerial Council further endorsed a next phase — an LEO-PNT In-Orbit Preparatory phase — and incorporated Celeste as one of three pillars of its new European Resilience from Space initiative. 

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The signal was received at 10:38 CET on April 8, 2026, and verified by ESA teams at ESTEC as well as at GMV’s monitoring station in Lisbon.

The milestone marks successful commissioning of the spacecraft and opens the operational experimentation phase of a program designed to test whether a complementary low Earth orbit navigation layer can enhance Galileo’s accuracy, resilience, and security. Celeste IOD-1 and a second demonstrator, IOD-2, were launched March 28 aboard a Rocket Lab vehicle from Launch Complex 1 in Mahia, New Zealand. The two satellites — built by separate European consortia, with GMV leading one and Thales Alenia Space the other — separated from the launch vehicle approximately one hour after liftoff. LEOP and commissioning activities for IOD-1 were conducted by an integrated GMV and Alén Space team from the mission control center in Tres Cantos.

Operating at altitudes between 500 and 560 km, the demonstrators will validate precise autonomous orbit determination without ground infrastructure dependence and will test navigation signal performance in L- and S-bands from LEO. The program’s rationale is multi-orbit resilience: by integrating a LEO constellation alongside Galileo’s medium Earth orbit architecture, Celeste aims to reduce vulnerability to interference and expand the envelope of advanced PNT services available to European users.

The IOD phase will comprise eleven satellites plus one in-orbit spare across both consortia. GMV holds prime contractor responsibility for six of the demonstrator satellites, covering system definition and design, space and ground segments, user segment, and operations. The two initial demonstrators are focused on securing registered frequency allocations and signal testing through the end of 2025. Eight larger follow-on satellites are under development, with subsequent launches targeting 2027 and the eventual fielding of a full operational fleet.

GMV was selected by ESA in 2024 to lead one of the two parallel Celeste development contracts.

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Institutional Escalation: ICAO and ITU Act

The most significant development for the GNSS community may be regulatory rather than technical. In October 2025, the International Civil Aviation Organization passed a resolution condemning GNSS interference originating from both Russia and North Korea as violations of the 1944 Convention on International Civil Aviation. The following month, the ITU’s Radio Regulations Board, at its 100th meeting, again urged Russia to “immediately cease any source of harmful interference” to safety services in the Radio Navigation Satellite Service — specifically interference affecting receivers in Estonia, Finland, Latvia, and Lithuania originating from Russian territory.

The Baltic situation had intensified steadily through the year. Lithuania coordinated a letter signed by 17 EU transport and digital ministers in June 2025 calling for a coordinated European Commission response. The European Council’s own data showed aircraft GNSS interference cases in Poland rising from 1,908 in October 2024 to 2,732 by January 2025. Estonia announced in July 2025 that Russia had moved jamming equipment to a site at Kingissepp, 20 kilometers from its border, and reported that GPS jamming had caused over €500,000 in damage in the preceding three months alone. Sweden’s Department of Transport stated that interference over the Baltic was occurring “almost daily” and had spread “both geographically and in scope.”

Active Conflict: Iran, India-Pakistan, Israel

The SWF report also documents the operational deployment of GNSS interference in three distinct conflict contexts in 2025.

During Iran’s 12-day war with Israel in June 2025, Iran jammed GPS over multiple metropolitan areas to counter drone and missile threats. Iran’s Deputy Communications Minister publicly acknowledged the disruptions were “for military and security purposes.” The Maritime Information Cooperation and Awareness Center estimated that 970 ships per day experienced GPS jamming in the Strait of Hormuz during this period, causing traffic through the Strait to drop by 20 percent as vessels limited transits to daylight hours. The report adds a technically notable January 2026 data point: during protests in Iran, Starlink ground terminals were found to have had their GPS units spoofed, causing packet losses of 30 to 80 percent. Users who switched to Starlink’s internal position estimates restored connectivity; SpaceX subsequently pushed a software update to mitigate the interference.

In South Asia, during India’s Operation Sindoor against Pakistan in May 2025, Indian electronic warfare forces were deployed specifically to interfere with GNSS signals to hamper Pakistani military aircraft navigation. The report notes that GPS spoofing has since migrated from the border zone into civilian airspace: more than 10 percent of flights in the Delhi region have reported spoofing incidents, and in November 2025 interference around Indira Gandhi International Airport was severe enough to divert flights to alternate airports.

Israel, for its part, entered into a formal commitment at the ITU in late 2025 to limit RNSS-interfering transmissions to situations involving imminent threats to life or critical infrastructure, capped at 15 minutes per incident — following a July 2025 meeting with Jordan and Egypt convened under ITU auspices.

The LEO Dimension

Perhaps the most technically striking finding for GNSS engineers: the report cites Aerospace Corporation research from July 2025 indicating that GPS jamming over Ukraine has created what researchers described as “a giant hole” in GPS coverage for small LEO satellites carrying onboard GPS receivers for position, navigation, and timing. The jamming environment over a conflict zone is now affecting space-segment PNT — not just ground users.

The Secure World Foundation’s Global Counterspace Capabilities 2026 is available here.

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“Celeste is a program that started not even two years ago, and we are already aiming to launch our first two satellites, what we call the IOD-1 and the IOD-2,” Giordano said. The satellites, now in orbit, are CubeSats flying at around 510 kilometers altitude.

“The objective of the mission is to demonstrate technology,” Giordano said. “This IOD [in-orbit demonstrator] phase is fundamental for us to master the technology, the techniques that we want to apply for future systems.” The satellites are designed to validate new positioning signals, multi-frequency capabilities, and integration with next-generation networks.

Giordano highlighted the wider scope of the Celeste program. “The two companies in charge of development are GMV and Thales Alenia Space France. They’re not just building the satellites. They’re also responsible for the ground segment and system-level development, including the very important specification phase, which will start as soon as the satellites are flying.”

Starting now

Celeste will operate across multiple frequency bands, Giordano said, “moving from UHF to other bands and potentially targeting indoor applications. Of course, L-band is a fundamental and master band we all need to provide. S-band has two phases: there is the S-band allocated to RNSS [radionavigation satellite services], used by GNSS systems today. But we may explore potentially usable MSS (mobile satellite service) bands, and will leverage 5G and terrestrial networks. “We also have C-band, one of the more appealing bands for resilience,” Giordano said, emphasizing the versatility and future-proofing of the system.

The IOD phase lays the groundwork for an operational LEO-PNT network. “At Ministerial ’25,” Giordano said, “ESA proposed the in-orbit preparation phase [IOP] that will follow.” First IOP satellites could be launched in the 2027-2028 timeframe. “When it comes to 5G and the current IOD satellites, we’re only testing the very basics, the physical layer,” Giordano said. “We will go beyond that in the IOP phase, where we plan to implement the full-scale 5G network capabilities.”

Looking ahead, Celeste is open to adding additional small constellations and experiments, offering opportunities for European industry and third-party participation. Giordano said, “We have a very strong ambition to bring into space operational services at European level in 2032, and we cannot do it with just demonstration satellites.”

With IOD-1 and IOD-2 now in orbit, ESA has taken its first tangible step toward a resilient, multi-band European LEO-PNT system, promising enhanced positioning, navigation, and timing services for the decades ahead.

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VIAVI Solutions and Ground Control have announced a partnership to integrate VIAVI’s Secure µPNT STL-1000 receiver module into Ground Control’s RockFLEET Assured maritime tracking and navigation platform, targeting vessels operating in GNSS-denied or contested environments.

The Secure µPNT STL-1000 is a compact, software-defined receiver that operates through VIAVI’s SecureTime altGNSS LEO service tier rather than relying on GPS/GNSS constellations. The module delivers precise timing with holdover capability — meaning it can maintain synchronization through signal outages — and is designed for what the defense sector terms Denied, Degraded, and Disrupted Space Operational Environments, or D3SOE. Its integration into RockFLEET Assured provides a secondary, independent position source alongside or in lieu of conventional GNSS, with the stated aim of sustaining navigation and vessel oversight when primary signals are jammed, spoofed, or otherwise unavailable.

“With jamming and spoofing now a core element of cyber warfare, resilient PNT solutions are no longer optional,” said Doug Russell, Senior Vice President and General Manager, Aerospace and Defense, at VIAVI. “Its compact size and low power consumption makes it ideal for applications that require an extremely small, low-power, secure, resilient embedded PNT receiver.”

Alastair MacLeod, CEO of Ground Control, framed the integration in terms of both commercial and defense exposure. “As the frequency of jamming and spoofing continues to rise, reliance on GPS/GNSS signals alone increasingly exposes both commercial and military operations to risk,” he said. “Integrating VIAVI’s Secure µPNT STL-1000 into RockFLEET Assured delivers a trusted secondary position source, strengthening resilience for mission-critical operations across defense, maritime and critical infrastructure environments.”

RockFLEET Assured is described as a marine-grade Assured PNT (A-PNT) solution. VIAVI, headquartered in Chandler, Arizona, and traded on Nasdaq as VIAV, positions itself as a provider of test, measurement, and optical technologies across defense, aerospace, and communications infrastructure markets.

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The Munich Space Summit remains one of the premier gatherings on the European space calendar, showcasing the accomplishments of leading industry players and policymakers. The Americans show up, too.

Despite current geopolitical strains, Europeans and Americans in the PNT and space communities continue to meet as collaborators, colleagues and, in many cases, longstanding friends. Conferences such as the Munich Space Summit are stronger for that transatlantic exchange.

One of the event’s key sessions, featuring program updates from the major satellite navigation providers, was moderated by Richard Fischer, publisher at U.S.-based Autonomous Media, the company behind Inside GNSS, Inside Unmanned Systems, Inside Autonomous Vehicles and xyHt.

“What strikes me most this year,” Fischer said, “is that the conversation around GNSS has clearly moved beyond constellation updates alone. Across the community, there is growing recognition that GNSS is critical infrastructure. It is no longer enough to think only in terms of accuracy and coverage. The language now is resilience, trust, authentication, continuity and assurance.”

Among the most anticipated appearances at the Summit was that of Christopher Erickson, the new U.S. Department of Transportation Director of PNT and Spectrum Management, succeeding longtime and widely respected GPS leader Karen Van Dyke. Erickson offered a sweeping overview of the current state of GPS, underscoring the extent to which U.S. positioning, navigation and timing (PNT) policy now involves a broad cross-section of government.

“It is very much a whole-of-government effort,” Erickson said. “NASA is addressing navigation beyond GEO and into the cislunar domain, developing plans for how position, navigation and timing will be provided in those environments. At the Department of Transportation, my office works across all transportation modes, including rail, highways and maritime, while the Federal Aviation Administration, of course, plays a central role in aviation. The Department of State is responsible for many of our international engagements with other global navigation satellite system providers, and the GPS system itself resides within the Department of Defense.”

It was the kind of summary that reminded the audience that GPS is no longer merely a satellite constellation, if indeed it ever was. It is a governance framework, a modernization program, a diplomatic instrument, a military capability, a civil utility and, increasingly, a resilience problem set. Erickson’s remarks made clear that no single office can now speak for the totality of the U.S. effort in PNT resilience. 

His overview continued in similar depth, and audience members received a concise but revealing tour of how GPS modernization, resilience planning and civil policy are being approached in Washington. Erickson was sharp, direct and notably comfortable speaking without presentation slides.

Off the Cuff

“One reason I did not feel it was essential to bring slides,” Erickson said, “is that GPS is, by design, a very deliberate and carefully managed system. If you have seen a GPS update in the last 18 months, you have likely seen many of the core elements already. That reflects our emphasis on stability, integrity and accuracy. We are cautious about implementing changes until we fully understand their implications.”

That observation may have drawn a few smiles, but it also underscored something important about GPS modernization: Progress in this domain is rarely theatrical. It is measured, highly scrutinized and often slower than outside observers would prefer. Yet, that caution is not accidental. It is built into the culture of a system on which aviation, defense, mapping, timing and countless commercial applications depend.

He then turned to the future of the constellation and the question of what comes after GPS IIIF.

“There are several avenues under consideration,” Erickson said. “We conducted a study known as R-GPS, or Resilient GPS, to examine how we might evolve the system while taking advantage of new capabilities and new thinking. That included looking at smaller satellites, shorter design lives, opportunities for multi-manifest launch, and ways to make the overall architecture less of a large, slow-moving enterprise and more agile, flexible and responsive, while preserving the accuracy and integrity on which users depend.”

He suggested a future architecture may not require every satellite to carry the same full set of functions.

“We also examined whether every satellite in a future architecture would need to carry the same full suite of capabilities,” he said. “If not, how might we distribute functions more effectively? How could space-based assets be used to complement one another? And how should such capabilities be distributed across orbit to deliver the most resilient and effective system?”

GPS may be deliberate in its evolution, but the strategic thinking around it is anything but static.

“We concluded that our primary focus should remain on MEO,” Erickson said. “At the same time, we launched the NTS-3 experiment, the first end-to-end navigation satellite experiment conducted by the United States in several decades. NTS-3 is exploring reprogrammability, ground responsiveness, user equipment implications, additional authorized signals, commercially relevant encryption approaches, and broader options for resilience. We hope to have initial results from that work later this year.”

Erickson also pointed to the Department of Transportation’s evaluation of complementary PNT technologies, an area of growing interest as governments seek to reduce overdependence on any single source of timing and navigation.

“We are close to releasing our first report covering approximately seven complementary PNT technologies,” he said, “and we are preparing to begin evaluating an additional group. In these efforts, we are procuring services from the companies involved and then assessing the technologies rigorously, from multiple operational and technical perspectives. The goal is to identify what these systems can do, where they perform well and where they may be appropriate within a broader PNT architecture.”

That is one of the most closely watched areas in U.S. policy today. The question is no longer whether alternatives or complements to GNSS exist. It is how they should be tested, how they should be compared and, most important, where they fit in a real operational framework. Erickson’s description suggested a government trying to move beyond abstract interest toward structured evaluation.

Another area gaining importance is PNT situational awareness.

“We have also begun a cross-government effort to create a shared data library,” Erickson said. “We already have several visualization tools and are continuing to expand and refine them. At the same time, we are engaging with international partners to share data and explore how to produce more comprehensive situational awareness products that can help inform decision-making as the interference environment evolves.”

Fischer then took the discussion in a broader direction, asking Erickson how the United States is thinking about the balance between maintaining an open global GNSS service and addressing the very real security concerns now moving to the top of the European agenda.

“If you are providing an open service,” Erickson said, “there are limits to what can be delivered solely by the service provider, and a significant portion of resilience necessarily resides with users and user equipment. That said, one important area I did not touch on earlier is authentication. It was not built into the civil service at the outset, largely because the scope of GPS’s eventual adoption was not fully anticipated. Today, however, we are working on out-of-band civil signal authentication that will be available to receivers with internet connectivity, and we are also advancing modernized civil authentication. Those efforts are proceeding in coordination with the U.S. Space Force as requirements are finalized and implementation moves forward.”

Forward with L5, but When?

The L5 signal is one of the most important modernization steps in GPS. More than simply an additional frequency, it represents a major advance in robustness, reliability and performance for safety-critical and precision applications. For aviation, surveying and other demanding user communities, L5 promises higher transmitted power, a stronger signal structure and characteristics specifically aligned with safety-of-life applications. First transmitted in 2005, however, it still has not been declared fully available for open-service users.

“We certainly have enough satellites on orbit transmitting L5 to support an initial capability,” Erickson said in response to an audience question. “By the time the tenth GPS III satellite is in the constellation, we expect to have 21. However, that is not the entire picture. The U.S. government has faced considerable pressure to declare the signal healthy, including under conditional approaches. But because L5 occupies a safety-of-life band, and because of what that means for our obligations with respect to integrity, we are not yet fully comfortable with the state of the overall enterprise.”

He made clear that the issue is tied not just to space assets, but to the ground segment and broader operational readiness.

“It is closely tied to the development of the ground system,” he said. “While I cannot provide a date today, we are continually reevaluating the situation and working toward bringing L5 forward as soon as we can do so responsibly.”

That answer led naturally to the larger issue of resilient PNT and the current U.S. posture.

“But stepping back to R-GPS,” Fischer asked, “what did the effort clarify, and how is the United States now thinking about resilient PNT more broadly?”

“That is an important question,” Erickson replied. “What you are seeing from the United States is an exploration of the boundary between what government should appropriately provide as foundational infrastructure and where the commercial sector should take the lead. The current administration has a strong interest in leveraging commercial capability wherever that is practical and effective.”

The question has resonance beyond the United States. When the European Union announced Galileo’s free High Accuracy Service, some commercial correction-service providers raised concerns that a government-backed free offering might disrupt existing markets. Ultimately, the market adapted, but the debate over where public provision should end and commercial opportunity should begin remains an active one.

“We are still working to define that appropriate boundary,” Erickson said, “what government should provide and what commercial industry is best positioned to provide in the context of resilient position, navigation and timing. I expect that this will eventually lead to a restructuring of broader PNT strategy. At present, however, we are in a data-collection and evaluation phase. NTS-3 is part of that. Our complementary PNT assessment effort is part of that as well. We are gathering the information needed to shape a coherent U.S. approach to resilient PNT moving forward, and I think we will see that picture come into much sharper focus over the next one to two years.”

The Timing’s Right

Timing, the “T” in PNT, is often overshadowed by navigation and positioning. Yet, it underpins telecom networks, power grids, financial systems and the digital infrastructure of modern life. Without precise timing, positioning solutions degrade, communications networks fall out of sync and critical infrastructure can quickly become unreliable. In Munich, timing was not overlooked.

Dana Goward, president of the Virginia-based Resilient Navigation and Timing Foundation, moderated a special Summit session on resilient time provision as a foundation of modern infrastructure. A longtime friend and collaborator of Inside GNSS, Goward is a familiar and respected figure in the transatlantic PNT community.

We caught up with him between sessions, where he explained the strategic framework he and others have been advancing.

“Timing is, and historically has been, a sovereign responsibility in support of both economic strength and national security,” Goward said. “At the RNT Foundation, and in some respects at the U.S. Department of Transportation as well, we have described a minimum resilient PNT architecture that includes what we call the resilience triad: signals from space, signals from terrestrial broadcast systems, and terrestrial fiber-based timing.”

The panel reflected that framework. Participants included Per Olof Hedekvist of Sweden’s RISE Research Institutes, an advocate for terrestrial backup systems such as eLoran; Stefan Baumann of IABG, who is active in resilient PNT testing, evaluation and system integration; Lisa Wörner of DLR, whose work includes resilient timing research, GNSS interference mitigation and alternative timing sources; and Tyler Reid, co-founder and CTO of Xona Space Systems.

Goward’s broader mission is to help policymakers understand the problem is solvable—and the tools to address it are already available.

“We have the technology, and in most cases it is not prohibitively expensive,” he said. “In many instances, elements of the solution are already in operation. What is needed is to bring them together coherently. At that point, the issue becomes one of leadership and governance.”

It is a message he has repeated often, and deliberately.

“We like to think of our work not as repetitive,” he said, “but as consistent. Staying on message matters.”

Storming Back

Another familiar and respected presence at the Munich Summit was Harold “Stormy” Martin, Director of the U.S. National Coordination Office for Space-Based PNT. As always, he offered pointed observations on the state of policy and implementation in the United States.

“We are in a relatively strong position in the sense that the policy guidance is clear,” Martin said. “Space Policy Directive-7, which was issued at the end of President Trump’s first term, speaks directly to resilience. Executive Order 13905 likewise calls on departments and agencies to strengthen resilience. So, the direction from the top-level policy framework is well established.”

By any measure, GPS remains one of the most consequential—and in some ways unexpected—success stories in modern infrastructure.

“There was never a plan for GPS to become the sole source of timing and navigation for federal departments or for critical infrastructure,” Martin said. “That does not appear in any White House policy document. Rather, we are in some respects dealing with the consequences of GPS’s extraordinary success. GPS and other GNSS services have been reliable, widely available and increasingly inexpensive to use. Receiver costs have fallen dramatically, and that has made GNSS the simplest choice for many budget-conscious decision-makers. Over time, alternative systems were reduced or eliminated, and some sectors now find themselves reliant on GNSS as their only remaining source of navigation and timing.”

That reality, he said, has created a strategic vulnerability that policymakers are now trying to address.

“It is an excellent system, and it has served us extremely well,” Martin said. “But every system has vulnerabilities. The signal originates roughly 12,000 miles away in space. It can be jammed. It can be spoofed. Those are not hypothetical issues.”

Current policy, he noted, places the emphasis on resilience, but implementation is inseparable from budget realities.

“Our policies are clear in telling organizations that they need to become more resilient,” Martin said. “The challenge, of course, is that these efforts remain subject to appropriations, and funding can be difficult to secure. Part of what we are trying to do is educate new decision-makers and create incentives for investment. You can already see some early steps in that direction. The FCC has issued a Notice of Inquiry on complementary PNT. That is part of building the record around what can be done to encourage industry to provide complementary PNT technologies that, together with GPS, can support a resilient and secure national PNT system of systems.”

How urgent is the issue? Martin suggested that current events are making the case more effectively than any abstract policy argument could.

“There is an old saying in Washington: Never let a good crisis go to waste,” Martin said. “If you look at the levels of jamming associated with conflicts in the Red Sea, in the Russia-Ukraine war and elsewhere, it becomes much easier to show leaders that this is not a theoretical concern. The objective is to strengthen our systems before that kind of disruption has domestic consequences.”

Getting Answers

A central part of the federal government’s effort to understand GPS vulnerability and evaluate alternatives has been the work conducted through the U.S. Department of Transportation’s Volpe Center. The so-called Volpe study has examined weaknesses in GPS-dependent operations while assessing candidate backup and complementary PNT technologies.

“Testing is essential,” Martin said. “And when we talk about mature technology, that includes practical readiness. One benchmark is whether a provider can bring equipment to a test site within six months. That is the kind of criterion that helps distinguish conceptual promise from deployable capability.”

The testing program is ongoing, and some reports are expected soon.

“The good news is that this is an achievable problem set,” Martin said. “We have policy guidance. We have demonstrated that credible technologies exist. The next step is determining how to invest. I have been making that case for 10 years, and I am more encouraged now than I have been in a long time.”

That closing note of cautious optimism matched the mood in Munich. The technical problems remain substantial. The policy questions are far from fully resolved. The funding picture is still uncertain. Yet, there is now a stronger shared vocabulary around resilience, a clearer understanding of the stakes and, perhaps most important, less hesitation about acknowledging that dependence on GNSS alone is no longer sufficient.

As temperatures outside dropped and snow began to fall over the Bavarian capital, the atmosphere inside the Summit remained warm and energetic, animated in no small part by speakers such as Erickson and Martin, and by the wider community now working to define what a resilient PNT future should look like. The concerns are real, the systems are under pressure and the architecture of the next phase is still being worked out. But in Munich, the conversation felt notably more mature than it did even a few years ago.

That, in itself, was one of the stronger signals to come out of the Summit.

And when this issue of Inside GNSS is presented at the Assured PNT Summit in Washington on April 7, it is likely that many of the same themes will be waiting there: resilience, authentication, complementary systems, timing assurance and the growing recognition that PNT must now be treated not simply as a technical service, but as strategic infrastructure. 

Munich did not resolve those questions. But it did provide a clear and timely snapshot of how seriously they are now being taken on both sides of the Atlantic. 

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