PANOSETI — Pulsed All-sky Near-infrared Optical SETI — is a multi-institutional program led by researchers at the University of California, Berkeley. The system requires extremely precise time coordination across widely separated telescope nodes to detect fast-transient optical and near-infrared signals. Traditionally that level of synchronization has depended on fiber-based infrastructure such as White Rabbit, which is costly and impractical to deploy at remote observatory sites.

Using the u-blox ZED-F9T, the PANOSETI team demonstrated approximately 0.7 nanosecond standard deviation between 1PPS signals over a 1-kilometer baseline, with performance improving to around 200 picoseconds using filtering techniques — meeting or exceeding the requirements for next-generation distributed sensing systems.

“Achieving this level of synchronization without fiber is a significant step forward for distributed instrumentation,” said Dan Werthimer, Chief Scientist of the PANOSETI project at UC Berkeley. “It allows us to achieve the timing precision we need for our telescope array in locations where traditional fiber-based systems are not feasible.”

The u-blox announcement frames the result as extending beyond scientific research, pointing to applications in distributed sensor networks, remote timing systems, and resilience of critical infrastructure.

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The milestone centers on Qualinx’s QLX3xx — a reconfigurable GNSS SoC and Analog Front End targeting secure positioning, navigation, and timing applications, including resilient timing and synchronization networks and ultra-low-power GNSS receivers for connected edge deployments. The chip was designed, taped out, and manufactured entirely at GF’s Dresden fab using its FDX process technology. No design data or physical materials left the European Union at any stage of production.

“Our partnership with Qualinx marks the first operational milestone,” said Dr. Manfred Horstmann, SVP and General Manager at GF. “It shows that complex, security-relevant ASIC designs for aerospace, defense, and critical infrastructure can already be industrialized today using a fully European, trusted manufacturing path.”

Qualinx CEO Tom Trill characterized the flow as proof that full European manufacturing control is no longer theoretical. “This first secure product demonstrates that a fully European manufacturing path — from mask services to wafer production — is already a reality today,” he said, adding that the effort gives Qualinx complete control over IP, data, and supply chain within Europe.

The Dresden fab’s sovereign manufacturing capability is co-funded under the European Chips Act. GF says it aims to have a fully automated trusted European flow in place by end of 2026, with regular foundry engagements available to aerospace and defense customers starting in 2027. That roadmap will incorporate European IP partners, mask houses, and OSAT service providers.

GF is also working with Deutsche Telekom on a parallel effort to ensure that production data — from design and tape-out through manufacturing and quality — can be processed, transported, and stored entirely on European networks, cloud infrastructure, and data centers. The practices developed there are intended to feed directly into the scaling of the sovereign manufacturing model.

Qualinx, headquartered in Delft, Netherlands, was founded in 2015. The company’s proprietary Digital Radio Frequency technology implements traditional analog receive-chain functions in digital hardware, targeting GNSS, PNT, and PVT chipsets and modules for applications ranging from automotive and fleet to wearables and asset tracking.

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It’s late at night, January 29, 2026. Most of Southern California is asleep. Ships approaching Long Beach harbor from the West key their mics on VHF channel 14 and report GNSS outages to LA/Long Beach Vessel Traffic Service (VTIS). Aircraft over the Channel Islands squawk the same via ADS-B. NOAA Continuously Operating Reference Station (CORS) sites record anomalies in L1 and L2 signal-to-noise ratios. All of this within an hour.  

While spoofing and jamming of GNSS have been recurring issues in conflict zones, incidents like this show no one is immune. 

Maritime Impacts

Automatic Identification System (AIS) reports from at least 7 vessels indicate position jumps indicative of spoofing. At least one vessel’s AIS system ceased transmitting altogether for nearly an hour, likely due to an invalid GNSS solution. Data indicates this event covered greater than a 100-mile area, including the critical LA/Long Beach Traffic Separation Scheme. 

All of the documented GNSS anomalies occurred within one hour, but the most dramatic position jumps shown by AIS messages lasted only several minutes. The short duration of the event is the only factor that prevented greater impact on PNT and limited public awareness of the event.

All of the reported interference occurred between 11 p.m. and midnight local time, with good visibility and no inclement weather, and all the vessels involved entered port without incident.  But, it should be noted that several of the vessels were navigating in close proximity to one another in the vessel traffic separation scheme, and loss of valid GNSS solution could impact situational awareness and create distraction at a critical point in their voyages.

Figure 2 shows the AIS track of a large container ship showing position jumps resulting in invalid, erratic course and speed over ground:

A tanker experienced similar position jumps:

In addition to AIS vessel reports, which typically are transmitted at about 10 second intervals while underway, three local NOAA CORS sites recorded Signal-to-Noise Ratio (SNR) anomalies in the same hour:

Figure 4 

Aviation Affected

Additionally, the GPSjam.org website showed aircraft evidence (ADS-B messages) of GNSS anomalies much further to the southwest of the reporting commercial ships, indicating the interference may have covered a far larger area than AIS data indicates. 

Figure 5 

The Source

On February 4, six days after the event, the minutes of the L.A./Long Beach Harbor Safety Committee meeting recorded:

“GPS Outages: On the evening of January 29, VTS LA-LB received multiple reports of GPS outages from vessels in the LA-LB AOR. Sector personnel, with support from our port partners and the Coast Guard Navigation Center, were able to identify a GPS testing event as the likely cause. While there were no incidents or negative impacts due to the outages, the Coast Guard continues to investigate the outages and will take action to prevent recurrence.”

While GPS testing is a regular occurrence, interference like that of Jan 29, 2026, is quite rare.  

The available data does not provide certainty, but the most likely source of these anomalies was a GPS test dubbed PMSRCA 26-02, that is, Point Mugu Sea Range California 26-02.  

An FAA Notices to Airmen (NOTAMs) released on January 22, 2026. states: 

“GPS testing is scheduled as follows and may result in unreliable or unavailable GPS signal.”

A. Centered at 332451N1183430W or the SXC VOR 272-degree radial at 8 NM. 

                                        (near Catalina Island)

B. Dates and times (Dates and times are based on GMT (Z).): 

27 – 31 JAN 26 DLY 0700Z – 1400Z  (event occurred 30 Jan 0700Z – 0800Z)

D. NOTAM INFO: NAV GPS (PMSRCA GPS 26-02) (INCLUDING WAAS, GBAS, AND ADS-B) MAY NOT BE AVBL WI A 452NM RADIUS CENTERED AT 332451N1183430W (SXC272008) FL400-UNL, 

                   …and included this graphic (Figure 6):

While NOTAMs alert aviation, the U.S. Coast Guard Navigation Center (NAVCEN) website publishes monthly schedules of GPS testing for mariners. However, PMSRCA 26-02 was not listed on the January schedule, but did appear on the February GPS testing schedule released on February 13, 2026, about two weeks after the January 29 jamming and spoofing instances.

Even though the NAVCEN website may not have published notification of that particular GPS test in a timely manner, GPS anomalies are so infrequent in the Americas that few mariners would likely have been alerted. The unfortunate reality is the United States, unlike China, Russia, South Korea, the United Kingdom, Saudi Arabia and India, has not established a viable alternate PNT system.  

When GPS/GNSS is unreliable or unavailable, AIS goes down with it, or, even worse, will transmit and receive spoofed position, courses and speeds. Until an alternative PNT system to backup GNSS is a reality, the only option is to defend GNSS against jamming and spoofing. There are technologies with such capabilities, but they have yet to be embraced by the shipping industry.  That risk-reward calculation may change if GNSS reliability continues to erode not only in conflict zones, but other parts of the globe as well. We may be entering new frontiers in electronic warfare as recent reports of space-based interference could raise the stakes for PNT users across the globe.

Authors 

Captain James Haley is a senior consultant for UHU Technologies. He served for 32 years as a harbor pilot and navigation technology expert in Long Beach, Calif.

Captain Dana A. Goward is President of the Resilient Navigation and Timing Foundation. He retired from the Senior Executive Service and served as the maritime navigation authority for the U.S.

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Cold War shortwave numbers stations broadcast strings of digits to anonymous listeners, content that’s meaningless to anyone without a matching one-time pad. They still operate today.

As it turns out, GPS broadcasts in much the same way.

Buried in every L1 C/A navigation message is Subframe 4, Page 17—a 176-bit field that IS-GPS-200 reserves for “special messages with the specific contents at the discretion of the Operating Command.” Every satellite broadcasts it. Every receiver decodes the subframe that contains it. And for nearly two decades, no one has publicly explained what it contains.

We analyzed 12.16 million observations in this field from 2007 through early 2026. The content is not text. It is encrypted material consistent with the military’s Over-the-Air Distribution (OTAD) global rekeying network. For 19 years, every operational GPS satellite has been a numbers station—broadcasting ciphertext on a public channel, to billions of receivers, in plain sight.

If you build receivers, write firmware, run signal monitoring, or care about the gap between civil and military signal transparency, this is your field too. You just have not been reading it.

What follows is the story of how a forgotten 176-bit slot in the world’s most successful navigation signal turned out to be its quietest and most consequential broadcast—and how a few weeks of analysis on a laptop, applied to 19 years of public archive data, was enough to read its operational history off the bytes.

176 Bits, Eight Words, One Forgotten Page

The L1 C/A signal carries 50 bits per second. Every bit must earn its place. The Legacy Navigation message organizes those bits into 1,500-bit frames, each frame into five 300-bit subframes, each subframe into ten 30-bit words. Subframes 1 to 3 carry the heavy work—clock corrections, ephemeris, the data your receiver needs every few seconds. Subframes 4 and 5 multiplex 25 rotating pages. A receiver sees Page 17 of Subframe 4 every 12.5 minutes.

Across 32 satellites, that is roughly 3,700 special-message payloads per day, fleet-wide. Multiplied across 19 years and the global ground-station archive, the figure climbs to 12.16 million observations.

176 bits is barely enough for a few floating-point numbers, but in a 50 bps signal, it is roughly 12% of every Subframe 4 broadcast. For the control segment to use that bandwidth consistently for two decades implies the content matters—even if no civilian receiver has ever rendered it.

Figure 1 shows how the bits are arranged. The 176-bit payload is fragmented across Words 3 to 10 of Subframe 4, Page 17: 16 data bits in Word 3 (after eight bits of Data ID and SV ID = 55, the marker that identifies Page 17), 24 data bits in each of Words 4 to 9, and 16 data bits in Word 10. The final six bits of every word carry the parity bits. After parity stripping and reassembly, the 22 bytes of payload are decoded under a subset of Code Page 437.

Mining 19 Years of Navbits

The corpus comes from the GFZ Potsdam open archive GNSS recordings collected from a wide network of ground stations, dating back to 2007. After extraction, the numbers settle: 12.16 million observations of Subframe 4, Page 17, drawn from every operational PRN, spanning 19 years, yielding 3,994 unique 176-bit messages.

Initial Python implementations needed hours to process a single year. To make iterative analysis practical, we wrote a Julia pipeline: NetCDF source files are converted to Apache Arrow, then thread-parallel bit extraction is performed into a DuckDB database. The full 19-year corpus extracts in seconds on a laptop. SQL across the lot returns in milliseconds.

With 12.16 million payloads in a queryable database, the question becomes: What does this field actually contain?

It Is Not Text. It Never Was.

The first thing a researcher tries in an unknown field is the obvious one: maybe it is text in a different encoding. We computed the frequency of each of the 45 alphabet symbols defined by IS-GPS-200 across all 12.16 million observations. In English, frequencies have a fingerprint—E and T are common, J and Z are rare, spaces and full stops are more common than digits. In a uniform random stream, each of the 45 symbols should appear with probability one in 45—about 2.22%.

The observed frequencies tracked the uniform baseline with remarkable precision. A chi-squared test against uniform yielded a z-score of 1.84, well inside the range where we cannot reject the null hypothesis of randomness. Across 12.16 million observations, the distribution is statistically indistinguishable from random data.

A stronger test asks the same question from a compression angle: How much information does each unique message contribute, given the others? An order-8 PPM-D compression model trained on the full corpus measures the marginal entropy of each payload—the additional cost, in bits, of encoding that message given everything else the model has seen. Real text would compress: Any recurring phrase, formatting block, or repeated formula would become almost free to code. Random data would not. Figure 2 plots the resulting distribution alongside a synthetic random baseline of 3,994 messages drawn uniformly from the 45-symbol alphabet and scored against the same model. The two distributions overlap almost perfectly, with means within half a bit of each other. By every available statistical lens, the GPS messages are almost indistinguishable from random, but there are intriguing outliers. At the lower end, messages are much more predictable than you would expect from random data; at the higher end, sentinels stand out from the rest. 

In Figure 2, blue indicates the marginal coding cost of each of the 3,994 unique 22-byte payloads under an order-8 PPM-D model trained on the corpus (μ≈131.5 bits per message≈6.0 bits per byte, σ≈7.6). Red indicates the same model scored against a synthetic baseline of 3,994 messages drawn uniformly from the 45-symbol GPS alphabet (μ≈132.0 bits, σ≈3.8). The two distributions overlap almost perfectly—the GPS messages are indistinguishable from random under the model. 

The next issue is that high-entropy output can come from encryption, compression or genuine randomness, and entropy alone cannot tell us which. This is correct. It is also the entry point to the rest of the article. If the field is encrypted, the protocol shape may still leave traces—placeholders where no payload is loaded, regime changes where policy shifts. In these structural metadata, the cipher does not reach. Encryption doesn’t hide “traffic data” of when and how often messages are sent and from which satellites. Each of those is a crack in the randomness, and the rest of this story walks through them in order.

What the entropy result does close off is the comfortable interpretation. Between 2007 and late 2023, no readable English appears anywhere in the dataset. No call signs, no acknowledgments, no test patterns of “the quick brown fox” variety. The field has not carried text in any conventional sense for the entire archived history of the GPS constellation.

For an engineer, that absence is itself information. The interface specification says this field is for text from the control segment. The bytes flatly disagree, and they have done so consistently, across every satellite, for 19 years.

High entropy on its own tells us only what the field is not. To learn what it is, we had to look for the cracks in the randomness.

A Single Byte, Repeated 22 Times, for 10 Years

The first crack in the randomness is also the most visible. Three messages, out of 3,994, have Shannon entropy of exactly zero. They are sentinels: 22 consecutive identical bytes broadcast as a single repeating pattern across the full payload.

• All-spaces—22 of byte 0x20.

• All-NUL—22 of byte 0x00.

• All-¬—22 of byte 0xAA, the CP437 negation glyph.

The all-¬ pattern is the longest-lived artifact in the dataset. It first appears on PRN 25 in February 2010, and quickly becomes the dominant default for the constellation, persisting intermittently across all 32 satellites for more than a decade.

The choice of byte 0xAA is not accidental. In binary, it is the perfectly alternating bit pattern 10101010—the canonical test sequence for bit synchronization, parity verification, and frame-alignment checks in receiver hardware. A satellite broadcasting all-¬ is broadcasting the protocol equivalent of a tone: present, parseable and intentionally empty. It is also outside of the characters permitted in the special message field, causing receivers to flag up data validation errors.

That intentionality matters. Encryption alone does not produce a constant. A genuinely random stream visits all-0xAA with negligible probability. The sentinels are placeholders by design—slots in the protocol marked as “no operational payload loaded.”

Their behavior fits that reading. Cross-referencing with GPS status reports (Notice Advisory to Navstar Users—NANU) shows satellites often enter sentinel states during commissioning and decommissioning. PRN 25 itself is the textbook case. The Block IIA satellite using that slot was decommissioned in December 2009. By February 2010, the slot was broadcasting all-¬. Its replacement, the first Block IIF, launched in May 2010, began pre-commissioning tests in August and also broadcast the all-¬ sentinel for several days before being declared fully operational on August 27. The pattern is unambiguous: When no operational payload is loaded, the field broadcasts the sentinel.

In a corpus where messages are replaced and never repeated, the sentinels are the only payloads that recur. Every other unique 176-bit message in the dataset appears in fewer than two calendar months for any given PRN. The sentinels persist for years. So, messages are replaced, never repeated—except the sentinels.

Why a system would broadcast a no payload loaded placeholder at all, and to what kind of receiver, needs the operational context that the rest of this article rests on.

Why GPS Carries Encrypted Signals—and What That Costs to Run

GPS broadcasts more than the open civilian C/A code. Since the activation of Anti-Spoofing on January 31, 1994, the constellation has carried encrypted military signals on the same frequencies: the Y-Code (the encrypted form of the precision P-Code on L1 and L2) and, on modernized satellites, the newer M-Code introduced with the GPS IIR-M block from 2005 onwards. These signals provide authorized receivers with jamming and spoofing resistance that civilian users do not have. The separation between open and encrypted signals also allows the operator to degrade the accuracy of civilian receivers while maintaining the precision of authorized ones. 

Encrypted signals need keys. Authorized receivers built since the late 1990s integrate a tamper-resistant cryptographic module called the Selective Availability Anti-Spoofing Module (SAASM)—the cryptographic basis of in-service infantry units such as the Defense Advanced GPS Receiver (DAGR). The SAASM holds a cryptographic key that lets the receiver lock onto the encrypted signal; without a current key, the receiver falls back to the unencrypted C/A code that anyone can track.

Keys do not sit still. To limit the damage from any single compromise, operational keys rotate on a schedule that, depending on the key class, can be as short as a single day. Every receiver in service—and the U.S. military operates them in the hundreds of thousands, across every theatre, vehicle platform, weapon system, and aircraft—needs each new key before its current one expires.

For most of GPS’s history, that meant physical key-fill: specialized loader devices had to be carried to each receiver, plugged in, and used to push the new key into the SAASM module. The keys themselves were distributed through NSA secure-courier channels. The logistics were demanding even in peacetime; in deployment, units that missed a key-fill window lost access to the encrypted signal until they could be reached again.

Over-the-Air Distribution (OTAD) and the closely related Over-the-Air Rekeying (OTAR) were the answer to that logistics problem. The principle is straightforward. A receiver that is powered on and already holds a valid current key can have its next key delivered via the GPS navigation message itself—encrypted under the current key and decoded within the SAASM module—without physical contact, a courier chain, or missed-window failures. The OTAD payload, the “next black key” in military parlance (where “black” denotes encrypted-at-rest), is what the GPS control segment must deliver to every authorized receiver on a schedule, via a public broadcast channel.

That delivery mechanism is what we believe Subframe 4, Page 17 has been carrying since at least 2007. If so, the constellation should reveal somewhere in its 19-year broadcast history the moment the delivery system went operational. And it does.

May 26, 2011: The Day the Constellation Spoke in Unison

May 26, 2011. Above the Earth, 31 active GPS satellites in 12-hour MEO orbits, each in its own slot, each broadcasting its own special message. By the end of the day, every one of them was broadcasting the same one.

Within a window of a few hours, all 31 operational satellites switched to the all-¬ sentinel. Every active PRN. Same payload. Same byte. Same coordinated event.

Figure 3 shows the 48-hour per-PRN timeline of the transition. It reads as a vertical bar slicing across the constellation: a step change so sharp and so simultaneous that no observational artifact can explain it. The data come from multiple receivers, ruling out a station-side glitch. Every PRN is involved, ruling out a single-satellite anomaly. No NANU was issued announcing a fleet-wide event of this kind.

In Figure 3, the Per-PRN broadcast state across a 48-hour window is centered on the transition. Each row corresponds to one of the 31 active GPS satellites; time runs from left to right in UTC. Within a few hours, every PRN switches to the all-¬ sentinel (red), holds it for between three and 24 hours, and exits to a new operational message at the end of the day. No publicly recorded NANU announces a fleet-wide event of this kind in the surrounding window. The transition coincides with the operational activation of the U.S. Over-the-Air Distribution rekeying network.

What remains is a coordinated, control-segment-driven blanking of the field across the entire operational constellation—the kind of thing that happens once, when an underlying system goes operational.

Declassified documentation places such a milestone in this exact period. A 2015 briefing by Maj Scott Tyley of the Space and Missile Systems Center describes the operational rollout of the U.S. OTAD system and its companion OTAR. The briefing identifies March 2011 as the start of continuous operational U.S. OTAD on all space vehicles.

Temporal alignment is not enough on its own to prove the connection; operational systems achieve operational status every year, and most of them do not announce themselves on L1 C/A. What raises the alignment from coincidence to causation is what happened next.

In the pre-OTAD era of 2007 to 2010, the constellation rotated unique payloads on average every 3.4 days; the 2007 to 2008 sub-period averaged about 2.3 days. In the operational era of 2012 to 2021, that rate jumped to once every 0.9 days, with a median message duration of 23 hours—almost exactly once a day. The H1 2011 period itself shows a cascade of four coordinated change points (January, February, May, June) culminating in the May 26 fleet flash, consistent with a phased activation rather than a single instantaneous transition. The result is consistent with the field being switched from a pre-operational test mode to an automated daily key-distribution cadence—exactly the operational tempo OTAD requires to deliver “next black keys” to SAASM-equipped receivers in the field.

Within a single 24-hour window, every operational GPS satellite switched to the same value.

From One Message a Week to One a Day, and Back Again

The 2011 flash drew a line through the dataset. Looking across the full 19 years, the field exhibits three behavioral regimes, each separated by a coordinated change point detected by Cumulative Sum (CUSUM) analysis applied to per-PRN message rotation rates.

The Pre-Operational Era, 2007 to 2011: A new payload per satellite roughly every 3.7 days on average. The rotation is irregular, the diversity is low, and the sentinel fractions are high. The pattern is consistent with field testing, including the 2010 coalition key transition exercises described in Tyley’s briefing. The system existed but was not yet running at operational tempo, or perhaps a predecessor system was in operation.

The Operational Era, 2011 to 2022: A new payload per satellite roughly every 1.8 days, fleet-wide, with median per-message duration of 23 hours. Daily cadence is the lifetime of a tactical cryptographic key; daily replacement of the field’s content is the operational signature of automated key distribution. The sentinels recede into the background; unique payloads dominate, with 162 to 381 distinct messages per year. For 11 years, the GPS constellation has operated the most widely used automated rekeying network on Earth.

The Modern Era, 2022 to Present: In May 2022, there is a sharp coordinated change point. The rotation rate drops to one payload every 4.3 days at the regime boundary, then keeps slowing. By 2025, it is approximately one payload per 6 days, and by early 2026 it is closer to one per 6.8. The shift is fleet-wide, simultaneous across 17 to 32 satellites, depending on which metric is examined, and again unaccompanied by a publicly recorded NANU.

Three rates: 3.7, 1.8, 4.3+ days per payload (the third era’s rate is not stable and has continued to slow). Three regimes: pre-operational, operational, post-2022. Figure 4 shows them as three plateaus separated by sharp coordinated transitions.

The fleet-mean per-message duration in days is plotted across the full 19 years of the corpus in Figure 4. The pre-OTAD era (2007 to 2010) cycles roughly every 3.7 days. From May 2011 the rotation accelerates to one payload every 1.8 days, sustained for 11 years and consistent with daily tactical key distribution. In May 2022, a coordinated change point detected by CUSUM analysis reverses the trend on roughly 30 satellites simultaneously; rotation slows to 4.3 days per payload at the boundary and continues to slow within the era — to 6.8 days by early 2026. Vertical lines mark coordinated change points (≥ 8 PRNs within ± 3 days).

The 2022 reversion is the most interesting open question in the dataset. Several readings are consistent with the data, and none are conclusive.

It could mark the migration of OTAD traffic from L1 C/A to a different signal, most plausibly M-Code on L1/L2, where modernized military receivers have been operating since the GPS III deployments began.

It could reflect a change in cryptographic policy: longer key lifetimes, fewer rotations, more reliance on session-key derivation at the receiver.

It could be the first visible footprint of the recently terminated Next Generation Operational Control System (OCX) ground segment, whose deliberate, staged rollout was a public program for years.

What the data say definitively is that whatever the explanation, it was a single decision applied across the entire fleet at once, and the public record contains no notification of the kind we would expect.

A field that announces operational changes by the cadence of its own ciphertext is a field worth watching.

When Encrypted Messages Share Their Spelling

If the messages were genuinely random—random or properly encrypted with independent keys, padding, and initialization vectors—then no two unique payloads should share any meaningful structure. Each 176-bit message would be statistically independent of every other.

They are not.

A Prediction by Partial Matching (PPM-D) order-8 compression model, trained over the full 3,994-message corpus, identifies pairs and small groups of unique messages that share long, identical substrings at the same byte positions. Examples from the catalog:

• Two messages broadcast on October 8, 2014, share 10 identical characters in identical positions.

• A message from June 2021 and a message from September 2020 share a 9-character substring at the same offset.

• A pair of late-2019 messages, broadcast three weeks apart, share eight characters at identical byte positions.

• The substring LY47IRP16—9 bytes—appears in messages broadcast nine months apart.

• S°6L.D°—7 bytes—recurs three months apart.

The probability that any given pair of 22-character messages drawn independently from a 45-symbol alphabet would share a nine-character substring at the same offset by chance is negligible. Across the full corpus, the matches are not coincidental; they are structured. 

In Figure 5, five message pairs are identified by an order-8 PPM-D compression model as sharing long substrings at identical byte positions, despite being broadcast days, weeks or months apart. Each pair is shown one above the other, with shaded cells highlighting the matching bytes. The remainder of each message is the high-entropy ciphertext that fills almost the entire corpus.

The most likely explanation is protocol metadata leaking through. Every cryptographic transport protocol wraps its payload in headers—key identifiers, sequence numbers, etc. However, this alone is not a sufficient explanation because these values are encrypted and should therefore differ for every message. In addition to fixed metadata, there would need to be re-use of a key, whether due to operational error or exceptional circumstances. In such a scenario, we would expect to see partial matches between two different messages.

There is a practical consequence. If the substring matches are protocol metadata, they offer an external observer something the cryptography was meant to deny: a way to fingerprint and track individual key-distribution events from public signal data. A monitoring receiver, watching a small set of fixed byte positions across the entire constellation, could, in principle, detect when a particular key identifier or routing header is reused, retired or correlated with a NANU-announced operation. Cryptographically, the keys remain secure. Operationally, the metadata is loud.

In a stream that should be indistinguishable from noise, the protocol left a fingerprint.

The First Readable Bytes in 19 Years

In the corpus that runs from 2007 to mid-2023, no payload anywhere contains a recognizable word from any language that’s intended for direct human consumption. Then, on December 13, 2023, PRN 8 broadcasts a message that begins with the literal four-byte string TEXT.

After 16 years of pure ciphertext, the field has begun to use the format the standard always described. 

The migration is both staged and deliberate, reading like a deployment plan rather than just a casual flip of a switch.

• December 13, 2023—first appearance, on PRN 8 alone.

• March 18, 2024—the same TEXT-prefixed message broadcast on 10 PRNs simultaneously: a one-day fleet-wide distribution event.

• July 31, 2024—a second TEXT message, on PRN 3 alone.

• October 10, 2024—a four-PRN distribution.

• December 29, 2024—January 13, 2025—daily TEXT messages on PRN 1, with a different payload each day.

• March, June 2025—the daily-broadcast PRN moves to PRN 21.

• July–August 2025—the daily-broadcast PRN moves to PRN 20.

Each TEXT-prefixed message rotates daily and carries an 18-byte payload following the prefix. The payload itself remains high-entropy—by every statistical measure indistinguishable from the ciphertext that preceded it. The format has changed. The content shape has not.

The most plausible reading is a generational upgrade. OCX is rolling out. GPS III satellites are operational and growing as a fraction of the constellation. A new variant of OTAD, or a new auxiliary use of the field bolted alongside it, is being commissioned by PRN.

For receiver firmware, the migration matters in a way the previous 19 years did not. A field containing static-looking ciphertext is one that most parsers ignore. A field that apparently carries a structured type identifier followed by a payload must be parsed correctly.

The September 2020 SVN 74 anomaly is a cautionary tale, even though it concerns a different field: an ICD-defined alarm pattern transmitted as prescribed, with a minority of commercial receivers failing to handle it correctly and pushing bad positions to ADS-B users. The TEXT-prefix migration is an analogous situation—content that finally matches the special-message field’s standard format, arriving on receivers that may have spent two decades treating this field as static or ignored. Either direction of mismatch, content the standard did not describe, or content that suddenly does, can produce the same kind of outcome.

For the receiver and firmware teams, the practical action is short. Audit any code path that touches Subframe 4, Page 17. If the field is currently being skipped, logged as static, or assumed to be text, that assumption now has an expiration date. The TEXT prefix suggests the message is intended for human consumption; the trailing 18 bytes are the payload, which the standard has always permitted. Code that handles both is forward-compatible. Code that handles only one is the next September 2020 waiting to happen.

The migration is happening now. As of early 2026, only a handful of satellites have broadcast TEXT-prefixed messages, and the rest of the fleet continues to use the unstructured format. Which PRN converts next, and what its first TEXT-formatted message says, is the most accessible real-time measurement of GPS ground-segment evolution available to anyone with a receiver and patience.

Figure 6 plots every TEXT-prefix broadcast event in the corpus, satellite by satellite.

It shows 26 unique messages, 38 (PRN, day) combinations and 2,398 total observations. Marker size scales with daily observation count. Five distinct phases are visible. The first TEXT message appears on PRN 8 on December 13, 2023 (red). Three multi-PRN distribution events follow in 2024 (teal): a 10-PRN event on March 18, 2024, a single-PRN appearance on July 31, and a four-PRN distribution on October 10. From December 29, 2024, the protocol stabilizes into bursts of consecutive daily broadcasts that migrate between satellites: first PRN 1 (dark grey, December 2024 to January 2025), then PRN 21 (purple, March and June 2025), then PRN 20 (amber, July to August 2025). The migration looks far more like a staged deployment than an organic spread.

The Bottom of the Rabbit Hole, Or the Top of It

For nearly two decades, every operational GPS satellite has broadcast an encrypted stream consistent with the backbone of the U.S. military’s global cryptographic key distribution system.

The 2011 fleet flash was the constellation-wide synchronization that brought the system to operational capability. The 0xAA sentinel is the protocol’s no payload loaded marker. The shared substrings are the structural fingerprints of an OTAD frame leaking through the cipher. The 2022 reversion is the system in transition. The TEXT prefix is the system in renewal.

This matters in three ways:

• For signal authentication. OTAD is the proven, decades-long predecessor to civilian schemes like Galileo OSNMA and GPS CHIMERA. Its operational history, until now invisible, is data that the authentication community can study.

• For operational transparency. Both the 2011 flash and the 2022 reversion happened without the kind of public NANU record one might expect for a fleet-wide operational change. The methodology in this article, open archives, off-the-shelf tooling, 18k lines of Julia, gives the GNSS community the means to monitor the constellation’s internal states for itself.

• For pure engineering curiosity. Every receiver in the world decodes Subframe 4, Page 17. Almost none of them have ever looked at it. The lesson generalizes: There is more to learn from the bytes already arriving at our antennas than from the bytes we wish were specified differently.

The data are publicly available. The signal is overhead, twice a day, every day. We invite the GNSS engineering community to join the audit for L1 C/A and the newer signals that will inherit its role.

Every GPS satellite is a numbers station. The receivers were always listening. We just had not been. 

Acknowledgements 

This article is based on a project developed by Ahmed Kamruddin during his MSc studies at University College London. Thanks also to Ramsey Faragher and Markus Kuhn for valuable comments on this work. The initial stages of the work were performed within the Trusted Innovative GNSS receivER (TIGER) project, co-funded by the European GNSS Agency (GSA) under grant agreement 228443. Source code supporting this project can be found at https://doi.org/10.5281/zenodo.20073222.

Author

Steven J. Murdoch is Professor of Security Engineering, head of the Information Security Research Group and lead for the Foundational Computer Science section in University College London. His research encompasses payment system security, privacy enhancing technologies, online safety, and the intersection of computer science and law. He teaches on the UCL MSc in Information Security. He has worked with the OpenNet Initiative, investigating Internet censorship, and for the Tor Project, on improving the security and usability of the Tor anonymity system. His current research focuses on how computer systems can generate evidence to facilitate fair and efficient dispute resolution. He is a member of REPHRAIN, the National Research Centre on Privacy, Harm Reduction and Adversarial Influence Online and co-leads the CRANE NetworkPlus on Cybersecurity. He is a director of the Open Rights Group, a UK-based digital campaigning organization that works to protect rights to privacy and free speech online. He is also a Fellow of the IET and BCS.

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Murata had previously invested in Xona through WONDERSTONE Ventures, its corporate venture capital arm. The MOU moves the relationship downstream toward hardware, pairing Murata’s capabilities in high-frequency communications, sensors, timing devices and module design with Xona’s LEO-based PNT infrastructure.

Xona’s Pulsar service is built on a dedicated LEO constellation designed to deliver significantly stronger signals than conventional GNSS, with centimeter-level positioning accuracy, faster convergence times, reduced multipath error and improved performance in urban and indoor environments. Pulsar is designed for GNSS compatibility, enabling integration with existing user equipment as a complement rather than a replacement.

The two companies identified data centers and financial institutions requiring precise timing synchronization for 5G and 6G communications infrastructure, and off-road construction and agricultural machinery operating in environments where GNSS availability is limited, as near-term application targets.

Murata described the space domain as a new growth area, framing the partnership as part of a broader commitment to advancing positioning and timing synchronization as foundational technology across communications infrastructure, industrial equipment, mobility and consumer IoT. The company’s scale — it is among the world’s largest manufacturers of passive electronic components — gives the partnership potential reach across global industrial supply chains that few LEO PNT agreements to date have carried.

The announcement follows Xona’s appearance in GPS Innovation Alliance testimony before the House Energy and Commerce Subcommittee on Communications and Technology last week, where GPSIA executive director Lisa Dyer cited six Xona satellite launches planned for this fall and called on Congress to urge FCC approval of the company’s pending radionavigation-satellite service license application.

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“Chasing Lightning: Detecting, Characterizing, and Identifying a Powerful Space-Based GNSS Interference Source” is the title of a new paper Zachary Clements, Argyris Kriezis, and Prof Todd Humphreys. It details how, after almost two years of effort, they were able to identify a constellation of Russian early warning satellites in Molniya (“lightning”) orbits as the source of a series of difficult-to-detect disruptions to GPS signals. 

The paper identified 75 events over a seven-year period in which terrestrial reference stations operated by the International GNSS Service in Europe, Greenland and Canada recorded simultaneous and significant drops in carrier to noise ratio (CNR). 

The story of this jammer hunt in space began in September 2024. During a presentation to the Civil GPS Service Interface Committee  in Baltimore, Humphreys opined “There is every reason to believe China’s BeiDou global navigation satellite system has the ability to imitate American GPS signals and those of Europe’s Galileo,” His remarks were reported in SpaceNews along with speculation about Russia’s capabilities.

The SpaceNews article prompted a call to the Resilient Navigation and Timing Foundation from a researcher in the United Kingdom. The researcher reported that deliberate disruption from space was not just speculation – he had observed it. While the researcher did not want to be publicly identified, he was happy to provide the data and allow others to confirm his findings.

With the researcher’s permission, the Foundation connected him with several GNSS experts who could confirm his findings and met with U.S. government officials to convey the extensive data package.

Clements and Humphreys reported on their initial findings in the paper “Transient Space-Based GNSS Interference: Observations and Analysis” at the Institute of Navigation Conference in September 2025. At that point they had not yet identified the source of the interference.

In the new paper the researchers outline how they accessed data from 165 reference stations. Seventy-five simultaneous drops in CNR across multiple stations, with at least one station recording a drop of 5 dB or more, were identified. 

Humphreys is confident that the interference is purposeful, not hardware malfunctions or accidental emissions. 

“The pattern is far too consistent for this to be accidental. In fact, our data shows it has to be intentional.” 

The interference:

• Has almost always been on a weekday – usually Tuesday through Thursday,
• Events are not regularly spaced out and are transient (less than 10 seconds) rather than periodic or continuous as would be expected from an equipment malfunction,
• Events are quite powerful. CNR drops of up to 10 dB have been observed in some cases, and 
• Impacts are to the most commonly used GPS frequency, L1, but don’t affect other GPS bands like L5.

Also, the signals interfering with GPS are not exactly astride the L1 frequency but are slightly offset. They are centered at 1577.5 MHz, about 2 MHz above the GPS L1 center frequency. This may be an effort to test the capability while avoiding detection.

Perhaps most damning, Humphreys’ team has found that the same Russian constellation has been impacting signals from China’s Bei Dou satellite navigation system in an almost identical way since June 2020.

It is clear that one of this constellation’s primary capabilities is disruption and denial of America’s GPS and China’s Bei Dou navigation systems, should the Kremlin decide to do so. A slight change in frequency and an increase in transmitted power is all that is needed to prevent reception across continental size areas.

The new paper provides six insights for GNSS experts and observers. It:

• Provides measurement models and a detection framework for transient wide area interference,
• Details the spatial, temporal, and spectral properties of multiple wide-area GNSS outage events from the space-based interference source and distinguishes these from a naturally occurring solar radio burst,
• Presents a basic satellite identification strategy to narrow the candidate satellites and estimate the minimum satellite altitude at apogee,
• Presents an advanced satellite associate framework using the generalized likelihood ratio test (GRLT) and applies the framework to a test scenario, 
• Details a framework for instantaneously identifying an interference satellite based on a brief time history of TDOA measurements, and gives an error sensitivity analysis, and 
• Combines IGS CNR data and raw wideband samples from two additional receivers in Europe to confidently identify the source, which is revealed to be a small constellation of Russian satellites in Molniya (“lightning”) orbit.

The paper reveals a significant threat to GPS and other GNSS that has heretofore been unknown to the general public. Findings have already been reported by the New York Times and a video about the discovery has been posted on YouTube by the science education channel Veritasium. 

Many in the community expect that it will increase already high levels of concern about the vulnerability of GPS and other GNSS and how it is used as a tool in great power competition. 

Russia has been particularly open about its use interference from terrestrial sources to punish its neighbors in the Baltic and eastern Europe for growing closer to the West. 

In November 2021 as it prepared to invade Ukraine, Russia shot down one of its defunct satellite with a ground-based missile. The following day state-sponsored media threatened that if NATO got in its way in Ukraine, Russia would shoot down all 32 GPS satellites.

While Russia many not have had the capability to destroy all GPS satellites, it is now clear they had the ability to prevent reception of signals across very wide areas of the globe. 

It is unknown how Russia’s threat influenced the West’s actions in Ukraine. Or how Russia’s ability to turn off reception of GPS and other GNSS with the flip of the switch will impact international relations and actions in the future.

What we do know is that Russia and China have terrestrial PNT systems to complement and backup their systems in space. 

Unlike the United Kingdom and France which are building such systems, and South Korea and Saudi Arabia which have them already in place, the United States has yet to act.

GPS is an amazing and priceless asset. Yet without the protection of a robust and resilient complementary and backup system it remains, as a member of the National Security Council once said, “a single point of failure” for America.

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What emerged was a detailed picture of a system that remains the world’s gold standard for civil and military PNT—operationally reliable, economically indispensable—but one whose modernization has fallen behind the pace of threat, and whose complement architecture is now the subject of a spectrum dispute with consequences well beyond the PNT community.

This account is based on the written statements submitted to the subcommittee by the five witnesses.

The five witnesses were Lisa Dyer, executive director of the GPS Innovation Alliance (GPSIA); Sam Matheny, chief executive of the newly launched Merkhet Solutions; Mariam Sorond, CEO and board chair of NextNav; Harold Feld, senior vice president of Public Knowledge; and J. David Grossman, vice president for policy at the Consumer Technology Association.

The constellation: strong record, narrowing margins

Dyer’s written statement provided the most technically grounded account of GPS’s current status.

The constellation has not experienced a system-wide outage since achieving full operational capability in 1995. The FAA reports GPS system availability at 99.9999 percent. Thirty-two satellites are on orbit, eight above the 24-satellite minimum required for global coverage. The Wide Area Augmentation System extends accuracy and monitors signal integrity across the National Airspace System.

Against that record, Dyer placed a more pressing set of facts. Eight of the 32 satellites are operating on a single string—one subsystem failure each from becoming non-operational. More consequentially, on April 17, 2026, the Space Force terminated the GPS Next Generation Operational Control System program, the long-delayed ground-segment effort that had run more than a decade behind schedule and triggered a Nunn-McCurdy cost breach. Dyer framed the cancellation as an overdue clearing of the path for rapid modernization, and for what she described as a more deliberate integration of commercial satellite PNT data into military operations.

She also documented a capability asymmetry that the subcommittee has not previously examined at this level of specificity. GPS III satellites deliver eight times the anti-jamming protection for military users over their predecessors. GPS IIIF satellites, when fielded, will deliver 63 times. Neither generation extends those protections to civil, commercial or scientific signals. Dyer argued the civil-signal gap carries national security implications precisely because aviation, maritime and surface transportation operators—sectors that depend on civil GPS signals—provide mission-critical logistical support to the Defense Department.

GPSIA submitted formal recommendations on GPS modernization to the defense subcommittees of both Appropriations Committees and both Armed Services Committees the week of the hearing. In September 2025, the Alliance sent a letter to Secretaries Hegseth and Duffy outlining a range of whole-of-government options for addressing jamming and spoofing.

Interference: from conflict zone to domestic runway

Witnesses presented interference as a problem that has moved decisively from theoretical to operational. Sorond cited two 2022 incidents on U.S. soil: a jamming event of unknown origin that shut down a runway at Dallas–Fort Worth International Airport and disrupted roughly 40 miles of airspace for nearly two days, and a separate unauthorized transmitter that interfered with GPS operations at Denver International Airport, affecting both aircraft and air traffic control. Feld’s written statement pointed to a more recent example: Russia’s jamming of the GPS systems aboard the RAF aircraft carrying UK Defense Minister John Healey as he returned from a visit to Estonia. Dyer referenced third-party data aggregating more than 55,000 reported GPS interference events in commercial aviation in 2025—a 24 percent increase over 2024—noting that while the majority occurred overseas and near active conflict zones, a portion occurred within U.S. airspace or on approaches to U.S. destinations.

Dyer was pointed on enforcement. The legal framework is not the problem—federal law already prohibits the manufacture, sale and operation of jamming equipment that interferes with authorized radio communications. In her written statement, she argued that the FCC and the Department of Transportation lack the budget and personnel to enforce those laws, coordinate a whole-of-government response, or adequately address the growing volume of incidents. She called on Congress to provide both agencies with the resources to meet their existing mandates.

The complement landscape: consensus on need, but not on method

Where the panel converged on the modernization and interference questions, it divided sharply on the path to a resilient complementary architecture.

Matheny testified on behalf of Merkhet Solutions, an independent company launched June 2 to commercialize the Broadcast Positioning System (BPS), a terrestrial PNT technology developed at the National Association of Broadcasters starting in 2021. BPS embeds timing and tower-location data within ATSC 3.0 transmission signals. A single tower provides traceable time; multiple towers enable positioning by the same multilateration geometry as GPS. The system requires no internet, satellite or cellular connectivity, operates on existing licensed broadcast spectrum, and supports passive, unlimited simultaneous reception.

Matheny cited a 2025 peer-reviewed NIST finding—produced under a 2024 cooperative research and development agreement—that BPS time-transfer performance is “comparable to or better than GNSS” and constitutes a “viable complementary PNT solution.” A Department of Transportation field trial with Dominion Energy, contracted in August 2025, is underway at a major East Coast substation, assessing BPS performance for grid timing applications. Merkhet currently has deployments in Washington, D.C., Baltimore and Denver. ATSC 3.0 is live in 80 markets reaching more than 75 percent of the U.S. population.

NextNav’s position was presented by Sorond. The company’s Pinnacle vertical-location service is operational in more than 4,400 cities, serves more than 90 percent of U.S. commercial buildings taller than three stories, and provides commercial Z-axis with deployments on all three national wireless carriers and FirstNet. NextNav holds more than 150 patents and describes itself as the largest license holder in the only band the FCC has designated for ground-based positioning.

The company has a petition pending before the FCC that it characterizes as a modernization of its existing licenses in the 902–928 MHz band, to support what it describes as a 5G-based horizontal PNT complement and backup to GPS, deployable on existing wireless infrastructure at no direct cost to taxpayers. The band supports a wide range of licensed and unlicensed operations — among them electronic toll collection systems such as E-ZPass, utility smart meters, home security alarms, agricultural sensors, RFID inventory systems and medical alert devices — that collectively represent decades of investment built on the FCC’s existing coexistence framework.

On the question of modernization, Feld argued that the petition does not update existing rules but asks the FCC to eliminate them—specifically, the protective conditions the Commission attached to the M-LMS licenses when it created them in 1995. That order explicitly acknowledged that Part 15 unlicensed devices had “developed and proliferated in this band and are providing services that are valuable and in the public interest,” and conditioned the new licenses on field testing to demonstrate no unacceptable interference. Feld wrote that NextNav has since “consistently requested that the FCC eliminate the rules protecting unlicensed operations in the band” rather than pursue the cooperative coexistence the 1995 order envisioned.

On the cost question, Feld wrote that the proposed transaction would exchange roughly 14 MHz of shared, low-power spectrum with a partial national footprint for 15 MHz of full-power, flexible-use national spectrum—rights that would be worth billions of dollars if acquired at auction. Feld wrote that, based on the company’s filings, PNT would occupy a small fraction of the resulting network capacity, with the remainder available for mobile carrier use. On the question of deployability, Feld wrote that the proposal would require development of new chips and new 5G standards before any commercial deployment—a process that would take years and depends on wireless carrier adoption that has not been secured.

Grossman characterized the proposal as a structural reconfiguration of the band’s operating environment, not a marginal technical adjustment, and argued that the record of innovation built on existing rules must be weighed against claims of future benefit.

The LEO tier: commercial systems advancing without Washington

Running through the hearing but never its explicit focus was the accumulating progress in commercial low Earth orbit PNT—the tier that may ultimately prove most consequential for complementary architecture.

Dyer described three U.S. companies in various stages of deployment. Iridium operates the first commercial LEO PNT system in the United States, with more than 70 partners across 25 states. TrustPoint is developing a C-band constellation designed for orbital, signal and frequency diversity relative to L-band GPS; three satellites are on orbit, four more in development, with commercial service targeted for 2027. Xona is broadcasting a new signal designed for compatibility with existing GPS receiver infrastructure, scaling manufacturing in California with six launches planned this fall. GPSIA formally recommended that Congress urge FCC approval of Xona’s pending radionavigation-satellite service license application (ICFS File No. SAT-LOA-2023-0711-00165).

Feld anchored the panel’s broader policy argument in the GPS-as-public-good framing, warning against any architecture evolution that would introduce tiered access, impose new costs on agricultural and rural users who rely on free GPS today, or allow the existing system to degrade in favor of proprietary alternatives. He called for privacy-by-design principles to be incorporated into next-generation PNT at the system level rather than addressed through post-hoc regulation.

The record as it stands

The hearing did not resolve the FCC proceedings it illuminated. Its contribution was to put the state of the U.S. PNT posture on the legislative record at a moment when three distinct tracks—GPS modernization, interference enforcement and complement architecture—are simultaneously in motion, each with its own pending proceedings and its own constituency of stakeholders whose written positions now form part of the official record.

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The system is embedded across critical civilian infrastructure as well, with approximately 90 percent of U.S. 911 call centers relying on Safran timing technology. On the defense side, the SecureSync supports applications ranging from GPS-disciplined synchronization in standard infrastructure to M-Code enabled timing for military operations requiring the highest levels of security and integrity — including the Sentinel A4 radar program, where M-Code SecureSync units were integrated to strengthen resilient PNT performance against jamming and spoofing threats. 

“Timing has been foundational to who we are since day one, and this milestone is a testament to the trust our customers have placed in SecureSync for nearly two decades,” said Trevor Dougherty, Vice President of Sales and Marketing at Safran Federal Systems. “In an environment where a fraction of a second can mean the difference between success and failure, we don’t just deliver precise time — we make it resilient.”

The announcement comes alongside continued development of next-generation timing capabilities. In April, Infleqtion announced availability of the first quantum-enabled precision timing solution developed in partnership with Safran Electronics and Defense, integrating Infleqtion’s Tiqker quantum optical clock with Safran’s White Rabbit and SecureSync systems. White Rabbit technology enables picosecond-level time distribution — approximately a thousand times more precise than nanosecond-class timing — positioning the SecureSync platform for the next tier of defense and infrastructure timing requirements as GPS-dependent architectures come under increasing pressure. 

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The release enables integration of Iridium Satellite Time and Location signals directly into VectorNav’s INS architecture alongside inertial and GNSS data. In testing, STL-aided navigation demonstrated positioning performance within approximately 50 meters CEP in GNSS-denied conditions while maintaining continuous inertial position, velocity, and attitude outputs. The Iridium constellation’s 66 active satellites operate at roughly 780 kilometers — compared to approximately 20,000 kilometers for GPS — producing surface signals up to 1,000 times stronger than GPS, improving resistance to jamming, attenuation, and environmental obstruction.

The VN-210E provides four independent serial interfaces and a tightly coupled extended Kalman filter, allowing LEO-derived measurements to be incorporated alongside GNSS, M-Code, vision-based navigation, and other assured PNT inputs. The development kit includes the VN-210E, NAL Technologies’ ALTM Micro-D receiver, a one-year Iridium development license, and reference integration guidance and software tools.

“Inertial remains the foundation,” said Andrew Greer, Senior Director of Business Development at VectorNav. “LEO signals add another layer of resilience. By fusing multiple independent sources, we maintain a stable navigation solution when any single input is degraded or denied.”

Future development will focus on deeper hardware integration, reduced SWaP-C, and streamlined deployment for production programs.

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At the PNT Leadership Summit last September, Locata CEO Nunzio Gambale put a blunt question on the screen again and again: “What’s your replacement?”

He asked it over ports, offshore energy projects, precision agriculture systems and critical infrastructure sites operating in what his presentation called “red zones”—places where GNSS-dependent systems may fail, degrade or become unreliable because of jamming, spoofing or other forms of interference. Across those examples, the warning was the same: high-value civilian systems have been built around precision positioning, navigation and timing, but many still have no credible replacement when the signals they depend on are denied.

That argument has become progressively more difficult to dismiss.

Only months earlier, Gambale said, Ukraine’s June 1, 2025, Operation Spider Web demonstrated how low-cost, precisely coordinated stealth drone attacks could reach strategic targets far beyond the front lines. Ukraine said it used 117 drones, and the Council on Foreign Relations described the attack as evidence that low-cost precision strikes are becoming accessible to many state and non-state actors.

For Gambale, Operation Spider Web has forever changed the strategic logic of PNT. If the now ubiquitous drones can use satellite navigation to reach strategic assets, governments and operators defending those assets will have to increasingly jam, spoof or otherwise deny the signals those drones rely on. The result is a new kind of collateral damage: Civilian systems that depend on the same signals may be disrupted by the defensive measures intended to protect national infrastructure.

That was the September argument.

Since then, the jamming and spoofing environment has become more urgent, particularly around the Persian Gulf and the Strait of Hormuz. Meanwhile, in the Baltic area, Russian electronic warfare is already turning that risk into a live political and operational crisis. In May, Ukrainian officials said Russian electronic warfare had deliberately diverted Ukrainian drones into Latvian airspace, with repeated incursions culminating in explosions at an oil storage facility and contributing to the collapse of Latvia’s government. Inside GNSS+ reported that widespread GNSS interference in the Gulf and Strait of Hormuz region coincided with sharp disruption in commercial shipping, with maritime analytics providers documenting more than 1,100 vessels affected by GPS and AIS interference in a 24-hour period, including ships falsely positioned at airports, a nuclear power plant and on Iranian land.

That escalation makes Gambale’s question feel less like a conference provocation and more like an operational imperative.

The resulting challenge is more difficult than simply asking for a backup to GPS. For Gambale, that phrase is too vague to be useful. The real question is application-specific. 

“This isn’t simply about backing up GPS,” Gambale said. “The point of PNT is the outcome: What the application requires, and what can still deliver it when GPS is degraded, denied or no longer trusted.”

That is the core of his argument. The world did not adopt GNSS merely as a convenience; it built entire classes of infrastructure, automation and digital systems on top of it. Now the same signal dependency that enabled enormous economic value has also become a systemic vulnerability.

The Civilian Problem Has Changed 

For decades, GNSS interference was often framed as a military concern. Jamming and spoofing belonged to battlefields, contested borders and electronic warfare scenarios. Gambale believes that framing is “no longer even close to the reality.”

The drone era has changed the logic. If hostile drones use GNSS to navigate, then defending critical infrastructure absolutely demands the denial of that same signal locally. In other words, the jamming will not come only from the adversary; it will inevitably also come from the government or operator trying to protect its own critical assets.

“What’s the first thing you need to do for anti-drone systems?” Gambale said. “You need to jam the GPS, so that the enemy can’t use the same signal that you’re using. I can tell you categorically that in, say, the UAE, it’s not the U.S. or Israel or Iran that’s jamming Dubai or Abu Dhabi. It’s the UAE itself. We’ve heard credible reports that a GNSS jammer is now installed at the top of the Burj Khalifa. Think about that. It’s called ‘frequency fratricide’… and the Golden Dome, Drone Walls and many other national protection systems you see being built are now undeniable proof that ‘jam yourselves’ is the future.”

That creates what he sees as the new civilian crisis: The same denial zone meant to protect national strategic sites will inevitably disable the civilian systems built around satellite PNT.

“If you want to deny this magical capability to your enemy, you have to deny it to the areas around your critical infrastructure,” Gambale said. “However, you then jam the surveyors, you jam the harbor pilots bringing ships into port, you jam all of the autonomous systems, you jam the mobile phone technologies, you jam the timing for data centers, you jam the landing systems for aircraft. Uber Eats. Waymo. Google Maps.”

That argument is not merely a Locata argument. Gambale cites Doug Taggart, president of Overlook Systems Technologies and an ION Fellow, in the Spring 2026 ION Newsletter. Taggart argued that GPS now underpins transportation safety, economic activity, communication networks, precision agriculture and critical infrastructure, while the United States has spent more than 25 years struggling to identify a backup. Taggart’s conclusion was that resilient PNT capability should be understood as an inherently governmental responsibility, whether the physical systems are government-operated or commercially provided.

That framing shifts the debate from product or solution selection to public responsibility. The issue is not whether GPS remains essential. It does. The issue is whether critical systems can continue operating when GPS is unavailable, untrusted or locally denied.

The Port Test: What Happens When Precision Stops?

Gambale’s most concrete example, from Locata’s own experience in the jamming zones, is port automation. In his summit presentation, he used the Port of Gdańsk and major Baltic infrastructure projects to illustrate the new PNT reality. The point was not simply that ports use GNSS. It was that modern automation systems, such as in ports, logistics hubs, etc., all depend on very precise positioning—continuously and reliably.

The presentation described a $3 billion Port of Gdańsk expansion, with automation as a key part of Polish port infrastructure. It also described fully autonomous rubber-tired gantries—25 ordered, 26 meters high by 30 meters wide, $20 million each, using three RTK GNSS systems for autosteer and placement—with a requirement of less than 2 centimeters, 3 sigma, 24/7/365, without fail.

Large autonomous gantries and other automated systems do not need “some” positioning. They must have centimeter-level positioning, all day, every day. If the position solution degrades, the machine does not simply become less efficient. It stops dead.

“These machines are automated, and they’re stacking containers on top of one another autonomously, without any human in the loop,” Gambale said. “They must have two- to five-centimeter positioning, or else the entire system doesn’t work. This is not some academic argument. When an infrastructure site like Gdansk is jammed, the company literally owns $500 million dollars’ worth of ‘bricks.’ The company’s need for centimeter-level GNSS is dire. Jamming can cost millions per day. And that is a clear and existential threat to a business’ existence.”

He framed the problem in operational terms. A lower-accuracy backup may sound useful on a policy slide, but if it cannot support the application’s required precision, it does not solve the problem.

“If a ‘solution’ blows out past five centimeters, the machines must stop,” he said. “Something that gives you 2 meters of ‘GPS backup’ is of absolutely no use to that type of application.”

That distinction is central to his argument. The market does not need a generic conversation about backup. It needs a performance conversation: what accuracy, what timing, what integrity, what availability, what resilience under interference, and what happens when the system is spoofed?

If the answer does not meet the application requirements, then the infrastructure remains exposed, critically compromised and vulnerable.

Precision as Infrastructure

Gambale extends the same argument to offshore construction, surveying, logistics and warehousing sites, and precision agriculture. In each case, PNT is not a convenience layered onto the application. It is part of the operating system.

Gambale pointed out that view is strongly supported by ESA’s March 2024 NAVAC PNT Vision 2035 White Paper, produced under the guidance of NAVAC Chaiman, Luis Mayo. According to the report, more than 6.5 billion GNSS devices were already installed worldwide by 2021, with the installed base expected to grow to 10.6 billion by 2031. Also, according to the report, roughly 10% of EU GDP relies on GNSS to some degree, while consumer, IoT and automotive applications represent more than 90% of the market.

But the report’s most important point for Gambale’s thesis is not market size. It is dependency. NAVAC warns that as GNSS use spread across application domains, society built an increasingly deep dependence on these systems. The report identifies jamming, spoofing and interference as growing concerns, and specifically notes that accurate timing is the main critical use case for critical infrastructure.

That supports Gambale’s point: PNT is no longer a navigation feature. It is a dependency layer underneath automation, logistics, energy, telecom, finance, data centers, transportation and every nation’s digital economy and critical infrastructure.

The performance requirements for modern and emerging applications are also not abstract. Gambale points out that NAVAC’s 2035 requirements table points to centimeter-class horizontal and vertical accuracy requirements for many high-value applications: 2 to 15 cm for precision irrigation and cultivation, 4 to 6 cm for kinematic survey, and 10 cm for Level 3-and-above road autonomy and collision avoidance. For timing-dependent applications such as the coming 6G and DVB networks, the requirement moves from position into time, with NAVAC citing the need for 10-ns timing accuracy.

A backup that preserves rough continuity may be valuable for some applications. But it is not enough for a port that needs centimeters, a precision agriculture workflow that depends on corrected guidance, or a timing network that needs nanosecond-level synchronization.

In his PNT Leadership Summit presentation, Gambale cites Baltic offshore wind construction and a $5.1 billion Baltic Power project that is essential for Poland’s energy security and independence, including 76 Vestas 15 MW turbines. He also frames offshore construction requirements in hard operational terms: precision construction needs less than 5 centimeters at 3 sigma, 24/7/365, without fail; and ship dynamic position systems (which automatically maintains a vessel’s exact position and heading using its own propellers and thrusters) needs less than 10 centimeters at 3 sigma to work.

In agriculture, Gambale points out, interference does not need to jam an entire operating area to cause disruption. If today’s essential correction infrastructure is vulnerable, the precision layer then collapses.

“In the Ukraine, it’s now become even more trivial to jam a huge area of farmland,” he said. “You don’t have to try to jam the whole area. You just jam the local reference station, and that whole area is toast.”

That observation turns PNT into a food security issue, not simply a navigation issue. A tractor autosteer system, a surveyor, a road construction company, a port crane, an offshore construction vessel and a data center may appear to occupy different markets, but they all share the same dependency: high-confidence position and time.

Gambale’s message is that resilience must be judged against the actual application, not against a generic idea of signal continuity.

Do Not Deploy Your Grandfather’s GPS Backup

One of the strongest lines in Gambale’s presentation was: “Do not deploy your grandfather’s GPS backup.”

It is an intentionally provocative phrase, but the point is technical. Many valuable present-day applications—and most future applications—need high accuracy, high confidence and trusted timing. Systems that provide only low-accuracy continuity do have value for some uses, but they will not keep a modern autonomous port or logistics site, precision agriculture workflow, road construction site or high-value industrial operation running.

ESA’s NAVAC report reaches a similar conclusion from a different angle. It says future PNT will be delivered through a combination of alternative, independent and complementary sources: multiple GNSS in different orbits and frequencies, cellular networks, terrestrial systems such as eLoran, Wi-Fi and signals of opportunity, augmentation systems, inertial sensors, quantum sensors, magnetic sensors, miniature atomic clocks and digital maps. It also concludes that future systems will increasingly operate as “systems of systems” designed to meet the performance required for a given application.

That is very close to Gambale’s “what does your application need?” mantra. A technology is not useful because it belongs to a fashionable category. It is useful if it meets the required accuracy, timing, integrity and resilience for the mission.

And those requirements are getting more difficult, not easier.

NAVAC states that “accuracy is addictive,” that users will demand more robust solutions less susceptible to natural or man-made disruption, and that assured PNT demand will grow tenfold by 2035, including in physically challenging environments such as indoors, multi-story buildings, urban canyons and underground facilities.

That is why Gambale’s critique of low-performance complementary PNT is so sharp. “There is no point deploying technology that gets you three quarters of the way there, and the port is still stopped,” he said.

Positioning Depends on Timing

For Gambale, timing is the most underappreciated part of the PNT discussion. “PNT only exists because of the T,” he said.

That statement is more than a slogan. Positioning systems depend on timing. Digital infrastructure depends on timing. Telecom, financial systems, data centers, power grids, autonomous systems and distributed industrial operations all require trusted time at levels appropriate to their applications.

Taggart makes the same point in institutional terms. His ION Newsletter column notes that, through NIST, the Department of Commerce maintains the nation’s time and frequency standards, while NIST and the U.S. Naval Observatory provide official U.S. precise-time contributions to the Bureau International des Poids et Mesures, which calculates Coordinated Universal Time. He also notes that financial markets, telecommunications services, data networks, electric power grids, pipelines and SCADA services all depend on timing derived from GPS.

For Gambale, that dependency should drive a different standard of performance. He argues the industry too often talks about timing in terms of minimum standards rather than future capability.

“The world isn’t asking for worse timing,” he said. “As you get better and better timing, you get better and better positioning, and better and better digital capabilities. That’s why our Locata team has dedicated several decades of innovation to be able to deliver GNSS-free, sub-nanosecond synchronization and time transfer.”

He explains the issue in terms engineers understand: error budgets. Every system has a set of error sources—timing error, multipath, atmospheric effects, electronic variation, geometry, signal processing limits and more. If timing consumes too much of the error budget, there is less margin left for everything else.

“If the bucket is 75% full of timing error, that leaves them a lot less margin to play with,” Gambale said. “However, if we can reduce that timing error budget down to 10% of the bucket, then they’ve got a lot more leeway with the rest of the error budget.”

That is why he sees timing as a foundation, not a feature. Better timing does not merely improve clocks. It improves the ability to position, synchronize, automate and trust distributed systems.

NAVAC also emphasizes timing. The report states that accurate timing is the critical use case for communications and power distribution networks, and it identifies distributed and networked time-scale infrastructures as an important path toward resilient timing applications independent from GNSS.

Multipath, Trust and the Devil in the Real World

Gambale is equally forceful about multipath, explaining why Locata has spent years creating new technology to mitigate this obstacle. In terrestrial and obstructed environments, reflected signals can become one of the dominant sources of error. It is not enough to say a transmitter is nearby or a signal is stronger. The system must manage reflections, geometry and line-of-sight integrity.

“Multipath is the devil,” he said. “It is everywhere, and unless you deal with it, you will never be able to give an accurate position that’s reliable.”

This is where the conversation then turns from availability to trust.

Jamming denies. Spoofing deceives. Multipath corrupts. Each poses a different challenge. A receiver that produces an answer is not necessarily producing a trustworthy answer. In heavily automated systems, that distinction can become dangerous.

Gambale argues that users have become conditioned to trust the box. The receiver gives a position, and the system accepts it. That worked in an era when GNSS was generally available and interference was occasional. It becomes much more fragile in an environment of persistent jamming and spoofing.

“It’s all about trust,” Gambale said. “Even if GPS comes back, many huge companies no longer want to depend on it, because it is no longer trustworthy.”

That may be the most important transition in the PNT debate. Availability asks whether the signal exists. Trust asks whether the system should act on it.

From AIR to Sovereignty

In the summit presentation, Gambale framed the future of complementary PNT around three validated attributes: Accuracy, Integrity and Resilience—AIR.

Accuracy means the system can meet the application’s actual performance requirement. Integrity means the user can trust the answer, especially in safety-of-life or mission-critical applications. Resilience means the system continues to function—or recovers predictably—under real-world stress. Gambale stated: “Without AIR your application will die!”

Gambale has since added a fourth concept: sovereignty.

For him, sovereignty does not only mean national ownership in a political sense. It means control. Control over the PNT layer that critical systems depend on. Control over the ability to deploy, operate and trust the infrastructure required for the mission. Control over the destiny of an organization, business or site.

Gambale returns repeatedly to the idea that nations and critical infrastructure operators must stop thinking of PNT as an invisible utility that simply arrives from somewhere else. They must treat it as critical infrastructure. Lifeblood for their business.

“Electricity is wonderful,” he said. “It is distributed everywhere. But show me one critical infrastructure site that doesn’t have backup batteries or a generator.”

The analogy is simple and powerful. Critical sites rely on the grid, but they do not trust the grid alone. They build backup capability because the consequences of failure are too severe. Gambale believes PNT now requires the same mindset.

The Spectrum Sandbox

His policy prescription is equally direct: create a terrestrial PNT spectrum framework.

“The best thing that America can do to push real PNT resilience forward is to allocate a terrestrial spectrum for the job,” he said. “Give it a slice of spectrum that everybody can play in, if they wish.”

For Gambale, this would create a sandbox for innovation. Satellite systems have protected spectrum. Terrestrial PNT, if it is to become a serious resilience layer, needs a comparable policy foundation. Within that framework, industry, universities and government could build and test systems designed for specific application requirements.

“Allocate spectrum just like the satellites have got spectrum,” he said. “Allocate a terrestrial capability where you can determine what’s required for each application in an area. But give us the sandbox. Then let 1,000 innovations bloom, as was the case in the early days of GPS.”

That argument moves the discussion beyond individual products. It treats PNT resilience as an ecosystem problem. If the United States—or any sovereign nation—wants local, high-confidence PNT capability, then the nation must create the conditions for such systems to exist.

It also fits the broader direction of PNT architecture. NAVAC’s 2035 vision does not imagine one replacement for GNSS. It imagines combinations of systems: space-based, terrestrial, cellular, augmentation-based and sensor-based. It also warns that alternative systems must avoid hidden dependencies on GNSS itself, such as using GNSS as the time reference for supposedly independent ground networks, or as an essential reinitialization of an IMU system.

That warning is central to the Gambale thesis. A backup that depends on the system it is backing up is not a true replacement. A resilience layer that fails under the same conditions as GNSS may add complexity without adding survivability.

Gambale sees the spectrum sandbox as a chance not merely to protect infrastructure, but to create the next exportable PNT architecture.

“If America does it first, and you have all of your bright minds, and the universities, Silicon Valley, and everyone throws some real effort at it, you can do exactly what you do with GPS,” he said. “You can export it all over the world again.”

Then came the line he delivered with a laugh, but not entirely as a joke:

“Make PNT great again.”

The phrase works because the argument underneath it is serious. GPS was one of the United States’ greatest contributions to the modern world. It enabled entire industries. It created enormous civilian and commercial value. But the dependence it enabled has also become a 21st-century infrastructure vulnerability.

As Gambale put it: “The U.S. nation in the 1990s gave the world one of the greatest gifts of all time. That gift has now created one of the biggest problems for the 21st century. That problem must be solved. And Locata has created exceptional new high-accuracy technology that does not depend on GNSS at all. It delivers a level of control and sovereignty that will certainly be part of the ‘future of PNT.’”

For ports, farms, offshore energy projects, logistics hubs, construction sites, autonomous systems and critical infrastructure operators, the need for a solution—for AIR, for control and for sovereignty—is no longer theoretical. The jamming and spoofing environment is real and escalating. The performance requirements are not abstract. And the dependency on a signal that was never designed to carry this much weight is not going away on its own.

That is the state of play. 

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