Competition in satellite positioning has begun to spread from medium Earth orbit at roughly 20,200 km altitude down to low Earth orbit around 500 km. U.S.-based Xona Space Systems launched its demonstration satellite Pulsar-0 on June 23, 2025, and on July 9, 2026, kicked off "Pulsar Verified," a program to validate compatible receivers. The company plans to deploy 258 satellites over the coming years, with initial satellites entering orbit starting in the second half of 2026. This is not yet a global positioning network, but the groundwork is now in place for the transition from a single-satellite radio experiment to mass satellite production and receiver integration.
A 258-Satellite Plan, and a Service That Starts with Just 6
In March 2026, Xona announced a $170 million Series C funding round earmarked for Pulsar deployment and a new factory in Burlingame, California. Belgium's Aerospacelab also received an order for an additional 8 satellites as a transitional manufacturing partner, bridging the gap while Xona ramps up its own domestic U.S. production. Under both companies' official plans, launches begin in the second half of 2026.
According to a schedule Xona executives shared with Ars Technica, the first 6 mass-production satellites will launch in October 2026, with initial service beginning in 2027. Six satellites alone won't provide continuous positioning for users worldwide. Xona explains that it will initially offer intermittent timing signals at mid-latitudes, aiming for at least one satellite to be regularly visible once around 16 satellites are in orbit. Centimeter-level positioning becomes feasible only once four satellites can be seen simultaneously within a region.
The fact that initial customers include precision-timing providers Hoptroff, Fibrolan, and Timebeat reflects this deployment sequence. For fixed installations with known positions, applications that deliver timing to networks or data centers can start with a signal from just a single satellite. But for vehicles or surveying equipment to simultaneously solve for three-dimensional position and receiver clock error using Pulsar alone, more satellites must be visible at once. Commercialization thus begins with time synchronization and expands into positioning as satellite numbers grow.
How 510 km Altitude Changes Signal Power and Sky Dynamics
The orbital altitude the U.S. Federal Communications Commission (FCC) approved for Pulsar-0 is 510±15 km. GPS satellites fly at roughly 20,200 km, with a baseline constellation of 24 satellites across 6 orbital planes designed so that 4 or more satellites are visible from nearly anywhere on Earth. In low Earth orbit, a single satellite covers less ground area and offers shorter visibility windows, which is why Xona plans 258 satellites—more than 10 times the size of GPS's baseline constellation.
The advantage of closer satellites shows up in received signal power and sky motion. According to Xona's specifications, Pulsar's X1/X5 signals reach a maximum received power of -136 dBW, up to 100 times stronger than GPS L1 C/A. This makes signals easier for receivers to track even after attenuation by buildings or trees, and widens the margin before jamming signals can overpower them. Moreover, low-orbit satellites cross the sky in a short time. Because Doppler shift and ranging geometry change rapidly, it becomes easier to separate reflected signals from direct-path signals and to converge on a positioning solution more quickly.
This concept has precedent. Transit, devised by Johns Hopkins University's Applied Physics Laboratory in 1958 and entering full operation in 1964, was the first satellite navigation system, determining submarine positions from the Doppler shift of low-orbit satellites. GPS moved to medium Earth orbit, ranging a small number of satellites simultaneously to continuously output position and time. Today's LEO-PNT systems aim to recapture Transit's orbital and Doppler approach while adding software-defined signals, inter-satellite ranging, and interoperability with existing GNSS.
However, operating hundreds of fast-moving satellites requires aligning each satellite's orbit and clock in real time with high precision. Xona's design aims to move this computation into space itself, using onboard estimation and inter-satellite ranging. While low orbit is a shortcut to stronger signals, it also makes manufacturing, replenishing, and synchronizing the entire constellation more difficult.
1.5 cm Is Not Positioning Accuracy—It's a Single-Satellite Ranging Result
As evidence from Pulsar-0's first year in orbit, Xona cites over 350 transmission passes across four continents, 22 TB of observational data, and tracking by more than 12 receiver manufacturers. The company also rolled out four major on-orbit software updates. According to Xona, these updates reduced single-satellite ranging error from 4.2 cm to 1.5 cm.
It's important not to mistake this 1.5 cm figure for user positioning accuracy. Early single-satellite positioning tests presented by Xona researchers at the Institute of Navigation reported meter-level position accuracy both outdoors and indoors. The figures of 2 cm horizontal accuracy, 4 cm vertical accuracy, and sub-10 ns timing accuracy represent expected specifications for open-sky conditions once the full constellation is in place. The ranging quality confirmed today with a single satellite and future multi-satellite positioning performance need to be evaluated separately.
The same caution applies to jam resistance. Xona has reported, based on field tests in multiple countries, that its signals—up to 100 times stronger plus error correction—reduced by as much as 95% the area over which a jammer could deny GPS. This does not mean jamming is neutralized. Under conditions such as a nearby jamming source, high transmission power, or an unfavorable receiving antenna, Pulsar can still be affected. The value lies in shortening the range over which existing jammers can block signals and in increasing the number of paths that are less likely to be lost simultaneously with GPS.
Getting Receivers Moving Ahead of the Satellites
Pulsar Verified, which launched on July 9, 2026, has been joined by Trimble and Septentrio. On the semiconductor and equipment side, STMicroelectronics and Safran are listed among the initial participants, while StarNav and Keysight represent the testing and receiver side. Xona has adopted X1/X5 signals adjacent to GPS's L1/L5, and says many existing receivers can support them via firmware or software updates. Indeed, Pulsar-0's signals have already been tracked by receivers from more than 12 manufacturers.
Still, a certification program is necessary because compatibility isn't uniform. Even if an antenna and radio front end can pass the frequency, the receiver must also track large Doppler shifts and decode a proprietary navigation message. A compatibility study involving Xona reported that no harmful interference to GPS or Galileo was observed in the commercial receivers tested—but this result doesn't guarantee compatibility across all equipment or operating conditions. Pulsar Verified is the process of translating satellite-side specifications into actual products.
Signal authentication also presumes receiver updates. In Xona's research, a watermark was created by cryptographically inverting 21 of the 1,023 chips that make up the X1 signal, and pseudorange authentication was demonstrated using 150 seconds of data recorded from an on-orbit transmission on July 7, 2025. The design strength is at least 32 bits, and once the full constellation is operational, the goal is 4-second authentication using dual-frequency receivers. However, cryptography cannot prevent signal-delay attacks. Only by layering strong signal power, signal authentication, and concurrent use of GPS can an attacker's options be meaningfully narrowed.
Competing on Layering, Not Replacing GPS
Besides Xona, the European Space Agency (ESA) is also testing low-Earth-orbit positioning. ESA launched the first two Celeste satellites on March 28, 2026, and received Europe's first LEO navigation signal on April 8. The agency is building an 11-satellite demonstration constellation operating at 500–600 km altitude, with plans to add 8 larger satellites plus one small satellite carrying an atomic clock starting in 2027. Using L and S bands in addition to C and UHF frequencies, the project aims to test inter-satellite clock synchronization and multi-layer operation alongside Galileo.
What's driving demand is not positioning accuracy per se, but uninterrupted timing and position. In March 2026, EASA and EUROCONTROL compiled an aviation action plan premised on the assumption that GNSS interference near conflict zones has become routine and its effects extend far beyond those areas. Yet the U.S. Department of Transportation, after demonstrating GPS backup technologies, concluded that no single method can universally replace positioning and navigation. Combining ground-based radio or fiber-optic timing with inertial sensors, while also using multiple satellite signals, better distributes the sources of failure.
Whether Pulsar succeeds will hinge on whether a paid, strong LEO signal can be realistically layered atop the free, globally available GPS. After launches begin in the second half of 2026, three things will matter: how quickly regions achieve simultaneous 4-satellite visibility, whether independent field tests reproduce the claimed accuracy and jam resistance, and whether Pulsar Verified-compatible devices make it into mass-market products. If all three come together, low-Earth-orbit positioning will move beyond simply repeating history and become a new layer of positioning infrastructure.