GPS leaves us stranded inside buildings. An alternative is already in orbit and has shown that it can arrive indoors

We enter a shopping center, go down to a parking lot or cross the door of a station and the blue dot begins to hesitate. Sometimes it takes a while to react, other times puts us on the next street and, in the worst cases, stop following us completely. We have become accustomed to the mobile phone almost always knowing where we are, but it is enough to put several walls and ceilings in the way to remember that the signals that arrive from space still have very specific limits.

The answer you propose Xona Space Systems It’s called Pulsar and it already has hardware working in space. Its first dedicated satellite, Press-0has transmitted signals that could be followed from inside a building, a relevant test because it directly addresses one of the weak points of traditional satellite navigation. The demonstration, however, is only the first step, while offering a stable, immediate and accurate position indoors requires more satellites, compatible receivers and coverage that has yet to be deployed.

Satellites closest to the Earth’s surface

Although we usually call everything GPS, that name corresponds only to the Global Positioning System of the United States. Our mobiles can also combine signals from Galileo, from the European Union; GLONASS, from Russia; and BeiDou, from Chinaall of them included under the term GNSS. Their architectures are not identical, but they share a difficulty: transmissions arrive very weak after traveling thousands of kilometers. In the case of the American system, the GPS office itself recognizes that buildings can block the signal and that its bounces off walls introduce errors in the position.

Recreation of Xona satellites

Pulsar attempts to change that relationship by bringing the transmitters much closer to the surface. While the GPS satellites orbit at about 20,200 kilometers altitude, the architecture requested by Xona would place them around 1,080 kilometersa distance that allows the signal to arrive with greater power. Its rapid movement also generates Doppler variations that can provide additional information to the position calculation. The advantage comes at a price: each ship covers less territory and remains visible for less time, so hundreds are needed to offer continuous service throughout the planet.

The project was not born with Pulsar-0 either. Xona carried out a first orbital demonstration with Huginn in 2022an experimental payload that allowed its architecture to be tested before launching, in 2025, a dedicated satellite. Since then, the company has transmitted for hundreds of passes, updated its in-orbit software, and managed to get different commercial receivers to track their emissions. It has also opened its own factory in California and ordered new units from Aerospacelab. There is, therefore, hardware and an industrial base in place, although the constellation necessary to provide continuous service has yet to be built.

A view of Xona’s laboratory

What Xona has demonstrated inside a building is not yet comparable navigation to what we expect from a mobile phone, although there is an important nuance: the entire test was carried out with a single satellite and receivers installed in specific positions. In a work signed by engineers from the company itself, an indoor antenna accumulated measurements of Pulsar-0 during its passage to estimate the position, while the comparison equipment failed to acquire GPS signals in the main test. This ended with 38.7 meters of horizontal error; Other selected records were between 0.6 and 3 meters, although in those cases the algorithm started from an initial estimate close to the real location. For a single experimental ship, the result is promising; To guide us as we walk indoors, the net still needs to be deployed.

The next announced step is to launch a first batch of six production satellites, scheduled for October 2026, and initially offer intermittent coverage to some time-sync customers. For Pulsar to provide immediate and precise positions, several ships will be required to be visible at the same time, much broader coverage and receptors capable of interpreting their signals. It will not replace GPS overnight nor will it solve any interior problem on its own. But what we have seen demonstrates at least one thing concrete: a navigation signal sent from low orbit can be received inside a building at a point where GPS failed to do so.

Images | Xona (1, 2)

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