Move over, GPS: Navigation satellites in low-Earth orbit are making a comeback

Xona expects its satellites to eventually deliver a timing reference accurate to within 10 nanoseconds. But unlike GPS satellites that carry expensive atomic clocks for accurate timekeeping, Pulsar satellites would rely on a much cheaper software-based solution for precision timing. The Pulsar timing services would become more persistent and available in urban environments once the constellation grows to about 16 satellites in orbit, enabling at least one satellite to be in view on a regular basis, according to Xona. The company also described centimeter-level positioning capability as becoming possible with four Pulsar satellites in view over a region, which it expects to accomplish for “priority regions” before the full constellation is completed. The first customers for Xona and other companies planning satellite navigation systems in low-Earth orbit (LEO) will likely be “organizations that place an exceptionally high value on availability, resilience, integrity, authentication, and precision, and are already accustomed to paying for premium PNT services,” Zak Kassas, director of the Autonomous Systems Perception, Intelligence, and Navigation (ASPIN) Laboratory at The Ohio State University, told Ars. He suggested that such customers would be “defense and national security users and government agencies responsible for resilience.” To replicate the performance of GPS, a satellite navigation system in low-Earth orbit would need about 10 times more satellites than a similar satellite constellation in medium-Earth orbit, Kassas explained. But as the recent rise of Xona and other competitors shows, lower manufacturing and launch costs have made it possible to build and launch such a satellite constellation dedicated to delivering PNT services from low-Earth orbit. The company has already produced the two in-house satellite buses that are scheduled to join the launch in October 2026. When Ars spoke with Xona’s team in June, the satellite buses were undergoing vibration testing to see how well they could endure the simulated stress of rocket launches. Pushing the limits of hardware early and often can provide insight into failures that are much easier to understand and mitigate well before the satellite launches into orbit, Graham said. “I cut my jib with the SpaceX mentality of tests… a test that doesn’t break something or show you something new is not super valuable,” Graham explained. “Let’s just try it and see what works, see what breaks, and then make it stronger.” However, Xona took a different route by instead making Pulsar satellite signals compatible with ground receivers designed for L1 or L5 band signals. That decision helps to make Pulsar satellite signals work more readily with ground receivers and chipsets that are currently designed for L-band signals from GPS and other global navigation satellite systems. The company claims some existing hardware and receivers would only require a firmware and software update. “Our engineers review the manufacturer’s product and its intended application, develop a tailored test plan together, and validate that the implementation receives the signal,” Perkins told Ars. “The beauty is that it doesn’t actually require the hardware to be redesigned.” Toward that end, Xona announced its Pulsar Verified program on July 9, 2026, that provides the custom test plan for each hardware manufacturer to ensure compatibility with Pulsar signals. Companies that have already signed up for the program include leading PNT companies such as Trimble and Septentrio, along with STMicroelectronics, Safran, StarNav, and Keysight. “What makes Xona stand out from other contenders is that they’re aiming to create receiver ecosystem adoption,” said Kassas at Ohio State. The rise of more satellite constellations in low-Earth orbit has even created new opportunities for independent navigation solutions. Kassas and his colleagues have used off-the-shelf antennas and created software algorithms to harness the signals from satellites operated by Xona and many other satellite providers that do not even operate dedicated PNT services, including Starlink. Their navigation solution’s eavesdropping technique measures the signals’ Doppler shifts—a throwback to the Transit satellite system’s pioneering demonstration of satellite-based navigation capabilities.