Linking GPS-Style Satellites to Moon Orbiters Could Cut Navigation Drift 20-Fold, Chinese Simulation Finds

Satellite navigation systems such as GPS guide ships and help drivers avoid closed roads, but they have a weakness. They depend on ground stations that could go offline because of blackouts, natural disasters or cyberattacks. If those stations stay offline long enough, the whole constellation begins to drift. A research team in Shanghai says it has a possible fix: tie the satellites to others orbiting the moon.

The paper, led by Xia Lin and Baojun Lin at the Shanghai Engineering Center for Microsatellites, appears in the journal Satellite Navigation. It addresses a problem aerospace engineers have tried to solve for years with little success. Today's constellations use a technique called time-division multiple access to talk to neighboring satellites, measuring the distances between them down to the centimeter. That tells them how far apart they are, but not where they are in absolute terms.

The reason is that Earth's gravity is nearly symmetrical around its rotation axis. All the satellites in an orbital shell can therefore drift together relative to the ground, a problem orbital dynamicists call an orientational rank deficiency. Position errors slowly build up unless ground stations correct them. If the stations are down for days or weeks, those errors could grow to significant distances. Other proposed fixes, including star trackers, pulsar counters and forecasting orbits ahead of time, have not delivered the precision the global system needs.

The team's idea is to use satellites in cislunar space, orbiting the moon rather than Earth. Because those satellites are not affected by the same drift, they give the Earth constellation an outside reference to notice and correct it. For the lunar satellites, the researchers chose elliptical lunar frozen orbits, the paths NASA's LunaNet and ESA's Moonlight projects plan to use to support missions at the moon's south pole.

They tested the idea in a 60-day simulation using real data from 24 operational BeiDou-3 satellites in medium Earth orbit and a simulated cross-link with four lunar orbiters. With Earth-only cross-links and no ground correction, the constellation drifted about 7.85 meters (25.8 feet) over two months. With trajectory prediction, drift fell to 0.6 meters (about 2 feet) by day 60. The joint Earth-moon network did best, at just 0.35 meters (1.1 feet), roughly a 20-fold improvement over the uncorrected case.

The benefit runs both ways. Earth-orbiting satellites can send corrections to the lunar ones. The correction was less precise in that direction, but the four simulated lunar orbiters still stayed within 2.26 meters (7.4 feet) of their expected positions.

The results come from simulation, and the authors call the analysis preliminary. Still, it suggests infrastructure planned for crewed lunar operations could also protect navigation on Earth. Precise positioning will be critical for future astronauts working on the lunar surface, and the same network could keep the satellites overhead accurate when the ground goes quiet. The study is published in Satellite Navigation (DOI: 10.1186/s43020-026-00217-9).