Precise orbit determination is becoming increasingly critical for satellite navigation, positioning and timing as Low Earth Orbit constellations expand worldwide. Researchers have introduced a new method that combines inter-satellite link data with onboard BeiDou-3 observations to simultaneously resolve LEO and BeiDou-3 Medium Earth Orbit satellite orbits with unprecedented accuracy.
The a by Riko Seibo
Tokyo, Japan (SPX) Aug 20, 2025
Precise orbit determination is becoming increasingly critical for satellite navigation, positioning and timing as Low Earth Orbit constellations expand worldwide. Researchers have introduced a new method that combines inter-satellite link data with onboard BeiDou-3 observations to simultaneously resolve LEO and BeiDou-3 Medium Earth Orbit satellite orbits with unprecedented accuracy.
The approach solves the long-standing challenge of constellation-wide rotation drift by referencing the coordinate system embedded in BeiDou-3 broadcast ephemerides and applying a corrective rotation. Simulation tests reduced LEO orbit errors from more than 20 cm to around 1 cm, enabling high-accuracy, low-latency solutions without dependence on dense global ground station networks.
Large constellations such as Starlink, OneWeb and CENTISPACE face high costs and geopolitical hurdles in maintaining ground tracking infrastructure. Inter-satellite links alleviate this burden but introduce rotational unobservability, where entire constellations shift orientation without an absolute spatial anchor. Existing remedies require post-processed GNSS products or additional infrastructure, raising cost and latency.
The Wuhan University team developed and validated a rotation-corrected integrated POD method fusing inter-satellite and onboard BeiDou-3 GNSS data. Published August 4 in Satellite Navigation, the study demonstrated centimeter-level precision while substantially reducing reliance on ground stations.
In simulations, a 66-satellite LEO constellation equipped with inter-satellite links and onboard BeiDou-3 receivers was analyzed with 24 real BeiDou-3 MEO satellites. Two processing strategies-using either all LEO receivers or only a subset-showed the correction propagated across the entire network. Before correction, cross-track errors reached 40 cm for LEOs and more than 1 m for MEOs. Applying a Helmert transformation based on BeiDou ephemerides reduced errors to just centimeters, even with only partial GNSS receiver coverage.
"This method tackles one of the most stubborn issues in autonomous constellation orbit determination-systematic rotation caused by the lack of absolute spatial reference," said Dr. Kecai Jiang, corresponding author. "By harnessing readily available BDS-3 broadcast ephemerides and inter-satellite measurements, we can deliver centimeter-level precision without waiting for post-processed GNSS products or building extensive ground networks."
The technique could provide global benefits for navigation augmentation, autonomous LEO-based navigation, broadband internet delivery, disaster response and precision agriculture. Its scalability and reduced hardware requirements make it especially attractive for future mega-constellations seeking cost-effective, real-time, high-accuracy orbit determination.
Research Report:Integrated precise orbit determination for LEO constellation and BDS-3 MEO satellites using inter-satellite links and onboard BDS-3 observations
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