Real-time Kinematic Precise Orbit Determination for LEO Satellites via an Uncombined Formulation: Opportunities and Challenges

Kurzfassung

Over the past decades, more than ten thousand satellites have been deployed in low Earth orbit (LEO), between 300 and 2000 km, mainly for global broadband communications and Earth Observation applications. Furthermore, dedicated Positioning, Navigation, and Timing (PNT) constellations are also foreseen in LEO to augment the current Global Navigation Satellite Systems (GNSS). A key aspect of (mega-)constellation management and on-board operations is therefore the ability to compute the Precise Orbit Determination (POD) user solution, i.e., potentially on board and in real time. Space-borne receiver capability of tracking multi-GNSS/-frequency data represents a unique opportunity to exploit legacy GNSS signals, achieving autonomous orbit determination & time synchronization. This contribution investigates Kinematic POD, thus neglecting any a priori orbital dynamics model, while using an undifferenced and uncombined Precise Point Positioning (PPP) formulation. The latter is scalable to an arbitrary number of signals/frequencies, while estimating slant dispersive delays that could be of interest for atmosphere remote sensing. The onboard availability of PPP corrections is possible via Galileo High Accuracy Service (HAS), which enables dm-level accuracy in real time. A rigorous data quality control, based on a Detection-Adaptation-Identification (DIA) procedure for geometry-free and geometry-based models, is adopted to mitigate the high sensitivity of kinematic solutions when subject to mismodelling errors. Ultimately, the kinematic POD performance, applied on Sentinel-6A data from 2026, are presented in this work, along with a discussion of the principal opportunities and challenges for Kinematic POD.