Operational Scheduling and Analysis of Ground Segment for Regional LEO-PNT Architecture

Kihyun Kim, Donguk Kim, and O-Jong Kim

Abstract:	Global Navigation Satellite Systems (GNSS) operating in Medium Earth Orbit (MEO) are the foundation of many critical infrastructures, yet their weak signal strength makes them highly vulnerable to radio frequency interference. As a complementary or backup solution, Low Earth Orbit (LEO) satellites, which provide stronger signals, have gained significant attention, and research on LEO for Positioning, Navigation, and Timing (PNT) is actively progressing. This study focuses on the Dedicated approach with an emphasis on regional LEO-PNT operations, aiming to identify operational strategies and design elements that ensure stable Signal-in-Space User Range Error (SIS URE). Several key factors are considered. First, satellite orbit design determines how many satellites can be simultaneously observed and controlled within the region of interest. Because of their lower altitude, LEO systems require sufficient constellation size to secure continuous service. Second, the choice of onboard clock directly affects system synchronization and ranging accuracy. While high-precision atomic clocks enhance performance, they increase cost and power consumption, making careful selection essential according to mission requirements and operational constraints. Third, Inter-Satellite Links (ISL) represent another critical factor. Without ISL, each satellite must independently communicate with ground facilities for orbit determination and time synchronization, resulting in high ground dependency and limited-service continuity. With ISL, however, a satellite in contact with a ground station can distribute acquired data to other satellites, reducing reliance on ground infrastructure while demanding advanced communication hardware and precise link maintenance. Lastly, GNSS receivers on LEO satellites can support orbit determination and synchronization, easing the burden on ground facilities. However, using GNSS signals may impose limitations on establishing a fully independent PNT system, and their utilization may be restricted in GNSS-denied environments. By comprehensively analyzing these factors, this study presents analysis results on regional LEO-PNT architectures that minimize ground reliance while ensuring stable and reliable service.
Published in:	Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025) September 8 - 12, 2025 Hilton Baltimore Inner Harbor Baltimore, Maryland
Pages:	3522 - 3536
Cite this article:	Kim, Kihyun, Kim, Donguk, Kim, O-Jong, "Operational Scheduling and Analysis of Ground Segment for Regional LEO-PNT Architecture," Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 3522-3536. https://doi.org/10.33012/2025.20468
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