First In-Orbit Demonstration of Real-Time Precise Orbit Determination for LEO Satellite Using QZSS MADOCA-PPP

Saya Matsushita, Toshitaka Sasaki, Hideki Yamada, Keito Yoshida, Tatsuya Nagano, Satoshi Kogure

Peer Reviewed

Abstract:	Quasi-zenith satellite system (QZSS) provides highly precise positioning augmentation services, named Multi-Global Navigation Satellite System Advanced Orbit and Clock Augmentation - Precise Point Positioning (MADOCA-PPP), which consists of satellite orbit and clock correction through L6 signals. Precise point positioning (PPP) using this augmentation data realizes centimeter-level positioning accuracy in real-time on the ground. Applying this technology to future low earth orbit (LEO) satellites will enable real-time Precise Orbit Determination (POD) onboard the satellites. Japan Aerospace Exploration Agency (JAXA) has developed a POD tool that calculates PPP of LEO satellites in real-time using MADOCA-PPP by modifying a ground-based PPP software. This algorithm has been demonstrated on a LEO satellite for one year starting in 2025. During the initial checkout of the satellite, an onboard PPP demonstration unit consisting of GNSS receivers, antennas, amplifiers, an onboard computer, and a corner-cube reflector was confirmed to perform normally, and approximately 12 hours of GNSS data were acquired. Therefore, we conducted the first long-term onboard PPP accuracy evaluation using the acquired data. Due to the limited visibility of QZSS, LEO satellites are inevitably unable to receive real-time MADOCA-PPP, and the navigation performance during such QZSS invisible periods must be carefully assessed. This study evaluates alternative onboard navigation strategies for maintaining accurate orbit determination during QZSS invisible periods, focusing on the use of broadcast ephemerides and ultra-rapid ephemerides as substitute orbit and clock information. The results show that PPP using broadcast ephemerides achieved positioning accuracy of approximately 20 cm (3DRMS), demonstrating the feasibility of fully autonomous onboard navigation without external correction data. In contrast, when ultra-rapid ephemerides estimated from recent observation data were applied during QZSS-invisible periods, the positioning accuracy improved to under 15 cm (3DRMS). These results provide an initial validation that MADOCA-PPP is a promising and effective approach for real-time high-precision orbit determination of LEO satellites.
Published in:	Proceedings of the ION 2026 Pacific PNT Meeting April 13 - 16, 2026 Hilton Waikiki Beach Honolulu, Hawaii
Pages:	166 - 176
Cite this article:	Matsushita, Saya, Sasaki, Toshitaka, Yamada, Hideki, Yoshida, Keito, Nagano, Tatsuya, Kogure, Satoshi, "First In-Orbit Demonstration of Real-Time Precise Orbit Determination for LEO Satellite Using QZSS MADOCA-PPP," Proceedings of the ION 2026 Pacific PNT Meeting, Honolulu, Hawaii, April 2026, pp. 166-176. https://doi.org/10.33012/2026.20614
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