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Session E1: Cislunar, Lunar, and Martian Positioning, Navigation, and Timing 1

Japan's LNSS Demonstration Mission Updates: Technical Progress, Development and Policy Frameworks
Toshihiro Shibukawa, Kota Kakihara, Shogo Matsuo, Joshua Critchley-Marrows, Sophie Kippen, Takeshi Ono, Takasu Tomoji, Osamu Arai, ArkEdge Space Inc.
Date/Time: Wednesday, Sep. 16, 8:57 a.m.

In recent years, many initiatives and activities have been launched globally to accelerate lunar exploration and future settlement plans in the vicinity of the Moon. For example, the Artemis program, which is the overarching program of the United States and its partners, includes crewed lunar landings by the Orion spacecraft and the construction of a lunar-orbiting crewed station called Gateway [1]. The launch of the Artemis II mission, which will be the first crewed lunar mission in more than 50 years, is projected as early as April 2026 [2]. In Japan, JAXA has been working on several lunar exploration activities such as SLIM [3] and LUPEX [4], and also has played a key role in developing the Global Exploration Roadmap (GER), a long-term exploration plan of the Moon and the solar system [5]. Japan has also been contributing to the Artemis program, mainly through the development of the Lunar Cruiser, a crewed pressurized rover that supports crewed exploration activities on the surface of the Moon [6].
As global lunar exploration initiatives accelerate, the demand for reliable Positioning, Navigation, and Timing (PNT) infrastructure in the lunar vicinity has become paramount. Japan’s contribution to this global effort is the Lunar Navigation Satellite System (LNSS) [7, 8], a constellation-based architecture designed to provide PNT services for surface and orbital users, including coverage of the lunar far side. The LNSS initially targets users at the lunar south pole, aiming to provide positioning accuracies in the order of several tens of meters. To provide continuous services, a constellation of 8 to 10 satellites in the Elliptical Lunar Frozen Orbit (ELFO) is required in the LNSS. Considering the high transportation cost to lunar orbit and the fast expansion of exploration activities, the LNSS plans to utilize small satellites in the order of 100 – 200 kg to lower the construction cost of the system and realize a fast launch to operational capability.
Traditional deep-space PNT relies heavily on Earth-based ground stations like the Deep Space Network (DSN); however, the projected surge in lunar activity is expected to surpass the capacity of this terrestrial infrastructure. To address these challenges, the Japanese LNSS architecture utilizes the reception of weak terrestrial GNSS signals to perform autonomous onboard Orbit Determination and Time Synchronization (ODTS). This approach, validated by previous feasibility studies [8] and missions such as LuGRE [9], can realize an ODTS accuracy of several tens of meters, and allows for a PNT system that is significantly less dependent on constant ground station support.
Before commencing development of the entire LNSS system, many key technologies and unknown error sources must be validated and evaluated to prove it to be an effective system. Therefore, prior to Full Operational Capability (FOC) of the LNSS, JAXA has scheduled a demonstration mission of the LNSS. Following three years of conceptual studies with the Japan Aerospace Exploration Agency (JAXA), ArkEdge Space was awarded a contract under the JAXA Space Strategy Fund in November 2024 to lead the full-scale development of the LNSS demonstration satellite and its navigation payload[10].
Targeting a launch in 2029, the demonstration mission consists of a 120 kg-class small satellite and a dedicated receiver on a lunar surface lander. The satellite will operate in a 6-hour circular polar orbit to validate the technical feasibility of the LNSS architecture, including weak GNSS signal tracking and signal-in-space (SIS) dissemination for lunar users.
Technical progress on the navigation payload has advanced significantly, successfully passing the Preliminary Design Review (PDR) and moving into the manufacturing of Engineering Models (EM). The core of the system is the Navigation Computer (NOC), which executes complex ODTS algorithms. To maintain timing stability in the absence of constant ground updates, a high-stability atomic frequency standard is integrated. Furthermore, a high-sensitivity GNSS receiver is being developed to match the mission requirements to extract usable data from GNSS spillover and sidelobe signals. To mitigate the challenges of decoding very weak GNSS signals, the mission implements a Long-Term Ephemeris (LTE) approach, where predicted orbital parameters of GNSS satellites are generated on the ground and uploaded via telecommand links, ensuring a Signal-In-Space Error (SISE) of less than 20 meters for the lunar users.
For the satellite development, ArkEdge Space is leveraging its strengths as a micro-satellite integrator. Based on experience and heritages from past satellite development and operation, such as the EQUULEUS spacecraft [12] which was a secondary payload of the Artemis I mission, the preliminary design of the satellite has been updated, heading towards the PDR of the satellite system in the fall of 2026.
Beyond the internal hardware development, the mission is being designed to align with international interoperability standards, specifically the LunaNet framework [11]. This includes the implementation of the Lunar Augmented Navigation Service (LANS) broadcast within the S-band spectrum. However, this transition toward a multi-user environment introduces complex spectrum management challenges. Technical analysis has identified potential interference from adjacent-band communications, such as 3GPP or Wi-Fi systems used for surface lunar links, which may desensitize PNT receivers. Additionally, there is a critical need to protect the Shielded Zone of the Moon (SZM) for radio astronomy. Current prototype testing shows that the 2nd harmonic emissions of S-band transmitters can overlap with protected C-band frequencies. ArkEdge Space is currently working to improve spurious emission suppression to ensure that the LNSS signals follow the LANS signal format and standards, which will result in avoiding interference with sensitive astronomical observations and other lunar RF operations. Also, the receiver in the demonstration mission will not only receive signals from the LNSS demonstration satellite, but also signals from NASA and ESA lunar PNT systems, such as the LCRNS and LCNS, to demonstrate interoperability within the LunaNet framework.
The ultimate goal of the Japanese LNSS program is to bridge these rigorous technical developments with broader policy and regulatory priorities. Drawing from established international frameworks, such as the maritime VHF Data Exchange System (VDES), ArkEdge Space is advocating for a coordinated global approach to lunar PNT. This involves the publication of policy principles centered on awareness, education, and the use of foundational international references. By integrating advanced aerospace engineering with proactive spectrum diplomacy, the LNSS demonstration mission serves as a cornerstone for a sustainable, interoperable, and peaceful lunar ecosystem.
[1] Creech, S., Guidi, J., & Elburn, D. (2022, March). Artemis: an overview of NASA's activities to return humans to the Moon. In 2022 ieee aerospace conference (aero) (pp. 1-7). IEEE.
[2] BBC (2026, March). When does the Nasa Moon mission launch and who are the Artemis II crew? https://www.bbc.com/news/articles/c0q4w3l0wdvo Accessed March 2nd, 2026.
[3] Sakai, S., Kushiki, K., Sawai, S., Fukuda, S., Miyazawa, Y., Ishida, T., ... & Saito, H. (2025). Moon landing results of SLIM: A smart lander for investigating the Moon. Acta Astronautica, 235, 47-54.
[4] Mizuno, H., Wakabayashi, S., Ohtake, M., Hoshino, T., & Asoh, D. (2024). Development Status in 2024 on Lunar Polar Exploration (LUPEX) Project. In IAF Space Exploration Symposium-Held at the 75th International Astronautical Congress, IAC 2024 (pp. 105-112). International Astronautical Federation, IAF.
[5] The International Space Exploration Coordination Group (ISECG) (2024, August). Global Exploration Roadmap. https://www.globalspaceexploration.org/wp-content/isecg/GER2024.pdf. Accessed March 2nd, 2026.
[6] TOYOTA (July 2024). Lunar Cruiser. https://global.toyota/en/mobility/technology/lunarcruiser/. Accessed March 2nd, 2026.
[7] Murata, M., Kawano, I., & Kogure, S. (2022, January). Lunar navigation satellite system and positioning accuracy evaluation. In Proceedings of the 2022 International Technical Meeting of The Institute of Navigation (pp. 582-586).
[8] Murata, M., Koga, M., Nakajima, Y., Yasumitsu, R., Araki, T., Makino, K., ... & Tanaka, T. (2022, October). Lunar navigation satellite system: Mission, system overview, and demonstration. In 39th International Communications Satellite Systems Conference (ICSSC 2022) (Vol. 2022, pp. 12-15). IET.
[9] Parker, J. J. K., Dovis, F., Anderson, B., Ansalone, L., Ashman, B., Bauer, F. H., ... & Valencia, L. (2022, January). The Lunar GNSS Receiver Experiment (LuGRE). In Proceedings of the 2022 International Technical Meeting of The Institute of Navigation (pp. 420-437).
[10] ArkEdge Space (2024, November). ArkEdge Space Selected by JAXA’s Space Strategy Fund to Lead Lunar Navigation System Development - Advancing Lunar Infrastructure Development to Support the Future Lunar Economy -. https://arkedgespace.com/en/news/2024-11-29_jaxaspacestrategyfund_lnss. Accessed March 2nd, 2026.
[11] NASA (2025, January). LunaNet Interoperability Specification Document Version 5. https://www.nasa.gov/wp-content/uploads/2025/02/lunanet-interoperability-specification-v5-baseline.pdf?emrc=606f95. Accessed March 2nd, 2026.
[12] Funase, R., Kawabata, Y., Nakajima, S., Fuse, R., Sekine, H., & Koizumi, H. (2025, March). EQUULEUS: Artemis-1 CubeSat to successfully demonstrate trajectory control techniques within the Sun?Earth?Moon region to enable future deep space missions by small satellites. In Small Satellites Systems and Services Symposium (4S 2024) (Vol. 13546, pp. 186-193). SPIE.

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