LuPNT: An Open-Source Simulator for Lunar Communications, Positioning, Navigation, and Timing

The growing focus on missions to the Moon necessitates reliable communication and Positioning, Navigation, and Timing (PNT) services in cis-lunar space. To address the growing research needs in this field, we have been developing LuPNT, a comprehensive, open-source simulation framework that integrates astrodynamics, communication, and PNT functionalities into a single platform. The simulator is developed primarily in C++ for computational efficiency while also featuring Python bindings to facilitate rapid algorithmic development and user interaction. This paper introduces several new features and applications, including new core functionalities, the generation of realistic images for optical navigation, new measurement models including inter-satellite links, a modular state estimation framework, and contact plan design. We demonstrate the capability of the simulator through two different simulation scenarios: Elliptical Lunar Frozen Orbit (ELFO) navigation using side-lobe signals from multiple GNSS constellations, and ephemeris fitting for ELFO. Overall, LuPNT provides a unified, comprehensive tool for lunar PNT and communication research and advances the potential for lunar exploration by enabling the development, integration, and comparison of diverse PNT algorithms within a modular, extensible framework.