Stanford
Navigation and Autonomous Vehicles Lab
Navigation and Autonomous Vehicles (NAV) Lab

Lunar Communication and Navigation Satellite Systems

Lunar communication and navigation satellites orbit the moon.

Research Question: How can we make a complete GPS for the moon?

We are entering a new era of Moon exploration with 200+ planned missions across 10 space agencies and even more private sector companies. With increased human and robotic exploration, we must provide Position, Navigation, and Timing (PNT) services anywhere on the Moon. Current vision-based methods work poorly in the Moon's polar regions and not at all in the darkness of its night and permanently shadowed craters. We must also enable wireless network communication (e.g., cellular or Wi-Fi) on the Moon to support interactions among a large number of assets on the Moon.

On Earth, the Global Positioning System (GPS) provides not only positioning and navigation but also timing and synchronization for cellular communications. Can we set up a GPS-like system for the Moon at a much lower cost? In this way, we can achieve better PNT services, as well as wireless network communication on the Moon, like what we currently have on Earth.

We are creating technologies for a "Moon-GPS," a lunar satellite navigation system with smaller satellites, perhaps as small as a shoe box, compared to existing Earth-GPS satellites which are as large as a truck. The lunar navigation satellites can function with clocks that are a thousand times cheaper than the atomic clocks on today's GPS satellites. The key idea is that the lunar satellite navigation system will listen to signals already broadcast by the Earth-GPS and process those signals to perform timing and ephemeris corrections. Moreover, the legacy GPS codes are based on linear shift feedback registers, which were designed decades ago before personal computers. Powered by recent advances in machine learning, optimization, and computing, we explore new opportunities for developing high-quality spreading signal families.

Current Research Team: 

  • Keidai Iiyama
  • Guillem Casadesus Vila
  • Kaila Coimbra

Related Works: 

  • Keidai Iiyama and Grace Gao, GNSS-based Lunar Orbit and Clock Estimation With Stochastic Cloning UD Filter, Journal of Guidance, Control, and Dynamics, Submitted. [paper]
  • Keidai Iiyama and Grace Gao, Ephemeris and Almanac Design for Lunar Navigation Satellites, IEEE Transactions on Aerospace and Electronic Systems, Submitted. [paper]
  • Keidai Iiyama and Grace Gao, Ionospheric and Plasmaspheric Delay Characterization for Lunar Terrestrial GNSS Receivers with Global Core Plasma Model, NAVIGATION: Journal of the Institute of Navigation, Submitted. [paper]
  • Keidai Iiyama and Grace Gao, Trade-off Analysis for Lunar Augmented Navigation Service (LANS) Constellation Design, NAVIGATION: Journal of the Institute of Navigation, Submitted. [paper]
  • Keidai Iiyama and Grace Gao, Constellation Design and Staged Development for the Lunar Navigation Satellite System, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2025), Baltimore, MD, Sep 2025. [paper] [slides]
  • Keidai Iiyama and Grace Gao, Ionospheric and Plasmaspheric Delay Characterization and Mitigation Methodologies for Lunar Terrestrial GNSS Receivers, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2025), Baltimore, MD, Sep 2025. Best Presentation of the Session Award. [paper] [slides]
  • Guillem Casadesus Vila and Grace Gao, Moon Surface Station to Support Lunar Positioning, Navigation, and Timing Services, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2025), Baltimore, MD, Sep 2025.  [paper] [slides]
  • Alan Yang, Tara Mina, and Grace Gao, Spreading Code Sequence Design via Mixed-Integer Convex Optimization, Navigation: Journal of the Institute of Navigation. September 2025, 72 (3); DOI: 10.33012/navi.706. [paper]
  • Kaila M. Y. Coimbra, Marta Cortinovis, Tara Mina, and Grace Gao, Single-Satellite Lunar Navigation via Doppler Shift Observables for the NASA Endurance Mission, Navigation: Journal of the Institute of Navigation. September 2025, 72 (3); DOI: 10.33012/navi.710. [paper]
  • Guillem Casadesus Vila and Grace Gao, Sensor Fusion for Autonomous Orbit Determination and Time Synchronization in Lunar Orbit, IEEE Aerospace Conference, Big Sky, MT, March 2025. Best Paper of the Track Award. [paper] [slides]
  • Kaila M. Y. Coimbra and Grace Gao, Comparative Analysis and Design of a Dual-Satellite System for Lunar Rover Localization, IEEE Aerospace Conference, Big Sky, MT, March 2025. [paper] [slides]
  • Guillem Casedesus Vila, Keidai Iiyama, and Grace Gao, LuPNT: An Open-Souce Simulator for Lunar Communications, Positioning, Navigation, and Timing, IEEE Aerospace Conference, Big Sky, MT, March 2025.  [paper] [slides]
  • Keidai Iiyama, William W. Jun, Sriramya Bhamidipati, Grace Gao, and Kar-Ming Cheung, Orbit Determination and Time Synchronization for the Future Mars Relay and Navigation Constellation, IEEE Aerospace Conference, Big Sky, MT, March 2025. [paper] [slides]
  • Keidai Iiyama, Daniel Neamati, and Grace Gao, Autonomous Constellation Fault Monitoring with Inter-satellite Links: A Rigidity-Based Approach, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2024), Baltimore, MD, Sep 2024. Best Presentation of the Session Award. [paper] [slides]
  • Kaila M. Y. Coimbra, Marta Cortinovis, Tara Mina, and Grace Gao, Single-Satellite Lunar Navigation via Doppler Shift Observables for the NASA Endurance Mission, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2024), Baltimore, MD, Sep 2024. [paper] [slides]
  • Guillem Casadesus Vila and Grace Gao, Markov Decision Processes for Scheduling Lunar PNT Services, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2024), Baltimore, MD, Sep 2024. [paper] [slides]
  • Alan Yang, Tara Mina, Stephen Boyd, and Grace Gao, Large-Scale GNSS Spreading Code Optimization, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2024), Baltimore, MD. [paper] [slides]
  • Alan Yang, Tara Mina, and Grace Gao, Spreading Code Optimization for Low-Earth Orbit Satellites via Mixed-Integer Convex Programming, EURASIP Journal on Advances in Signal Processing. May 2024; DOI 10.1186/s13634-024-01160-0. [paper]
  • Adam Dai, Shubh Gupta, and Grace Gao, Neural Elevation Models for Terrain Mapping and Path Planning, RoboNeRF: 1st Workshop on Neural Fields in Robotics at ICRA 2024, May 2024. [paper]
  • Marta Cortinovis, Tara Mina, and Grace Gao, Assessment of Single Satellite-based Lunar Positioning for the NASA Endurance Mission, IEEE Aerospace Conference, Big Sky, MT, March 2024. [paper]
  • Keidai Iiyama*, Guillem Casadesus Vila*, and Grace Gao, Contact Plan Optimization and Distributed State Estimation for Delay Tolerant Satellite Networks, IEEE Aerospace Conference, Big Sky, MT, March 2024. [paper]
  • Marta Cortinovis, Keidai Iiyama, and Grace Gao, Satellite Ephemeris Parameterization Methods to Support Lunar Positioning, Navigation, and Timing Services, Navigation: Journal of the Institute of Navigation. December 2024, 71 (4) ; DOI: 10.33012/navi.664. [paper]
  • Keidai Iiyama, Sriramya Bhamidipati, and Grace Gao, Precise Positioning and Timekeeping in Lunar Orbit via Terrestrial GPS Time-Differenced Carrier-Phase Measurements, Navigation: Journal of the Institute of Navigation. March 2024, 71(1); DOI: 10.33012/navi.635. [paper]
  • Alan Yang, Tara Mina, and Grace Gao, Fast Spreading Code Optimization Under Doppler Effects, ION International Technical Meeting (ION ITM 2024), Long Beach, CA, Jan 2024. [paper]  [slides] [video]
  • Sriramya Bhamidipati, Tara Mina, Alana Sanchez, and Grace Gao, Satellite Constellation Design for a Lunar Navigation and Communication System, Navigation: Journal of the Institute of Navigation. Dec 2023, 70 (4) navi.613; DOI: 10.33012/navi.613. [paper] [video]
  • Sriramya Bhamidipati, Tara Mina and Grace Gao, A Case Study Analysis for Designing a Lunar Navigation Satellite System with Time-Transfer from Earth-GPS, Navigation: Journal of the Institute of Navigation. Dec 2023, 70 (4) navi.599; DOI: 10.33012/navi.599. [paper] [video]
  • Marta Cortinovis, Keidai Iiyama, and Grace Gao, Satellite Ephemeris Approximation Methods to Support Lunar Positioning, Navigation, and Timing Services, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2023), Denver, CO, Sep 2023. Best Presentation of the Session Award. [paper] [slides] [video]
  • Keidai Iiyama*, Guillem Casadeus Vila*, and Grace Gao, LuPNT: Open-Source Simulator for Lunar Positioning, Navigation, and Timing, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2023), Denver, CO, Sep 2023.   [paper] [slides] [code]
  • Keidai Iiyama, and Grace Gao, Positioning and Timing of Distributed Lunar Satellites via Terrestrial GPS Differential Carrier Phase Measurements, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2023), Denver, CO, Sep 2023. [paper] [slides]
  • Tara Mina, Alan Yang, and Grace Gao, Designing Long GPS Memory Codes Using the Cross Entropy Method, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2023), Denver, CO, Sep 2023. [paper] [slides] [video]
  • Alan Yang, Tara Mina, and Grace Gao, Spreading Code Sequence Design is a Convex Optimization Problem with Binary Constraints, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2023), Denver, CO, Sep 2023. [paper] [slides] [video]
  • Alan Yang, Tara Mina, and Grace Gao, Binary sequence set optimization for CDMA applications via mixed-integer quadratic programming, IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) 2023. [paper]
  • Adam Dai, Shubh Gupta, and Grace Gao, Neural Radiance Maps for Extraterrestrial Navigation and Path Planning, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2023), Denver, CO, Sep 2023. [paper] [slides] [video]
  • Isabella Torres and Grace Gao, Intent- and Fault-based Trajectory Prediction for Cooperative Localization and Collision Avoidance in Swarms, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2023), Denver, CO, Sep 2023. [paper] [slides] [video]
  • Sriramya Bhamidipati, Tara Mina and Grace Gao, Lunar Navigation: A Case-Study Analysis, Inside GNSS Magazine, Nov-Dec 2022. Cover Story. [pdf]
  • Keidai Iiyama, Sriramya Bhamidipati, and Grace Gao, Terrestrial GPS Time-Differenced Carrier-Phase Positioning of Lunar Surface Users, IEEE Aerospace Conference 2023. [paper] [slides]
  • Keidai Iiyama, Sriramya Bhamidipati, and Grace Gao, Precise Positioning and Timekeeping in Lunar Orbit via Terrestrial GPS Time-Differenced Carrier-Phase Measurements, Proceedings of the Institute of Navigation ITM conference (ION ITM 2023), Long Beach, CA, Jan 2023. [paper] [slides]
  • Tara Mina and Grace Gao, Designing Low-Correlation GPS Spreading Codes with a Natural Evolution Strategy Machine Learning Algorithm, Navigation: Journal of the Institute of Navigation. vol. 69, no. 1, Mar. 2022. doi: 10.33012/navi.506. [paper][video]
  • Sriramya Bhamidipati, Tara Mina and Grace Gao, Time Transfer from GPS for Designing a SmallSat-Based Lunar Navigation Satellite System, Navigation: Journal of the Institute of Navigation. Sep 2022, 69 (3) navi.535; DOI: 10.33012/navi.535. [paper] [video]
  • Sriramya Bhamidipati, Tara Mina, Alana Sanchez and Grace Gao, A Lunar Navigation and Communication Satellite System with Earth-GPS Time Transfer: Design and Performance Considerations, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2022), Denver, CO, Sep 2022. Best Presentation of the Session Award. [paper] [slides] [video]
  • Alana Sanchez and Grace Gao, Relativistic Time Transfer Error Correction for a Lunar Navigation Satellite System, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2022), Denver, CO, Sep 2022. [slides] [video]
  • Sriramya Bhamidipati, Keidai Iiyama*, Tara Mina* and Grace Gao, Time-Transfer from Terrestrial GPS for Distributed Lunar Surface Communication Networks, IEEE Aerospace Conference 2022. [paper] [slides]
  • Sriramya Bhamidipati, Tara Mina and Grace Gao, A Case Study Analysis for Designing a Lunar Navigation Satellite System with Time-Transfer from Earth-GPS, Proceedings of the Institute of Navigation ITM conference (ION ITM 2022), Long Beach, CA, Jan 2022. [paper] [slides] [video]​​​
  • Sriramya Bhamidipati, Tara Mina and Grace Gao, Design Considerations of a Lunar Navigation Satellite System with Time-Transfer from Earth-GNSS, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2021), St. Louis, MO, Sep 2021. Best Presentation of the Session Award. [paper] [slides] [video]
  • Tara Mina and Grace Gao, Designing Low-Correlation GPS Spreading Codes via a Policy Gradient Reinforcement Learning Algorithm, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2020), St. Louis, MO, Sep 2020. Best Presentation of the Session Award. [paper] [slides] [video]
  • Tara Mina and Grace Gao, Devising High-Performing GPS Pseudo-Random Noise Codes Using Evolutionary Learning Algorithms, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2019), Miami, FL, Sep 2019. Best Presentation of the Session Award. [paper] [slides]