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

Positioning, Navigation and Timing for Space Robotics

Research Question: Can We Set up a GPS-like System for the Moon? 

We are entering a new era of Moon exploration. There are more than forty missions planned within the next decade by ten space agencies, not even counting the efforts of private sector companies like SpaceX and Blue Origin. After more than fifty years since the Apollo program, NASA's Artemis mission will land humans on the Moon including the first woman and first person of color. Exploring the Moon also serves as a crucial stepping-stone for the success of future deep space missions. 

With the increase in 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 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. We are also collaborating with NASA on the Cooperative Autonomous Distributed Robotic Exploration (CADRE) project to send a swam of small rovers to the moon surface in 2024 and a long-range traverse and sample return rover autonomy project for the lunar South Pole–Aitken basin. 

Current Research Team: 

  • Keidai Iiyama 
  • Marta Cortinovis
  • Guillem Casadeus Vila
  • Alana Sanchez
  • Kaila Coimbra   
  • Tara Mina
  • Adam
  • Derek

Related Works: 

  • 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. Abstract submitted.
  • Tara Mina, Keidai Iiyama, and Grace Gao, Passive Lunar Surface Network-Based Orbit Determination and Time Synchronization of the Lunar Satellite Navigation System, Proceedings of the Institute of Navigation GNSS+ conference (ION GNSS+ 2024), Baltimore, MD. Abstract submitted.
  • 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 Approximation Methods to Support Lunar Positioning, Navigation, and Timing Services, Navigation: Journal of the Institute of Navigation. Submitted. [paper]
  • 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] 
  • 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] 
  • 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 Systematic Approach to the Design of Lunar Navigation and Communication System with Time-Transfer from Earth-GPS, 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]