Benjamin Johnis, Sanjeev Gunawardena, Air Force Institute of Technology; Avinash Agrawal, Draper

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The United States Cislunar Technology Strategy Working Group published the National Cislunar Science and Technology Strategy in 2022. Executive department representatives used a whole-of-government approach to address unique national challenges associated with the proliferation of human space exploration to the Moon and beyond. One of the four objectives is to "implement cislunar communications and navigation capabilities with scalable and interoperable approaches to enable a cooperative and sustainable ecosystem in cislunar space." (National Science and Technology Council, 2022) Humans will return to the Moon in 2025 under the National Aeronautics and Space Administration (NASA) Artemis mission, increasing the risk of space isolation and driving the demand for Department of Defense collaboration to rescue astronauts in distress. The NASA Search and Rescue Mission Office requires Position, Navigation, Timing (PNT) services to report and locate cislunar contingencies to enable rapid response capabilities in the future. This study examines recent cislunar PNT literature and experiments to recommend a satellite-based architecture for the rescue requirement, including Lunar Navigation Satellite System Receiver designs for prototyping development. The receiver design uses PyChips and Python-based software with modified Global Navigation Satellite System (GNSS) settings to adjust for lunar signal specifications defined by NASA (Gunawardena, 2021). The optimal prototyping configurations are based on power-to-channel trade-offs and user needs. The Air Force Research Lab, in conjunction with the Air Force Institute of Technology and Draper Laboratory, modeled a theoretical Cislunar Autonomous Navigation Satellite System (CLASS) to augment earth based GNSS services. The optimal satellite orbits are based on suitable geometries to NASA Artemis operational areas, cislunar activities, and cost-benefit analysis findings gained through previous experiments. The geometric dilution of precision and simulated almanac is predicted by modeling desirable satellite vehicle orbits. This information is ingested into the receiver for software experimentation. The architecture design includes a space segment in Lunar and Lagrange orbits, a ground segment on the lunar surface, and a lunar surface user segment. The ground segment provides users the satellite positions negating the exhaustive task of satellite vehicle error calculations through ephemeris decryption. The receiver design outputs data for ranging the user position in concert with the National Geospatial Agency’s lunar reference frame. The project provides a comprehensive analysis for immediate design implementation, prototyping, and experimentation to meet U.S. government needs in line with the national science and technology strategy.