Ground-Assisted Position Navigation and Timing (PNT) for Moon and Mars

The recent exploration initiatives for robotic and human missions to the Moon and Mars require long-term communications and navigation infrastructures that provide accurate and autonomous PNT services for orbiting and surface users. NASA launched the Lunar Communication Relay and Navigation System (LCRNS) project in 2022 to meet the needs of the Artemis missions and other lunar missions. ESA, JAXA, other space agencies, and commercial entities may contribute additional lunar relay orbiters that are compatible with the NASA's orbiters via the LunaNet Interoperability Specifications.To ensure sustained human presence at the Moon, NASA plans to deploy surface infrastructure elements that can survive the lunar nights. We are investigating the operation concept and PNT performance of augmenting the lunar relay network with a surface station with the following capabilities: 1. Provide short-range time distribution to orbiting and surface spacecraft. 2. Transmit a GNSS-like signal to augment the orbital determination (OD) schemes of lunar spacecraft for fast OD convergence. The transmitter can also act as a surface beacon that guides the lunar spacecraft during dynamic events like decent and ascent. 3. Receive lunar relay orbiter's and Earth's GPS signals and estimate corrections for orbiting spacecraft. This enables improved OD performance and accurate relative navigation of users on the lunar surface. The Joint Doppler Ranging (JDR) method requires as few as one orbiter to perform a real-time position fix of a surface user. This is particularly useful during the early stage of lunar relay network deployment when the number of orbiters is small.The lunar surface station architecture is directly applicable to the Mars relay network, and this supports the NASA Moon-to-Mars initiative.