# Summary of Lunar Constellation Navigation and Orbit Determination Technology
## 2 Current Status of Lunar Relay Navigation Satellite Networks
### China's Lunar Navigation and Communication Plan  
The general goal of China's Queqiao comprehensive constellation construction is to build a communication and navigation system that serves the lunar surface, lunar orbit, cislunar space and even deep space by 2045, and expand to the lunar Internet to support unmanned/manned lunar, and even deep space, exploration as cislunar space infrastructure. At the same time, it will support the construction of the Earth-Moon space economic zone, laying a technical foundation for the further construction of the interplanetary Internet and the realization of space power in the future.  
The construction of the entire lunar communication and navigation system has been divided into three phases [18]:  
1. Phase I of the project (around 2030): Build a pilot constellation to support the fourth phase of the lunar exploration project, the international lunar scientific research station and other tasks.
2. Phase II of the project (before 2040): Complete the basic constellation to realize regional navigation. It will serve manned lunar exploration, international lunar exploration, as well as the exploration of Mars and Venus.
3. Phase III of the project (before 2050): Build an expanded constellation to achieve communication and navigation coverage on Mars and Venus, and serve the exploration of Mars, Venus, giant planets and the edge of the solar system.  
Table 1 contains information on the current status of relay navigation satellite constellations, and introduces the leading institutions, project goals, navigation communication criteria and orbits of different constellations. The result shows that by deploying relay satellites in the cislunar space or lunar orbit, continuous coverage of navigation and communications for specific areas of the lunar surface or even the entire lunar surface can be effectively achieved, and the corresponding criteria can be achieved as well. In the future, the relay satellite network will be further applied in lunar exploration missions.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Project Name**} & **Leading** & **Project** & **Navigation** \\  & **Institution** & **Objectives** & **Communication Criteria** \\ \hline \multirow{4}{*}{LunaNet} & \multirow{4}{*}{NASA} & A flexible and scalable & \multirow{4}{*}{Providing network services, positioning, navigation and timing services, and scientific utilization services near the Moon} \\  & & & \\  & & & \\ \cline{3-4}  & & Real-time relay optical & \\ \cline{3-4}  & & laser communications & \\ \cline{3-4}  & & between the Moon and Earth & \\ \hline \multirow{4}{*}{Moonlight} & \multirow{4}{*}{ESA} & Establishing a lunar & \multirow{4}{*}{For manned missions, the target positioning accuracy at any location on the Moon can reach less than 50 m.} \\  & & shared communication & \\ \cline{3-4}  & & and navigation & \\ \cline{3-4}  & & network & \\ \hline \multirow{4}{*}{Lunar Pathfinder} & \multirow{4}{*}{ESA} & \multirow{4}{*}{For unmanned exploration missions} \\  & & The first dedicated & 1: Achieve 100 m positioning accuracy \\ \cline{3-4}  & & navigation and & \\ \cline{3-4}  & & communication & \\ \cline{3-4}  & & satellite of Project & \\ \cline{3-4}  & & Moonlight & \\ \cline{3-4}  & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Analysis of the current status of relay navigation satellite.