Abstract: The study investigates the high-precision application requirements of spacetime reference systems in lunar-Earth space exploration, aiming to evaluate the impact of different spacetime reference systems on the determination of target orbits in lunar-Earth space. Typical orbits within lunar-Earth space are selected as the subjects for quantitative assessment. A comparison strategy for the influence of spacetime reference systems is established. Differences in observational modeling under the frameworks of the Geocentric Celestial Reference System (GCRS) and Barycentric Celestial Reference System (BCRS) are analyzed. Simulation techniques are employed to further explore the specific impacts of these two spacetime reference systems on the determination of target orbits in lunar-Earth space. The results indicate that, under different spacetime reference systems, the modeling differences for ground-based ranging and time delay are less than 4cm, and velocity measurement differences are less than 0.5mm/s. The impact of orbit determination biases remaines within 1m. Modeling differences for inter-satellite bidirectional links are on the centimeter scale, whereas modeling differences for unidirectional links can reach 10m. For lunar-Earth space target orbit determination tasks requiring accuracy at the decimeter level, the application of GCRS is sufficient to meet demands. However, for achieving higher precision in orbit determination, particularly in constructing and maintaining high-precision spacetime benchmarks in lunar-Earth space, as well as utilizing inter-satellite unidirectional link data, the adoption of the BCRS is more appropriate.

Key words: cis-lunar space, spacetime reference system, observational modeling, orbit calculation, precision analysis