Primary Celestial Body
Author: Tianjiang Shuo
Website: https://cislunarspace.cn
Definition
The nearest large celestial body used as the observation reference in celestial navigation. For near-Earth orbit navigation, the primary body defaults to Earth, but spacecraft near libration points can choose between two large bodies (Sun and Earth) due to their unique spatial position. The paper finds that the choice of primary body significantly affects navigation accuracy: L2 is about 1.5 million km from Earth and about 150 million km from Sun; using Earth yields a much larger starlight angle span and navigation accuracy one order of magnitude better. The conclusion is to select the large body closest to the spacecraft as the primary body.
Application Value
This term在cislunar space missions中has important application value. In orbit design, it can be used foroptimizing transfer trajectories, reducing mission fuel consumption. In attitude control and dynamics analysis, it helps understandthe motion characteristics of spacecraft in complex gravitational fields, providing theoretical support for mission planning. In navigation and orbit determination, methods based on this termcan improve orbit prediction accuracy, supporting the development of autonomous navigation algorithms.
Related Concepts
- Clock Bias
- Apparent Diameter
- Core Spacecraft
- Code Pseudo-range
References
- 赵书阁 等 - 2013 - 日地系统L2点Halo轨道自主天文导航及精度分析