Abstract: A least square estimation method for determining spacecraft position in earthmoon transfer orbit was presented based on angle observations between three stars and two near celestial bodies. Due to relative low accuracy of the above method, the genetic algorithm was used to solve the spacecraft position equations based on the moon and stars celestial information observations and obtained a re-positioning of the spacecraft by using planetary sensors to measure the geometric relationship among the spacecraft, the moon, the earth, and using the star sensors to identify the stars. Simulation results show the method can greatly improve the navigation accuracy. 

Key words: Genetic algorithm, Pure star navigation, Earth-moon transfer orbit, Least square method, Location simulation, Spacecraft