Influence of Ground Station Number and its Geographical Distribution on Combined Orbit Determination of Navigation Satellite

Using combined orbit determination based on satellite crosslink ranging observations, navigation system could greatly reduce the dependence of ground stations. In this paper, a constellation constituted by 24MEO+5GEO+3IGSO was simulated considering the characteristics of the second generation of BD (COMPASS), then corresponding simulated combined orbit resolution has been done using this kind of constellation. We implemented analyses from aspects of different ground station number and geographical distribution to investigate their influence on combined orbit determination (COD). Results show that well-distributed stations around the world do a little better orbit determination performance than that with stations of regional distribution in China. Besides, accuracy could be slightly better than precision of broadcast ephemeris only using just one station inside our country. Nevertheless, increase in the number of stations could not significantly improve the COD accuracy when all stations are located regionally at home, however, it could enhance the stability and reliability of the navigation system.