Feasibility Analysis on the Application of GPS Relative Positioning in LEO Constellations

Although many documents usually used the same term when talking about the relative positioning of satellite formations and that of satellite constellations, they are actually different considering the ratio of the relative range between the satellites to the orbital radius. A certain number of researches have been done on the relative positioning of formation-flying satellites using GPS measurements, while little has been done on that of satellite constellations. However, with the booming of LEO (Low Earth Orbit) communications constellations, relative navigation of satellite constellations should be more attention because relative position information is necessary in constellation deployment and maintenance. This paper discussed the feasibility of using GPS relative positioning to determine the relative positions of LEO constellations (altitude within 500 similar to 1500km). In detail it was to analyze the number of the mutual GPS satellites visible to two LEO constellation satellites at the same epoch (in this paper the minimum number above which GPS relative positioning can be used was set to 5). Softwares developed by the institute were used to produce the RINEX observation data, which was then processed with MATLAB programs to get the number of the common visible GPS satellites. Results indicate that using GPS to obtain the relative position information of LEO constellations is feasible, but it is subjected to the elevation angles of the receivers and the satellite number of the constellation. Orbit inclination and orbit altitude also have some influence.