Long-term evolution of navigation satellite orbits: GPS/GLONASS/GALILEO

Abstract

A recent study was performed to examine whether long-term growth in the eccentricity evolution exists for the disposal orbits of navigation satellite systems such as GPS, GLONASS, and GALILEO. Previous studies examined the orbit stability for GPS Block II satellites. The orbits of the non-operational GPS Block I satellites are included in this study because they are at 63.4° inclination, which is different from GPS Block II. Similar to earlier studies, long-term perturbations and stability of these orbits are understood through analytical and numerical investigations. Initially near circular, these types of orbits may evolve into orbits with large eccentricity (as much as 0.7 over 150 years). Analytical approximations through doubly-averaged equations reveal that the cause is due to the resonance induced by Sun/Moon and J 2 secular perturbations. A total of 105 non-operational GLONASS satellites and upper stages and 10 GPS/Block I satellites were propagated for 200 years. Results show that the GLONASS satellites will start to enter the operating GPS constellation after 40 years. The uncovered resonance effect is strongly dependent on orbit inclination and altitude. The effect becomes more pronounced for GALILEO orbits due to their higher altitude, 3000 km above GPS. Strategies to minimize the significant eccentricity growth are identified in this study. These results directly impact the safety of future navigation satellites in the altitude region from 19,000 to 24,000 km. The dependence on initial inclination may help the designers of GPS III and GALILEO systems select the proper inclination for minimizing the large eccentricity growth. The maximum eccentricity growth for GPS and GALILEO can be significantly reduced by selecting operational inclinations a few degrees from the current nominal values for both programs.