Precision Onboard Navigation for LEO Satellite based on Precise Point Positioning

The PPP is a technique being actively researched and developed for estimating the precise position of a stationary point on the surface of the earth. Its particular features are that unlike the relative positioning method, the PPP does not require reference points and it provides the centimeter-level positioning accuracy in real-time using the precise orbit and clock information of the navigation satellites such as the GPS satellites. Lately, the application of the PPP technique to the onboard navigation of the low earth orbit (LEO) satellites is attracting attentions from aerospace researchers and engineers. Such a navigation technique is called the PPP in Space or the Space PPP. As for the existing approaches, the PPP in Space methods using precise LEO satellite dynamics [1] and kinematic PPP which does not use such dynamics [2] [3] were proposed and these results were impressive: the decimeter-level or even the centimeter-level satellite positioning accuracy was confirmed by the offline experiments using actual European LEO satellites dataset. Although these navigation methods are obviously stateof-the-art, this paper takes an another approach that focuses on improving the accuracy of satellite onboard navigation (NAV) using the PPP technique. The methodology presented in this paper is similar to the work [4] that used a reference orbit trajectory for the PPP in Space, that is, the errors of the reference trajectory were estimated using the PPP technique. However, the calculation of their reference trajectories requires the computational time and it can not be performed onboard a satellite. Therefore, we designed our method to work in realtime by using the onboard NAV as the reference trajectory. The performance of the proposed PPP NAV method was evaluated using the actual data of a Japanese earth observation satellite ALOS2 (Advanced Land Observing Satellite) [5].