Abstract. Using high precision laser ephemeris as reference, the precision of orbit prediction is analyzed of an analytical model which is formulated by quasi-analytical average method. The result shows that: the orbit prediction accuracy of MEO and LEO satellites is several hundred meters in 1 day and not more than 10km in 7 days. The position error changes quickly over time. The calculation speed is fast using the analytical model. It can be used for precise orbit determination for a short term about 1 or 2 days. And it also can be used for the general accuracy of the long-term orbit prediction. But if the prediction time is too long, the accuracy will drop sharply.
The localisation of a stationary emitter with several separated sensors is studied. At low signal-to-noise ratio, the direct position determination (DPD) approach is more precise than the two-step method which estimates the time difference of arrival (TDOA) first and locates the emitter by the TDOAs. However, the exhaustive search is usually employed to find the global maximum since the object function of DPD is non-convex. After analysing the characteristics of the object function, a DPD with improved particle filter and gradient descent method (GDIPF-DPD) is proposed. The initial and fine estimations are provided by the IPF and GD methods, successively, as the object function has single peak around the expected position and is differentiable. The IPF decreases the times of resampling through mapping the particle weights before normalisation into 0-1. The GD method improves the accuracy by seeking within the single peak. Furthermore, the position Cramér-Rao lower bound of DPD with attenuation coefficient is derived and proved to be consistent with the two-step method of TDOA. Simulation results indicate that the position accuracy of the proposed algorithm is equivalent with grad search method and its computation cost is less by two orders of magnitude.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.