TLE data based precise estimation of satellite's orbital parameters

Satellite orbits are usually estimated by employing a filter system model whose state variables are the position and the velocity defined on the earth-fixed inertial (ECI) rectangular coordinate system. However, this filter formulation causes estimation errors due to nonlinearity of the measurement if the two-line element (TLE) data in which satellite's information is provided by orbital parameters. In this paper, we propose a filtering method by adopting orbital parameters as state variables to use TLE data directly. Here, we introduce Kozai's equations of orbital motion including gravitation perturbation terms for the propagation model so that more precise orbit determination can be possible. The performance of the proposed filter is verified via numerical simulations.