Nonlinear method for parameter identification applied to a trajectory estimation problem

The trajectory estimation problem is formulated as a parameter identification problem. The performance index is that of weighted least squares, and the unknown parameters are the initial conditions of the trajectory and the parameters which are used to represent the aerodynamic constants or functions. The optimization problem is solved using a square-root variable-metric algorithm. The derivatives needed by the optimization algorithm are computed numerically. Finally, the nonlinear equation method is used to compute the initial state and drag coefficient history of a reentry vehicle using simulated radar data.