Initial state estimation for boost phase object based on 8-state gravity turn model using pseudo-linear estimator

For space-based bearing-only observations, the initial state estimation of the boost phase object is the solution to the nonlinear Least squared estimation (LSE) problem. This paper transformed the nonlinear problem into a linear LSE problem using the linearization of the bearing-only measurement and the target trajectory, which facilitated the direct estimation of initial state whilst avoiding to use the Gauss-Newton iteration. In particular, the explicit derivation of the pseudo-linear measurement and its statistical moments are deduced, which helped to determine the applying conditions of the proposed method. The numerical simulations illustrated the advantage of the proposed method with respect to precision and efficiency.