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A novel simplified parametric model for long-duration impulsive orbit rendezvous is proposed. Based on an existing fast estimation method, the optimal impulses and trajectory can be expressed by only ten parameters whose initial values can be easily determined.Then, these parameters are used to predict orbital deviations with a target orbit. A simple correction process is designed to sequentially update the parameters based on the J2 perturbed analytical dynamic equations of circular orbits. Finally, an iteration loop is formed to obtain the precise parameters and optimal trajectory. The simulation results confirm that the simplified parametric optimization method can be applied to elliptical orbits of small eccentricity and adapts well to both analytical and high-precision dynamics.The deviations could always converge within five iterations and the calculation was more efficient than the existing methods.

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Strategy of autonomous optical navigation for Mars-approaching phase and its semi-physical simulation method were studied. First, the dynamics model was set up based on the reference orbit preliminarily designed in a Mars exploration mission. Second, the observation model and an EKF filtering algorithm were developed. Then, a semi-physical simulation system was founded including five modules: an orbit producer, a Mars simulator, a camera system, an autonomous optical navigation module and a display module. The position and velocity were solved using simulated observation data, and the results of several deferent conditions were listed. Influence of initial orbit error and camera parameters were analyzed, which validated the practicability of the simulation system.