Real-time relative orbit estimation of noncooperative space target based on nonlinear filtering

The problem of real-time relative orbit estimation of long range and high speed between a noncooperative target and a chaser is addressed. A high precision relative orbit model, in which the Earth J2 perturbation has been taken into consideration, is established for state estimation. As the attitude of the chaser is required for relative orbit estimation, it has also been estimated. The range, elevation, and azimuth between the target and the chaser, which can be measured by a laser rangefinder and a CCD device, are chosen as measuring vector, while a rate gyroscope and one star sensor is installed on the chaser to measure its rate and attitude parameters. On the basis of nonlinear filtering technology, two kinds of filtering systems are designed, namely the separated filtering system and the united filtering system, and the relationship between the two filtering systems are analyzed. Simulation results indicate the united filtering system is more robust than the separated filtering system against realistic initial attitude errors and attitude measurement noises.