Optimized re-entry time prediction of Molniya orbit objects

To achieve a stable future space environment for carrying out safe operations, the orbital lifetime of any satellite is recommended to be limited to 25 years. Re-entry time estimation is one of the key areas of debris mitigation techniques. Highly elliptical orbits (HEOs) around Earth are one of the most debris populated regions of the space environment. Molniya orbit is a type of HEO, with a period of ~12 hours, and is critically inclined with the swath covering the high latitudinal regions of the Earth. The re-entry times of objects in Molniya orbit should be carefully analyzed to improve future mission analysis techniques. Despite the availability of high fidelity orbit propagators, the uncertainty in the initial parameters can lead to an inaccurate prediction. In this study, the re-entry time prediction of Molniya satellites is carried out as an optimal estimation problem. For carrying out optimal re-entry estimation of Molniya satellites, eccentricity and ballistic coefficient are treated as uncertain parameters. Optimal estimate of the design variables namely eccentricity and ballistic coefficients is determined by using Response Surface Methodology (RSM) and Genetic Algorithm (GA). Using Numerical Prediction of Orbital Events (NPOE) software, the numerical propagation is carried out with realistic perturbation model. By use of this method, accurate re-entry time of six Molniya satellites are predicted with errors less than 5% when compared with actual data.