Orbit Determination And Error Analysis With Space And Ground Cooperation For LEO Space Surveillance

Within the confines of the territory, the space-based sensors should be explored and demonstrated while the ground-based sensors are developed to improve the space surveillance system for low earth orbit (LEO). Assumed that the space-based radar (SBR) net cooperates with the ground-based radar (GBR) for LEO surveillance, the thesis investigates the site arrangement, error propagation and differential correction with observations from SBRs.The criterion for choosing the site of the GBR is presented. The analysis of the positioning precision about the GBR with multi-bases shows that the optimal arrangement is symmetrical in geometry if the numbers of the auxiliary sensors is over three. And with the optimal arrangement, the high precision of orbit determination could be achieved only with the range measurements from three or more auxiliary sensors, if the standard deviation of the angle measurements is much worse than that of range measurement.The Covariance Analysis DEscribing function Technique (CADET) is implemented in high-precision orbit prediction to obtain the propagation of the mean vector and covariance supposed that the state is a gaussian variable. Compared with the linear variance equation i.e. matrix Ricatti equation, the quasi-linear approximation technique considers the second order of the partial derivatives of the differential equation with respect to the state vector which is more precise in statistics. According to the simulation, the along-track error in position and the radial error in velocity are dominative during propagation. And the propagating precision is determined by the priori standard deviation and the state noise.The orbit determination algorithm combined with the high-precision orbit propagation and differential correction is presented for the space surveillance with the cooperation of the GBR and the SBRs. In other words the latest estimated mean and covariance are propagated until the time that observations are available. And the predicted mean and covariance at that time as the priori are updated with the observations, then the propagation continues.For the precision of the sparse observational data from SBRs the pre-process based on 3σrule is derived. The simulation shows that the high-precision orbit propagation and update by the extended Kalman filter (EKF) can control the along-track error in position and the radial error in velocity very well. While the cross-track error could not be controlled in whole with the low precision measurement of range rate almost helpless against cross-track error in velocity if the observation is single set. And this could be explained by the Hill equation clearly.When the short-arc dense observational data is used in differential correction, the precision is improved and the cross-error is controlled well in comparison with the sparse data. And when the unscented Kalman filter (UKF) is applied to update, the filter converges quicker and the precision is higher than that of EKF, especially the cross-track error in velocity could be controlled much better.The error propagation resulted from initial deviation could be described by Hill equation to explain the numerical simulation above: the along-track error in position has the linear factor about time so does the radial error in velocity, while the equation of the cross-error is a simple harmonic oscillator. And the initial deviation condition is given by Hill equation to control the error propagation of the TLE generated from the single point. And the condition is consistent with the minimal sum of squares of residuals of the TLE generated from sampling. Also the main divergent factor in initial deviation is separated, which may be operational in selecting TLE.The thesis mainly discusses the error propagation and the orbit determination in space surveillance with the cooperation of the SBRs and the GBR, and the achievement could be some help for the design and the development of the national space surveillance system.