Precision propagation and orbit decay predication of low earth orbit satellites

[摘要] ENGLISH ABSTRACT: This study investigates the theory of precision satellite orbit propagation and satellitelifetime prediction and lead to the development of two necessary software tools foranalysis in these fields. Precision propagation was achieved through the implementationof Cowell's method of special perturbations, considering perturbations due to a 70x70asymmetrical gravity field, atmospheric drag, Luni-Solar attraction and Solar radiationpressure. The satellite's perturbed equations of motion were integrated utilizing a seveneighthorder Runge-Kutta-Fehlberg numerical integration procedure, limiting errorpropagation by employing adaptive step size control. The MSlS-90 atmospheric densitymodel, providing for diurnal and semi-annual variations, was employed to determineatmospheric density. Care was taken in the precision modelling of the motion of the12000 equator and equinox. Propagation results for this test case proved to be superior tothe SGP4 propagator and a commercial package.The long-term effects of Earth oblateness and atmospheric drag on a satellite's orbitalelements were investigated and applied to the orbit decay prediction problem. Orbitdecay was predicted by integrating the rates of change of the orbital elements due to Earthoblateness and atmospheric drag. A semi-analytical technique involving Runge-Kuttaand Gauss-Legendre quadrature was employed in the solution process. Relevant softwarewas developed to implement the decay theory. Optimum drag coefficients, estimatedfrom drag analysis using precision propagation, were used in decay prediction. Two testcases of observed decayed satellites were used to evaluate the theory. Results for bothtest cases indicated that the theory fitted observational data well within acceptable limits.

[发布机构] Stellenbosch University