Thermospheric densities derived from spacecraft orbits: Accurate processing of two-line element sets

Impact of Solar Forcing on Thermospheric Densities and Spacecraft Orbits from CHAMP and GRACE

KAM torus frequency generation from two line element sets

The Kolmogorov Arnold and Moser (KAM) theorem states that a lightly perturbed Hamiltonian system will have solutions which lie on a torus. Earlier work by the second author has shown that most Earth satellite orbits perturbed by the geopotential lie on KAM tori. The problem then arises as to how to convert the current satellite tracking orbits to KAM tori. A KAM torus is characterized by three ...

Thermospheric global average density trends, 1967–2007, derived from orbits of 5000 near-Earth objects

[1] We use orbit data on 5000 near-Earth space objects to investigate long-term trends in thermospheric total mass density, which has been predicted to decrease with time due to increasing CO2 concentrations. We refine and extend to 2007 previous density trend estimates, and investigate solar cycle-dependent bias in empirical density models previously used to filter out solar irradiance effects...

Fuzzy Sliding Mode for Spacecraft Formation Control in Eccentric Orbits

The problem of relative motion control for spacecraft formation flying in eccentric orbits is considered in this paper. Due to the presence of nonlinear dynamics and external disturbances, a robust fuzzy sliding mode controller is developed. The slopes of sliding surfaces of the conventional sliding mode controller are tuned according to error states using a fuzzy logic and reach the pre-define...

Improved forecasting of thermospheric densities using multi-model ensembles

This paper presents the first known application of multi-model ensembles to the forecasting of the thermosphere. A multi-model ensemble (MME) is a method for combining different, independent models. The main advantage of using an MME is to reduce the effect of model errors and bias, since it is expected that the model errors will, at least partly, cancel. The MME, with its reduced uncertainties...