The combustion of fossil fuels is currently used to meet the majority of global energy needs. Given the anticipated future shortages of fossil fuels, and their contribution to greenhouse gas production and global warming, sustainable methods for energy production will need to be further developed. In this paper, we extend our results presented in the 2011 AIAA Atmospheric Flight Mechanics Conference to a full study of the observability properties of a 3D ground tether energy (GTE) system. Will will first review the dynamical and controllability properties of the GTE system from our previous work. We will then present the observability properties for the GTE system given a certain set of realistic system parameters. We restrict ourselves to the case where we only measure tether length and tether and kite orientation variables, with no sensing of any velocity variables. This study helps understand which type of sensors are needed if we are to be able to completely determine the state of the system using any of the available state estimation techniques. The GTE system was found to be observable if at least the tether crosswind orientation angle and either the tether length or the tether downstream orientation angle are measured, though such a sensing scenario might result in a very weakly observable system.
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