Active Removal and Situational Awareness of Space Debris in Low Earth Orbits

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The build-up of debris from human activities in space over the past 60 years has become a critical issue, particularly in the very commercial low Earth orbits (LEO). It is widely accepted that this situation must be addressed if humans are to continue sustainable exploitation of near Earth space. This acknowledgement has spurred intense research on ways to curtail space debris growth, and remediate the space environment. I propose to increase technology readiness levels of existing solutions, to advance our understanding and to develop novel methodologies to address key issues in this multifaceted problem. The first focus of this proposal is on active debris removal. There is now broad consensus on the need to remove five to ten large debris objects per year; yet, there is no agreement on the best technology to deploy for such a mission. Building on my prior research on the use of tethered nets for capture of large space debris, I will further advance the tethered-net solution through the development and evaluation of net closing methods to ensure debris containment; by investigating strategies for system stabilization after capture; and through experimental demonstration of the tethered-net concept for debris capture. For the subsequent phase of the mission, the de-orbiting of the resulting tethered chaser-debris system, I propose to investigate tether-assisted concepts---through tether swinging and spinning---for braking the debris into a descent towards the Earth's atmosphere. My second research focus falls under the umbrella of space situational awareness of the debris environment. Within this broad domain, I will work on improving our understanding and advancing prediction capabilities for the motion of large space debris, with emphasis on their rotational motion. This research will answer the basic questions: where will the debris be at some time in the future and how will it be spinning? Because the debris are tumbling uncontrollably, their attitude has a time-varying effect on the perturbation forces and torques experienced in orbit, such as, the aerodynamic drag and solar radiation pressure. These in turn directly influence the orbit and location of debris. We will work to expand our understanding of how uncertainties in our current models of perturbation effects affect the uncertainties in the propagation and formulate stochastic models to quantify these effects. We will explore the use of observational data, jointly with our predictive models, to formulate estimation algorithms for parameters, perturbations and the attitude motion of the debris. Canada is a space faring nation: it launches satellites and Canadian people depend on our space assets to function reliably over their life-time. Given the threats presented by space debris to functional assets, it is critical that we have expertise to participate in future debris removal missions, as well as, the knowledge and tools to predict the impact of debris on the space environment.