Projects on Space Situational Awareness - Tracking of Space Debris, Collision Avoidance and Removal of Space Debris

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The number of natural and man-made objects (space debris) around the Earth is growing rapidly, thereby posing a serious risk of collision with operational satellites. Hence it has become necessary for all satellite operators to possess tools that will provide them capability to determine and predict physical location of these objects with sufficient accuracy, predict collision probability, and devise schemes to carry out collision avoidance maneuvers in an optimal manner. At the same time, methods to remove space debris, both passive and active, must also be developed. The objective of the proposed research program is to make advances in the satellite dynamics area dealing with the above-mentioned issues. Specifically, the following studies will be conducted: (i) Coupled orbit-attitude propagation of space debris will be studied. Appropriate mathematical models will be developed considering various environmental and perturbation effects. Efficient computational tools will be developed to analyze the models by exploiting the fact that the propagation involves multiple time scales. (ii) Details of several active and passive debris removal methods will be investigated: (a) The debris must be transferred to a graveyard orbit after its capture. An obvious method is to tow the debris to the graveyard orbit using a tug and a tether. Various aspects of this towing problem will be studied, including how to carry out a low-thrust orbital transfer of a tethered system optimally. (b) One passive debris removal method, that has a lot of potential, involves attaching an electrodynamic tether to the debris to make the orbital decay faster. Many dynamics and stability issues associated with these systems are not well-understood at present. These will be investigated. (c) A tethered space manipulator can have some advantages for capturing space debris. Dynamics and control of these tethered manipulators will be studied. (iii) Space assets conduct collision avoidance maneuvers regularly to avoid space debris heading towards them. The maneuvers involve many decisions: how many impulses, when to initiate the maneuver, when to return to the original orbit, what is the miss distance, etc. The goal of this project is to evaluate the consequences of these decisions and devise optimal ones. One of the key outcomes of the research program is to train highly qualified personnel in the area of space technology. It is estimated that 1 postdoctoral fellow, 6 doctoral students, 6 Master's students, and several undergraduate students will work with me on various sub-projects associated with the research program over the 5- year period. The research program will not only advance knowledge in the area of space debris research, but also will benefit Canadian space industry and satellite operators. It also has the potential to contribute to the space situational awareness activities of the Department of National Defence of Canada.