Development of a Nonlinear Probability of Collision Tool for the Earth Observing System

The Earth Observing System began routine conjunction threat assessment of its member missions starting in 2004. It was quickly determined that a capability was needed to analyze conjunctions having nonlinear relative motion. An algorithm was developed that reduces the complex nonlinear relative motion into small linear segments that are easy to evaluate. The algorithm shows good agreement to the existing linear theory when used to analyze linear relative trajectories and for simple nonlinear cases for which solutions are known. The algorithm has been implemented in a software tool that accurately propagates the spacecraft states and covariances. The resulting 3D Collision Probability Tool is now being used by EOS analysts to study conjunction events.