Kyle Alfriend, Texas A&M University, Inkwan Park, Texas A&M University
Keywords: Orbit state uncertainty, space situational awareness, conjunction assessment.
Abstract:
The orbit state covariance is used in the conjunction assessment/probability of collision calculation. It can also be a valuable tool in track association, maneuver detection and sensor tasking. These uses all assume that the uncertainty is Gaussian. Studies have shown that the uncertainty at epoch (time of last observation) is reasonably Gaussian, but the neglected nonlinearities in the covariance propagation eventually result in the uncertainty becoming non-Gaussian. Numerical studies have shown that for space objects in low Earth orbit the covariance remains Gaussian the longest in orbital element space. It has been shown that the covariance remains Gaussian for up to 10 days in orbital element space, but becomes non-Gaussian after 2-3 days in Cartesian coordinates for a typical LEO orbit. The fundamental question is when does it become non-Gaussian and how can one given the orbit state and covariance at epoch determine when it occurs. A tool that an operator could use to compute the approximate time when the when the uncertainty becomes non-Gaussian would be useful This paper addresses the development of such a tool.
Date of Conference: September 20-23, 2016
Track: Astrodynamics