Nonlinear effects in the correlation of tracks and covariance propagation

When the Air Force Space Surveillance Network observes an object that does not correlate to an entry in the Space Object Catalog, it is called an Uncorrelated Track (UCT). Some of these UCTs arise from objects that are not in the Space Catalog. Before a new object can be added to the catalog, three or four UCTs must be associated so that a meaningful state can be estimated. Covariance matrices can be used to associate the UCTs in a more statistically valid and automated manner than the current labor-intensive process, however the choice of parameters used to represent the orbit state have a large impact on the results. Covariance-based track association was performed in 10-day simulations of 1000 space objects within a 20-km band of semimajor axis using many different orbit parameters and propagation methods and compared to a fixed position gate association method. It was found that Cartesian covariance with linearized propagation performed poorly, but when propagated with the Unscented Transform the results were much better. Elliptical curvilinear coordinates also performed well, as did covariance in osculating equinoctial elements propagated with the Unscented Transform, but a covariance in mean equinoctial elements propagated with the Unscented Transform achieved the best results. 2010 International Astronautical Federation. All rights reserved.

Nonlinear effects in the correlation of tracks and covariance propagation Conference Paper