<title>Multiple-model filters for boost-to-coast transition of theater ballistic missiles</title>

Abstract

The uncertainty in the time of ballistic missile transition from boost to coast phase poses significant problems to tracking sensors. The Interacting Multiple-Model (IMM) filter monitors this transition through the application of two Kalman filters, whose inputs and outputs are weighted by computed probabilities that the missile is in boost or coast phase. The ability of IMM to produce accurate tracks early in the midcourse phase is compared with that for simpler models that use a 'nearest neighbor' approach to determine the best fit to sensor measurements. Track output -- state vectors and error covariance matrices -- are handed off in the post-boost phase to midcourse sensors, which propagate tacks using either centralized measurement fusion or tracklets; that is, tracks computed so that their errors are not cross-correlated with those from other tracks of the same target.