Passive Tracking and Information Theory

Estimation of kinematic attributes using passive sensors is a key problem in air and missile defense as well as anti-submarine warfare and airborne surveillance. Traditional deterministic observability criteria are based on engagement and observation kinematics, and imply infinite tracking times and noise-free measurements. Real systems have noise corrupted measurements and finite tracking times or finite numbers of measurements. These "real world " constraints may be accommodated using information-theoretic concepts. Thus criteria may be formulated to ensure the necessary and sufficient conditions for unique estimates. These criteria are based on metrics which take into account noisy and finite numbers of measurements, and provide a basis for a definition of "stochastic observability". The intent of this paper is to introduce the deterministic criteria, develop a modification using information-theoretic distance measures to form a stochastic observability criteria, and finally to illustrate this development via simple examples. 1