On the usage of derived quantities in tracking: Energy and other estimators

Typically, the tracking and estimation community has been concerned with the direct problem of tracking a threat in a near optimal fashion. The usage of secondary quantities or derived quantities from state estimates that can be used for other purposes than tracking have been ignored. An example of a derived quantity that is useful directly for tracking and classification is the energy associated with the threat. We discuss a number of such informative priors that can be useful to pure tracking applications as well as how dissipation of energy and ballistic coefficients can be estimated indirectly.