  A procedure for the design of fixed-gain tracking filters, using an
augmented-state observer with signal and interference subspaces, is proposed.
The signal subspace incorporates an integrating Newtonian model and a
second-order maneuver model that is matched to a sustained constant-g turn; the
deterministic interference model creates a Nyquist null for smoother track
estimates. The selected models provide a simple means of shaping and analyzing
the (transient and steady-state) response of tracking-filters of elevated
order.
