Tracking of Spiraling Reentry Vehicles with Varying Frequency using the Unscented Kalman Filter
Ernest J. Ohlmeyer, Padmanabhan K. Menon, Jinwhan Kim · 2010
As ballistic targets reenter the earth’s atmosphere, they undergo rapid deceleration and may perform spiraling motion that can make accurate tracking very difficult. A variety of filter structures have been proposed for this problem, including variants of the Kalman filter. The present work employs a new target dynamics model combined with an Unscented Kalman Filter (UKF) to yield an effective tracking solution. The paper considers the case of both constant and time varying spiral frequency. The new target model includes, in addition to position and velocity states, a modified drag coefficient (inverse ballistic coefficient), the target spiral frequency, and two harmonic states describing the periodic rotation of the target body around its velocity vector. The UKF with new target model produced very accurate tracking for the case of constant frequency. When the frequency varied with time, the new algorithm still achieved very satisfactory performance in tracking the changing target states. For the latter case, the sensitivity to angle measurement accuracy using a reduced set of measurements was also evaluated.