AN OPTIMAL METHOD FOR ESTIMATING THE REEN TRY TRAJECTORY OF A BALLISTIC VEHICLE WITH LONGITUDINAL ACCELERATION MEASUREMENTS

This paper deals with a new method for estimating the trajectory of a hypervelocity vehicle in reentry, by means of longitudinal acceleratio n measurements. In the context of an exponential atmosphere, we assume that the relationship between the air density and the altitude is kno wn. We prove that, during the deceleration phase, these measurements a re sufficient to determine the initial state of the body, namely the p ath inclination, the velocity and the altitude. We analyze the accurac y achieved with such measurements by computing the Cramer-Rao lower bo und. We present a fast maximum likelihood estimator and a Kalman filte r. Simulations confirme the good performance of these methods, already predicted by the theory.