Semi-Adaptive Numerical Filters for Use in Best Estimate of Trajectory Computations

When more than one radar is being used to track a re-entry vehicle during its re-entry phase, a Best Estimate of Trajectory (BET) computation is used to find the vehicle´s position. In addition, two ancilliary numerical filters may be used, one to integrate radar range rate measurements so that they may be inputted to the BET in an efficient manner, and the other to differentiate the BET output so as to obtain the vehicle´s velocity and acceleration. The ancilliary filters are discussed in this paper, and it is shown how to design them so that they adapt their characteristics to the a priori statistics of the actual data being handled.