Real-Time Drag Determination for Kwajalein Missile Range (KMR) Tracking Development

Although the wideband, narrow beam radars at KMR are capable of tracking well-behaved targets during reentry, the radars do not reliably maintain track on targets whose drag profiles deviate significantly from a priori predictions. The objective of this effort is to determine the feasibility of augmenting existing tracking filters for the KMR radars to allow real-time computation, correction, ad prediction of reentry drag experienced by objects in track. The existing KMR track filters attempt to compensate for drag excursions by increasing the process noise when predictions are observed to deviate from the measurements. Rather than simply increase the process noise, our proposed approach is to use the observed deviations between the predicted and observed measurements to modify/improve on our a priori estimate of vehicle drag profile. Our approach can be described as one of using drag as an additional state variable which is estimated in real time using the predictor/corrector processes of Kalman filtering. A digital simulation will be used to refine our new algorithm and to compare its performance with the existing KMR track filters for a wide spectrum of drag profiles. Feasibility of the revised tracker will be evaluated in terms of its ease of implementation in the existing rel-time programs of the KMR radars, and the ability of the existing computing hardware to absorb the additional computational load.