Search

Intentional or unintentional spiraling maneuvers on the part of a tactical ballistic missile target can make it particularly difficult for a pursuing missile to hit. The paper first reviews why it is difficult to hit a spiraling target with proportional navigation guidance. It is then shown that by using a special purpose linear Kalman filter that is specifically tuned for a spiral maneuver in conjunction with an advanced guidance law it is possible to dramatically improve system performance over that of a proportional navigation guidance system. However, in order for the necessary filtering and guidance to work properly the targets spiraling frequency must be known. If the spiraling frequency is unknown other methods must be used. The paper investigates two schemes for deriving the spiraling frequency of the target. The first scheme involves using a bank of Kalman filters, each of which is tuned to a different spiraling frequency. Various schemes for identifying which filter in the filter bank is tuned to the actual target frequency are investigated. The second method for deriving the target frequency involves using a single extended Kalman filter that explicitly estimates the target spiraling frequency. It is shown that such an extended Kalman filter when used in conjunction with an advanced guidance law can dramatically improve system performance., Prepared in collaboration with The Charles Stark Draper Laboratory, Inc., Cambridge, MA.