Tracking and intercepting spiraling ballistic missiles

Intentional or unintentional spiraling manoeuvres on the part of a tactical ballistic missile target can make it particularly difficult for a pursuing missile to hit. The paper first presents normalized miss distance curves showing how the target spiraling frequency and amplitude along with the interceptor guidance system time constant determine the miss distance for a proportional navigation guidance system. It is then shown how more advanced guidance techniques can be used to improve the system performance against spiraling targets. The advanced guidance techniques require knowledge of various target states plus the target weave frequency. Various Kalman filtering options for estimating the states required for the advanced guidance law are presented. Preliminary miss distance results are presented with each of the candidate filtering options.