Pursuer Aim Identification for an Aircraft Formation Using a Passive Sensor Without State Estimation

In a pursuit evasion scenario, a missile (pursuer) launched from the ground or the air aims to intercept an aircraft (evader) flying in formation. This article considers the problem of whether an aircraft is aimed by a missile or not, based only on the line-of-sight (LOS) measurements from an on-board passive sensor. The motion of the missile is assumed to be governed by pure proportional navigation guidance. Previous works on this problem estimate the missile's state motion parameters, which, for a passive sensor, requires a numerical search, i.e., significant computation time, algorithm complexity and is ill-conditioned. We present a methodology that relies on the geometric relationship between the aircraft and the missile without state estimation. A plane is defined by the aircraft velocity vector and one aircraft-to-missile LOS vector, and if a second LOS vector at a subsequent time is in this plane, it is known that the missile aims at the aircraft. A coplanarity test is designed on the basis of these three vectors. We then provide a test statistic for inferring whether the airplane is aimed by the missile. An approximate distribution is used to set the threshold for detection and false alarm probabilities. Simulation results are presented for surface-to-air and air-to-air missile scenarios to illustrate the efficiency of the proposed method and compared to the state estimation method.