Helicopter tracking using acoustic arrays

Tracking of airborne vehicles using distributed acoustic arrays is considered here. Three tetrahedral acoustic arrays are distributed over roughly 1.5 sq. miles area to track a helicopter. The bearing angles are estimated at the significant harmonics of the fundamental frequency of the helicopter rotor using multiple signal classification (MUSIC). Some of the issues using the bearing estimates at lower harmonics are discussed. The altitude of the helicopter is estimated by fusing the covariances from all three arrays and performing MUSIC on them. An extended Kalman filter is used to track the helicopter and the tracking results are presented.