Flight Parameter Estimation Using Instantaneous Frequency Measurements From a Wide Aperture Hydrophone Array

In this paper, a narrowband method based on the acoustical Doppler effect is proposed for estimating the full set of five flight parameters, along with the propeller blade rate, of a turboprop aircraft as it transits over a wide aperture hydrophone array in a straight line at constant speed and constant altitude. The five flight parameters describe fully the linear trajectory of the aircraft's transit. The basic principle of the proposed method is to measure the temporal variation of the instantaneous frequency (IF) of the acoustic signal received by each sensor of the array and then to minimize the sum of the squared deviations of the IF estimates from their predicted values over a sufficiently long period of time for all sensors. The minimization is performed numerically subject to a set of constraints on the source parameters to be estimated. The IF model for the received signal at each sensor of the array and the initial parameter estimates required for the numerical minimization are derived. The effectiveness of the proposed method is demonstrated using both simulated and real data.