Flight parameter estimation using time delay and intersensor multipath delay measurements from a small aperture acoustic array.

A ground-based acoustic sensor array can be used to estimate the complete set of flight parameters of a jet aircraft or other airborne source of broadband sound in transit by measuring the differential time of arrival (DTOA), or the time delay, of the direct path signal at each sensor pair of the array over a sufficiently long period of time. This paper studies the possibility of using intersensor multipath delay measurements to improve the precision of the flight parameter estimates for a small aperture array, without increasing the array's intersensor spacing or the observation time for more time delay measurements. Intersensor multipath delay is defined as the DTOA of the direct path signal at one sensor and the ground-reflected path signal at another sensor. The flight parameter estimation algorithm is formulated and a simplified Cramer-Rao lower bound error analysis is presented, which shows that the standard deviations in the flight parameter estimates are greatly reduced when intersensor multipath delay measurements are used together with time delay measurements. The effectiveness of the proposed flight parameter estimation method for small aperture arrays is verified using both simulated and real data.