Accession Number : ADP003794

Title :   Long Range Acoustic Tracking of Low Flying Aircraft,

Corporate Author : MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB

Personal Author(s) : Landers,T. E. ; Lacoss,R. T.

Report Date : DEC 1978

Pagination or Media Count : 10

Abstract : Data from a 5 meter array of microphones has been collected and analyzed in the band 20-200 Hz to find the accuracy to which the azimuth of low-flying subsonic aircraft can be tracked and to measure signal levels as a function of range. Flight paths were radar tracked and recorded on digital tape. Propagation characteristics were calculated from measured meteorological data and were used to help interpret observed signal level variations. The aircraft included helicopter, prop-driven and jet aircraft which flew 30 km reversed linear tracks at altitudes of 70 m, 300 m and 1 km. Azimuth was measured by applying maximum-likelihood frequency-wavenumber analysis to the digitized data from the fractional wavelength array of microphones. Measured azimuths, after the appropriate moving source corrections, were found to be accurate to within a few degrees at ranges well beyond 5 km. Filtering and array gain allowed us to obtain good azimuth estimates for aircraft signals at least 10 dB below the background noise level. (Author)

Descriptors :   *Acoustic tracking, *Aircraft detection, Low altitude, Subsonic flight, Azimuth, Flight paths

Distribution Statement : APPROVED FOR PUBLIC RELEASE