Refraction corrections to source localization using an acoustic array suspended below an aerostat

Abstract

Acoustic sensor arrays suspended below tethered aerostats have several advantages in detection and localization of sources on the ground in comparison with ground-based sensors. Aerostats can be elevated up to 1-2 Km above the ground where the temperature and wind velocity can significantly differ from their values close to the ground. Therefore, due to refraction, a ray trajectory that connects a source on the ground and an aerostat can bend significantly resulting in different directions of sound propagation along this trajectory. However, so far, refraction has been ignored in source localization using aerostats. In this paper, a theory is developed that allows one to find the source coordinates more accurately by taking into account refraction of sound signals emitted by the source. The source coordinates are expressed in terms of direction of sound signal propagation near the aerostat, the coordinates, and orientation of the aerostat, and the vertical profiles of temperature and wind velocity. Other meteorological parameters may also be incorporated, if available, such as time-of-day, geographical features, and historical weather trends.