Recent work in deploying infrasound (low frequency sound) sensors on aerostats and free flying balloons has shown them to be viable alternatives to ground stations. However, no study to date has compared the performance of surface and free floating infrasound microbarometers with respect to acoustic events at regional (100s of kilometers) range. The prospect of enhanced detection of aerial explosions at similar ranges, such as those from bolides, has not been investigated either. We examined infrasound signals from three 1 ton TNT equivalent explosions using microbarometers on two separate balloons at ranges of 280 to 400 km and ground stations at ranges of 6.3 to 350 km. Signal celerities were consistent with acoustic waves traveling in the stratospheric duct. However, significant differences were noted between the observed arrival patterns and those predicted by an acoustic propagation model. Very low background noise levels on the balloons were consistent with previous studies that suggest wind interference is minimal on freely drifting sensors. Simulated propagation patterns and observed noise levels also confirm that balloon-borne microbarometers should be very effective at detecting explosions in the middle and upper atmosphere as well as those on the surface.

Download the data file, unzip it, and then run the following shell commands to concatenate and then uncompress the files:

cat usie.tgz.* | tar xzv