Infrasound as a tool for detection and characterization of bolides

Very bright meteors, also known as fireballs and bolides, are produced when extraterrestrial objects larger than approximately 10 cm in diameter enter dense regions of the Earths atmosphere. Besides the luminous phenomenon, bolides also generate shock waves, which decay to low frequency acoustic waves or infrasound. Depending on initial conditions, atmospheric propagation paths, and the mode of shock production, infrasound emanating from a bolide can be detected by microbarometers hundreds and even thousands of kilometers away. Unlike other sensing modalities that might have geographic (e.g., inaccessible regions), time-of-day (e.g., optical) or other limitations, infrasound can be utilized continuously (day and night) on a global scale. Hence, infrasound can be leveraged towards detection and localization of bolides, as well as estimating their explosive yield. Bolide infrasound detections date back to the early 20th century. On June 30, 1908, an extraterrestrial object exploded over Tunguska, Siberia, generating low frequency acoustic waves that mark the first known instrumentally observed bolide infrasound. During the mid-20th century, ten large bolides were detected by infrasound stations meant for explosion monitoring. Since the mid-1990s, many more events have been detected via infrasound. However, characterization of bolides through infrasound is not without its challenges, mainly because no two bolide events are alike. Systematic studies and data fusion can be leveraged towards efforts to better constrain some key parameters. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.