Infrasonic analysis of the October 28, 2014 Antares rocket failure at Wallops Island, Virginia, using video recordings as ground truth

We used close-in video recordings of the October 28, 2014 Antares rocket failure at Wallops Island, VA to establish an event timeline to aid in the analysis of infrasound recordings made at nearby stations of the IRIS Transportable Array. Our timeline is ignition at 22:22:38 UTC, liftoff at + 4 s, bright plume and first explosion at an altitude of 300 m at + 15 s, second large explosion as the rocket hits the ground at + 25 s, followed by the excess fuel burn lasting some 400 s. Both explosions and the fuel burning events are seen in the infrasound data recorded at IRIS station S61A at a distance of 23 km, and the two explosions can be seen out to distances of 130 km. High resolution time frequency analyses of the infrasound signals at the distant stations show a dispersed signal from 0.5–8 Hz with a peak at 1.7 Hz and corresponding group velocity of 360 m/s. This dispersion curve corresponds to a low velocity duct at the surface with a thickness of approximately 1.2 km. The relatively fast group velocity can be attributed to the prevailing winds. Explosion yield estimates using the BOOM model indicate equivalent TNT yields of 20 and 200 tons for the two explosions. Co-located seismic and infrasound sensors at two stations allow us to estimate the acoustic-to-seismic spectral ratio at 1–10 μm/s/Pa. However, low coherence between the acoustic and seismic signals implies a non-linear transfer function at the sites.