Seismoacoustic analysis of a Falcon-9 rocket stage reentry on 19 February 2025

Since more than sixty years, rockets have transported tens of thousands of satellites to space. More and more rocket stages and other space debris are returning to Earth, sometimes intentionally, sometimes unexpected.  Such descending objects move supersonically through the atmosphere, disintegrate, and can even explode. During these processes, they can produce shock and sound waves which can be monitored using pressure sensors at the Earth’s surface. The infrasound component of the International Monitoring System (IMS) for monitoring compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT), as well as additional national infrasound arrays, are therefore well suited for detecting and characterizing such events. Additionally, the infrasound waves can couple to the subsurface as seismic waves.

On 19 February 2025, the upper stage of a SpaceX Falcon 9 rocket reentered Earth’s atmosphere approximately over Ireland and produced a bright fireball along its trajectory over the United Kingdom, the Netherlands, northern Germany and western Poland, where fragments of the rocket were eventually recovered. This highlight case of a reentry of space material was not only visually observed, but also recorded by various scientific instruments, including infrasound arrays in the Netherlands, Germany, Sweden and Norway and the dense seismic borehole network in the northern part of the Netherlands. This case study investigates the potential of infrasound to monitor space rockets during their reentry. We characterize the Falcon 9 reentry event and reconstruct its trajectory based on infrasound and seismoacoustic recordings.