Seismoacoustic Analysis of a Falcon 9 Rocket Stage Re-Entry Over Central Europe on 19 February 2025

Abstract On 19 February 2025, a SpaceX Falcon 9 rocket stage re-entered the atmosphere over Ireland’s west coast. It produced a sustained fireball along its trajectory across the United Kingdom, the Netherlands, northern Germany, and western Poland. Seismic and infrasound stations in the Netherlands and Germany, as well as infrasound arrays in Sweden and Norway, recorded the event. We characterise the re-entry as a line source and reproduce the trajectory using the seismoacoustic observations of more than 80 stations. The majority of the stations detected two distinct signal arrivals. We investigate the detection pattern with varying time intervals between these signals across the station networks, benefiting from both a dense seismic borehole network in the Netherlands and co-located measurements of infrasound and seismic stations. Acoustic arrivals at stations up to 150 km distance from the trajectory originate from the shock wave of the Mach cone due to the hypersonic velocity of the re-entering debris. Infrasound arrays at distances between 400 and 900 km additionally recorded signals that also reflect the west-to-east movement of the source. Allsky7 camera observations and infrasound propagation simulations utilising the UA-ICON model atmospheric representation enable the validation of the seismoacoustic characterisation of the re-entry. Co-located atmospheric lidar measurements provide valuable insight into small-scale atmospheric dynamics influencing infrasound propagation conditions. This study demonstrates that dense seismoacoustic station networks, including infrasound arrays, can provide valuable ground-based and time-constrained evidence of re-entering space debris over a wide horizontal extent. In an era of an increasing number of rocket launches and deorbiting space debris, these seismoacoustic observations can also be relevant for space agencies to re-analyse such events.