Characterizing the 2022 South Atlantic fireball using infrasound recordings of the International Monitoring System

On 7 February 2022, around 20:00 UTC, a large meteoroid entered the Earths atmosphere around 500 km off the coast of Namibia and South Africa. NASAs Center for Near Earth Object Studies (CNEOS) lists the event as a fireball with an impact energy of 7 kt of TNT equivalent. This energy estimate is about 60 times lower than for the 2013 Chelyabinsk fireball (440 kt, CNEOS), which was broadly covered in the media. Infrasound measurements can be an independent information source for fireball events. Their infrasonic signatures originate from either the hypersonic trajectory, which emits ablational waves, or the explosive fragmentation, which emits a ballistic shock wave. Relations such as ReVelles law can even be used for energy release estimates based on infrasound detection parameters such as the dominant period of the signal. The analysis of infrasound data from the International Monitoring System (IMS) for the Comprehensive Nuclear-Test-Ban Treaty (CTBT) revealed that the Chelyabinsk fireball was the strongest event ever recorded by the IMS infrasound network at that time, when 20 out of 42 existing stations detected it. The second-strongest event of this type in the IMS era was the Bering Sea bolide that occurred on 18 December 2018 (49 kt, CNEOS), with a comparable portion of infrasound stations detecting it (25 out of 51, according to Pilger et al. 2019, doi: 10.3390/atmos11010083). For the 2022 South Atlantic fireball, we have found signatures at 20 infrasound stations of the IMS, too, out of 53 stations certified nowadays. We further characterize the event using the infrasound observations, model the infrasound propagation between the elevated source and the arrays, and assess the detection capability to explain the large number of detecting stations. We also use the IMS data for estimating an energy release, and revisit previous strong events such as Chelyabinsk using state-of-the-art array processing methods and enhanced configurations. These comprise the Multi-Channel Maximum-Likelihood (MCML) method or the one-third-octave band configuration within the Progressive Multi-Channel Correlation (PMCC) method, respectively.