Space debris detection could use seismic networks to track reentering fragments

Johns Hopkins researchers used seismograph records to trace the breakup of China’s Shenzhou-15 module over Southern California in April 2024, and published their results in Science on Jan. 22. They report that seismic networks can record shockwaves from reentering debris and may help locate where fragments fall.

Researchers at Johns Hopkins demonstrated that existing networks of seismometers can detect shockwaves from objects reentering the atmosphere. They analyzed historic seismograph records to track the breakup of a 1.7-ton Chinese Shenzhou-15 orbital module over Southern California in April 2024. The seismic-derived track and calculations matched eyewitness videos of the fiery breakup. The team published the work in the journal Science on January 22 and said the method could help verify where fragments entered the atmosphere and whether any reached the ground. Key findings: - Seismic sensors recorded shockwaves or sonic booms from the Shenzhou-15 reentry, allowing reconstruction of speed, trajectory, descent angle and fragmentation pattern. - The Shenzhou-15 module had been falling while passing over major population centers on six continents and broke up over Southern California in April 2024. - The seismic analysis matched multiple eyewitness videos and was published in Science on Jan. 22. - Radar tracking can be limited because vaporizing fragments create plasma that interferes with radio signals. - Networks of seismometers already exist worldwide and have recorded aircraft sonic booms and other acoustic signals; detecting reentries would rely on software rather than new hardware. - NASA estimates about 10,000 tons of old spacecraft and debris orbit Earth, and scientists estimate roughly 49 tons of meteorites enter the atmosphere daily, with 10–15 reaching the surface. Summary: The study shows that seismometer networks can provide observable tracks of unexpected reentries as Earth’s orbit becomes more crowded, and researchers said those tracks could help locate hazardous fragments and narrow searches for meteorites. The team hopes to develop software to passively monitor seismic records for similar sonic-boom signatures. Further development and broader testing were not detailed.