Earthquake Sensors Offer New Way To Track Falling Space Junk

As Earth’s orbit becomes increasingly crowded with satellites, scientists are developing new tools to manage the growing risk from falling space debris. A recent study shows that earthquake monitoring systems can be repurposed to track uncontrolled objects reentering Earth’s atmosphere by detecting the sonic booms they generate, potentially improving safety and debris recovery efforts.

Seismic Signals Reveal Reentry Paths

Researchers found that seismic readings captured during the 2024 reentry of a discarded module from China’s Shenzhou-15 crew capsule over Southern California provided crucial insights. By analysing sonic booms recorded by more than 120 seismometers, scientists were able to reconstruct the object’s trajectory. The results placed the debris path nearly 30 kilometres south of where radar-based orbital predictions had indicated, highlighting limitations in current tracking once objects begin breaking up in the atmosphere.

Limits of Conventional Space Tracking

Objects in orbit are tracked with high precision, but once they descend at supersonic speeds and fragment, monitoring becomes far more difficult. According to lead researcher Benjamin Fernando of Johns Hopkins University, this gap poses challenges for hazard assessment and recovery, especially if debris contains hazardous materials. Seismic networks offer a ground-based method to bridge this critical final phase of tracking.

Rising Risks From Satellite Crowding

The concern is growing as the number of satellites has multiplied over the past decade. Large constellations such as SpaceX’s Starlink network and similar projects have dramatically increased orbital traffic. Scientists warn that assurances of complete atmospheric burn-up often rely on company claims, while the risk of debris striking aircraft or populated areas cannot be fully dismissed.

Important Facts for Exams

• Uncontrolled space debris can generate sonic booms during atmospheric reentry.
• Seismometers can detect pressure waves from supersonic objects.
• Satellite numbers in low Earth orbit have increased sharply in the last decade.
• Tracking reentry paths is critical for aviation safety and debris recovery.

Future Applications and Global Monitoring

Beyond the Chinese module, researchers have already applied this method to track several other reentries, including debris from failed SpaceX Starship test flights. In remote regions such as the South Pacific, seismic and nuclear-test monitoring stations could further refine descent predictions. The technique may prove valuable as agencies like NASA plan complex operations, including the controlled deorbiting of the International Space Station later this decade. Scientists are now working towards faster calculations and a global catalogue of seismically tracked reentries, aiming to respond within minutes as space junk continues to fall back to Earth.