CAPE CANAVERAL, Fla. (AP) — As more and more space junk comes crashing down, a new study shows how earthquake monitors can better track incoming objects by tracking their sonic booms.
Scientists reported Thursday that seismic readings from sonic booms that were generated when a discarded module from a Chinese crew capsule re-entered Southern California in 2024 allowed them to place the object’s path nearly 20 miles (30 kilometers) farther south than predicted by radar from orbit.
Using this method to track uncontrolled objects falling at supersonic speeds, they said, could help recovery teams reach any surviving pieces more quickly – crucial if the debris is dangerous.
“The problem right now is that we can track things very well in space,” said Benjamin Fernando of Johns Hopkins University, the lead researcher. “But once you get to the point where you’re actually breaking up in the atmosphere, it becomes very difficult to track.”
His team’s findings, published in the journal Science, focus on just one debris event. But researchers have already used publicly available data from seismic networks to track a few dozen other re-entries, including debris from three SpaceX Starship test flights in Texas.
A growing concern among scientists and others is that falling space debris could hit an aircraft in flight.
“There are thousands, tens of thousands, more satellites in orbit than there were 10 years ago,” including SpaceX’s Starlinks and other companies’ internet satellites, Fernando said. “Unfortunately, we don’t have anything other than the company’s word that when they break up, they burn up completely in the atmosphere.”
Fernando, who usually studies earthquakes on the moon and Mars, joined Constantinos Charalambous of Imperial College London the day after the Chinese debris scattered across the California sky in 2024. Over time, they collected data from more than 120 seismometers that picked up the sonic booms from the reentry, using that data to suspect the object’s path.
China’s uncontrolled module had been abandoned in a decaying orbit since it was cut off from the Shenzhou-15 capsule that returned three Chinese astronauts from their home space station in 2023. booms. In addition to trying to trace the fall of the object, the seismic readings provided a sense of the cascading wreckage, Fernando said.
Fernando acknowledged that it is impossible to know how close his team’s predictions are to the actual path since no debris on the ground has been reported.
The aim is to ascertain, in a few minutes or even seconds, the speed and direction of the incoming space junk as well as its fragmentation. In remote areas such as the South Pacific, nuclear explosion monitoring stations could potentially track sonic booms to fine-tune descent paths. That’s where NASA plans to lift the International Space Station in five years. SpaceX is working on the deorbiting vehicle to ensure a controlled entry.
Fernando is looking to eventually publish a catalog of seismically tracked incoming space objects, while improving future calculations by considering the effect of wind on falling debris.
In an accompanying article in Science, Chris Carr of the Los Alamos National Laboratory, who was not involved in the study, said that more research is needed to reduce the time between the final plunge of an object and the determination of its course.
For now, Carr said this new method “unlocks the rapid identification of debris fall zones, which is key information as Earth’s orbit is expected to become increasingly crowded with satellites, leading to an increased influx of space debris.”
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