In recent years, the number of unused space artifacts re-entering the atmosphere has grown exponentially, which can pose a risk.
Now, a scientific team presents a novel way to track them as they fall, almost “in real time” and using ground-based seismic sensors, a technique that makes it possible to capture the sonic booms generated during re-entry at supersonic speeds.
Seismic sensors track space junk in California
Using information from devices located in southern California and Nevada to detect the sonic booms of re-entering debris, the methodology was tested with open source data from the orbital module of the Chinese spacecraft Shenzhou-15, obtaining a location significantly south of the predicted trajectory.
According to the study, the actual trajectory was located about 30 kilometers further south than what radar systems from orbit had estimated.
The results are published in the journal Science, in an article signed by Benjamin Fernando, from Johns Hopkins University (United States), and Constantinos Charalambous, from Imperial College London. Although the study focuses on a single event, the authors note that they have already used public seismic networks to track several dozen additional reentries.
Risks of space debris reentry
Space debris poses a risk to humans when it falls to the ground, to infrastructure and to the environment – some can carry toxic, flammable or radioactive materials. Another growing concern is the possibility of large debris hitting aircraft in flight.
However, predicting the timing and trajectory of reentry is extremely difficult. Existing ground-based radar and optical tracking systems struggle to monitor them once they begin to disintegrate in the atmosphere.
“The problem right now is that we can track things very well in space. But once it gets to the point where it is actually disintegrating in the atmosphere, it becomes very difficult to track,” explains Fernando.
By analyzing data from 127 seismometers, the researchers calculated the trajectory and speed of the module, which with approximate dimensions of 1 meter wide and weighing more than 1.5 tons, re-entered the atmosphere in April 2024.
The seismic signals also allowed us to infer how the object fragmented in a cascade, generating multiple sonic explosions as it descended.
Real-time monitoring of falling satellites
“Near real-time” tracking – according to the authors – will help authorities quickly recover objects that reach the ground, which is especially important because they can carry harmful substances. The ultimate goal is to achieve velocity, direction, and fragmentation estimates within minutes, or even seconds, of reentry.
In an analysis paper, Chris Carr of Los Alamos National Laboratory says more research is needed to reduce the time between an object’s re-entry into the atmosphere and determining its trajectory. However, the method described “makes it possible to quickly identify debris fall areas”, a capability that will be increasingly relevant given the sustained increase in the number of satellites in orbit and, with it, space debris.
FEW (EFE, AP)
