Researchers from Los Alamos National Laboratory have presented a new method for tracking objects, including uncontrolled space debris, entering Earth’s atmosphere, using ground-based seismic sensors rather than optical and radar tracking or other costly, complex approaches.
The new approach could assist efforts to alert people on the ground about falling space debris that could pose a danger to property and individuals.
Dangers Rising from an Increasing Population of Falling Objects entering Earth’s Atmosphere
Since the Soviet Union launched humanity’s first spacecraft in 1957, thousands of satellites and other objects have been rocketed into Low Earth Orbit (LEO). As the population of space-based objects has grown, incidents of falling debris causing damage on the ground have increased. These incidents are only expected to increase as LEO continues to fill up.
While the kinetic effects of falling debris can be catastrophic, the Los Alamos researchers note that uncontrolled re-entry of spacecraft can pose additional threats. For example, a spacecraft carrying radioactive materials could pose a larger danger than a single crashed satellite. Many of these crafts also contain toxic and flammable materials, further increasing the potential hazards posed by their re-entry.
Unfortunately, predicting when and where such events will occur is extremely difficult. The problem is compounded by limitations in ground-based radar and optical tracking systems designed to monitor LEO for potential threats, since these objects begin to disintegrate as they enter the atmosphere.
These limitations motivated Los Alamos scientists Benjamin Fernando and Constantinos Charalambous to look for alternative methods to track disintegrating objects and predict when and where they might strike land.
Tracking the Reentry of Shenzhou-15 Reentry Confirms New Approach
According to a statement detailing the team’s novel debris-tracking approach, they began by examining publicly available data from ground-based seismic sensors to search for signs of shockwaves, or sonic booms, caused by reentering debris. As a test case, they focused their search on the April 2024 reentry of China’s large and heavy Shenzhou-15 orbital module.
Before its reentry, the abandoned module had been in a decaying orbit that regularly passed over many population centers around the globe. The falling object’s sheer size and toxic material components stoked fears that its eventual reentry could be catastrophic.
After scanning seismic sensor data from sensors placed throughout Southern California and Nevada, the team spotted the telltale sonic booms of Shenzou-15’s atmospheric reentry. Using mathematical models, the team successfully interpolated the arrival times of the largest shockwaves from the module’s reentry at different locations across the southern US.
The team said that this data allowed them to estimate Shenzhou-15’s altitude, speed, and ground track with surprising accuracy. Specifically, the observed reentry location and the Tracking and Impact Prediction estimate, which placed the landing spot somewhere in the Atlantic Ocean, were 8,600 kilometers apart.
The data also revealed that the module did not fall in a single event but instead fragmented over time into progressively smaller pieces. Notably, the team said that the spacecraft’s breakup matched eyewitness reports.
Unlocking the Rapid Identification of Debris Fall-Out Zones
When discussing potential applications of their novel seismic reentry-tracking approach, the Los Alamos team said this technology could be used to track debris on the ground after impact, aiding search-and-recovery efforts. The approach could also help scientists track the spread of smaller hazardous particles in Earth’s atmosphere, which they call “crucial for recovery and contamination mitigation.”
Scientist Chris Carr noted that further research will be needed to shorten the time needed to calculate an object’s trajectory once its sonic booms and shockwaves have been detected. However, Carr also praised the Los Alamos team’s method, stating that Fernando and Charalambous’ approach “unlocks the rapid identification of debris fall-out zones, which is key information as Earth’s orbit is anticipated to become increasingly crowded with satellites, leading to a greater influx of space debris.”
The study “Reentry and disintegration dynamics of space debris tracked using seismic data” was published in Science.
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.