A Sandia Labs scientist specializing in tracking the angle of objects entering Earth’s atmosphere has demonstrated how an existing network of infrasound technology-based sensors designed to detect potential nuclear weapon tests can be adapted for planetary defense.
The novel use of this technology can provide a defense against potential dangers from outer space, including discarded tools, defunct satellites, and other pieces of space junk currently encircling the planet.
With future missions expected to add to the volume of hazardous material that may cause damage when falling back to Earth, and diplomatic efforts to solve the problem still ongoing, using infrasound technology to determine where and when an object is likely to impact could prove increasingly valuable. This technology could also protect against natural objects like falling meteors or potentially against objects launched intentionally at a ground target in a future space war.
How Infrasound Technology Aids Planetary Defense Against Incoming Space Objects
In an email to The Debrief, Sandia Labs scientists Elizabeth Silber explained how the infrasound technology behind the Comprehensive Test Ban Treaty Organization (CTBTO) worldwide sensor network works.
“The CTBTO’s worldwide network of infrasound sensors is designed to detect minute disturbances in the atmosphere, including signals from events occurring thousands of kilometers away,” Silber explained. “These sensors are highly sensitive by design. Their effectiveness lies in their ability to register very subtle atmospheric pressure changes caused by distant, impulsive sources.”
In the same email, Silber said that her curiosity was initially piqued by the fact that the CTBTO network and NASA’s Center for Near Earth Object Studies (CNEOS) database would often identify slightly different locations for a bolide, or a meteor exploding as it enters the atmosphere. Described by Silber as “one of the most important existing resources” for studying these types of events, NASA’s CNEOS database contains records of around 1,000 atmospheric events detected by U.S. government space-based sensors.
Because the two systems use different technologies, Silber wondered if the data captured by the infrasound technology-based sensors could offer additional information that was confusing the NASA network. Specifically, the Sandia Labs scientists said she looked at how a fireball’s path through the atmosphere, particularly the object’s angle of entry, might explain the mismatched readings.
“Shallow entries travel longer distances and can send out sound from many points along the way, which can throw off the apparent direction of the signal by several degrees,” Silber told The Debrief. “Steeper entries are much more straightforward.”
A press release announcing the research said that using this data to pinpoint potential impact locations more accurately is critical and could play a vital role in planetary defense.
“If you don’t know where something is going, then you have a hard time preparing for it,” the release explained.
Predicting the Path of Entry for Space Objects
Silber developed a customized computer model to test the hypothesis to show how these different atmospheric entry trajectories affect what the infrasound systems “see.” Called BIBEX-M, or the Bolide Infrasound Back-Azimuth Explorer Model, Silber says her customized model uses the subtle variances in sound detected by the CTBTO sensors to calculate the likeliest path of meteors, pieces of space debris, or even planned reentry events “which follow similar extended paths.”
“Understanding this effect helps us better locate where these events happen, and makes global monitoring more accurate,” she explained.
In a published study detailing the findings, Silber said objects entering the atmosphere at angles above 60 degrees were the most likely to give different locations depending on the sensors used to track them. Because infrasound technology tracks signals over time, they are uniquely equipped to calculate entry angles and locations.
When asked how much advanced warning time this application of infrasonic technology could provide to people in potential impact locations, Silber said that the lead time before atmospheric entry events varies widely. For example, the Sandia scientist noted how in 2013 the 18-meter-wide Chelyabinsk asteroid went undetected right up until it entered the atmosphere because it was approaching Earth from the direction of the Sun. Another cited example was the Ribbeck fireball over Germany in 2024, which Silber says wasn’t detected until approximately three hours before entry.
Unlike natural events, Silber told The Debrief that artificial objects returning to Earth from interplanetary missions have precisely calculated trajectories known “far in advance.” Along with successful, coordinated reentry tracking campaigns like NASA’s Stardust and Genesis missions and the Japan Space Agency (JAXA) Hayabusa and Hayabusa2 sample-return missions, Silber cited the 2023 atmospheric reentry of NASA’s OSIRIS-Rex mission as examples of multiple sensors working together to determine accurate reentry coordinates. That event, she explained, was the “largest geophysical observation to date, leveraging a wide range of ground-based and atmospheric sensors,” including those based on infrasound technology.
“These campaigns provide a rare opportunity to validate and refine our detection capabilities under controlled conditions,” Silber told The Debrief.
Improving Object Tracking with Newer Technologies
Although tracking smaller objects is still the most significant challenge for any sensor systems involved, Silber said that predicting the orbits of some of the largest and most dangerous objects in space can occur “decades in advance.” She also said that efforts to improve early detection of smaller objects are “ongoing.”
When asked if there are potential ways of improving the planetary defense capabilities beyond CTBTO infrasound technology, Silber offered several examples.
“This is a great question!” she replied. “While the global ground-based network remains the backbone of atmospheric monitoring, there is growing interest in complementary technologies to enhance planetary defense capabilities.”
According to Silber, high-altitude platforms, such as stratospheric balloons equipped with infrasound sensors, “have shown significant promise.” For example, balloons carrying infrasound sensors operating at these extreme altitudes captured clear infrasound signals from the OSIRIS-Rex reentry. This success, the scientist noted, demonstrated the technology’s potential to monitor high-altitude atmospheric events “with remarkable sensitivity.”
When asked about planned improvements to the existing infrasound CTBTO system, Silber told The Debrief that the organization operating and maintaining the sensors would best answer the question. However, she said the system undergoes regular maintenance, just like “any sophisticated global monitoring system.” She also noted that continued advances in all sensing and signal processing areas could also improve systems using infrasonic technology.
Ultimately, the Sandia scientist says her findings are important because they are the first to quantify the difference between sensor readings that can be attributed to any incoming object’s trajectory. She also said the work offers researchers studying planetary defense efforts a new tool to protect from space debris by scanning for infrasound signals “out to distances of 15,000 kilometers.”
“The results show that for shallow-entry fireballs, the common assumption of a single point source doesn’t always hold, even at long range,” Silber told The Debrief. “This has important implications for how we interpret infrasound data from both natural fireballs and space debris reentries, leading to more accurate event localization and improved global monitoring.”
Silber’s research paper “Investigating the relationship between bolide entry angle and apparent direction of infrasound signal arrivals” and the BIBEX-M tracking model were presented in full during a special session of the European Geophysical Union General Assembly 2025, which took place from 27 April to 02 May 2025.
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.