The Defense Advanced Research Projects Agency (DARPA) has revealed Earth’s atmosphere can serve as a powerful sensor, allowing the detection and modeling of events on the ground and in space with incredible precision.
Once thought impossible, the new sensor capabilities unveil the ability to follow energy from their beginnings as small-scale, meters-wide disturbances as they propagate over much greater distances “and potentially around the world,” according to Michael “Orbit” Nayak, program Manager with DARPA’s Atmosphere as a Sensor (AtmoSense) program.
Launched in 2020, DARPA’s AtmoSense program began with a straightforward goal: understanding the dynamics of energy propagation between Earth’s surface and the ionosphere, and whether they could be leveraged as a sensor system.
Over the last several years, the program has refined its ability to detect and model energy waves—both acoustic and electromagnetic—moving through Earth’s atmosphere, paving the way toward new scientific applications, as well as those with national security implications.
The agency plans to share its findings in the coming weeks during a workshop later this month in Daytona Beach, Florida, wher DARPA officials and researchers will showcase key breakthroughs from the program’s efforts with members of the defense and scientific communities.
DARPA is ‘AtmoSensing’ Energy from the Ground Up
From the outset, the AtmoSense program team had set out to determine whether atmospheric wave propagation might be useful for unveiling critical details about events occurring on Earth, including their source and scale.
“High-resolution surface-to-space simulation of acoustic waves was considered impossible before the program began, but we accomplished it,” said Nayak in a recent statement. With the development of models that cover six orders of magnitude in scale, Nayak and his team say they were able to demonstrate how energy begins with small disturbances on the ground, eventually propagating through the atmosphere. Such events remain detectable up to thousands of kilometers away from their point of origin.
“We used to call the ionosphere the ‘ignorosphere,’ but AtmoSense made some key interdisciplinary breakthroughs to address what used to be a massively intractable problem,” Nayak said.
Additionally, the open-source tools developed by the program are now allowing researchers to model complex behaviors exhibited by atmospheric energy waves in 3D. This capability could allow for the detection of illicit underground explosions produced during secretive weapons testing, or other covert activities from afar—using nothing more than atmospheric signals.
Validation Through Controlled Detonations
Unfolding across two primary phases, AtmoSense first focused on modeling large Earth-based events like earthquakes and volcanic eruptions. Then, beginning last year, the second phase of the program involved field testing carried out in New Mexico, where a series of controlled detonations were undertaken that included eight 1-ton blasts and a pair of 10-ton blasts.
By monitoring these detonations, the researchers were able to validate their predictive models, which were shown to closely match both ground-based and airborne sensor data.
Even beyond the new understanding of upper-atmosphere dynamics that AtmoSense has provided, as well as the program’s potential for tracking large-scale Earth-based events, the program also showcases some key advancements which could play an important role in supercomputing and modeling for complex systems.
Nayak says that such capabilities may be useful in modeling hypersonic flight, as well as certain fluid dynamics simulations and other demanding scientific challenges where difficult computational models are required.
An Unexpected Discovery: Tracking Objects Entering Earth’s Atmosphere
The AtmoSense program also made some surprise discoveries since its inception in 2020. Among the most surprising had been when research team members say they detected a significant dip in electron content throughout the atmosphere following one of its test detonations in New Mexico.
Investigating the strange loss of electrons, the team traced the disturbance back to a SpaceX Falcon 9 re-entry, which had occurred at almost the same time as their test. Employing additional analysis during subsequent Falcon 9 reentries revealed a pattern: electron content drops appeared to happen during each reentry, revealing a new method for detecting objects as they enter Earth’s atmosphere.
One of the most surprising findings emerged when researchers detected a significant dip in atmospheric electron content following one of the test detonations. Upon investigation, the disturbance was traced to a SpaceX Falcon 9 re-entry that coincided with the test. Further analysis of multiple Falcon 9 re-entries confirmed a repeatable pattern in electron content drops, revealing a new method for detecting objects re-entering Earth’s atmosphere.
This unexpected breakthrough was led by a team from Embry-Riddle Aeronautical University in collaboration with Computational Physics, Inc., and has been submitted for peer-reviewed in advance of publication.
DARPA Plans to Expand the Sensing Horizon
Overall, the AtmoSense program has already demonstrated that energy wave modeling can go beyond detecting surface-level disturbances, allowing the tracking of atmospheric and space-based activity that has potential significance to national security.
As such, future applications for the program may reveal AtmoSense to be more than just a scientific milestone, but a foundational capability for a new era of global sensing and strategic awareness.
In the near term, AtmoSense is already showing promise in aerospace technology, physics, and other fields, with potential for “other big-compute ideas we haven’t even considered yet,” Nayak said.
“That’s what I’m most excited about uncovering at our April event,” he added.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.