DARPA‘s unique atmospheric listening experiment accidentally discovered a surprising phenomenon: SpaceX Falcon 9 rockets temporarily “turn off” some ionospheric electrons during their return to Earth. This discovery could be a new tool for tracking space objects and even identifying potential threats.
Atmosphere is a giant sensor
The U.S. Defense Advanced Research Projects Agency’s (DARPA) AtmoSense program uses the atmosphere as a global sensor. The goal is to capture acoustic and electromagnetic waves to detect events on the Earth’s surface, from explosions to natural disasters, and or threats to national security, such as the launch of intercontinental missiles. However, during testing in New Mexico, scientists made an unexpected discovery with unusual data: a sharp drop in the concentration of electrons in the upper atmosphere.
“Imagine a hose of water that is suddenly squeezed – the flow decreases dramatically. In the same way, a rocket passing through the ionosphere temporarily ‘displaces’ electrons,” explains Michael Nayak, project leader.
Falcon 9 trail
By comparing data from dozens of SpaceX launches, the team found that each Falcon 9 re-entry is accompanied by a similar effect. This opens up new possibilities for tracking spacecraft – even without traditional radars.
The discovery could help develop technologies to monitor unidentified objects re-entering the atmosphere, allow for more precise studies of the effects of rockets on the ionosphere, and could become part of a warning system for potential threats.
DARPA plans to present detailed results of the study at a workshop April 15-17. In the meantime, Falcon 9 continues to break records: more than 450 successful missions, each of which now leaves not only a trail of fire, but also an “electronic shadow”.
“We accidentally found a new way to ‘see’ spacecraft. But now we need to figure out how to use it for useful purposes,” Nayak adds.
We previously reported on how a Falcon 9 flight accidentally lit up the space station of the future.
According to darpa.mil
