An Air Force Research Laboratory mission to study the impact of Van Allen belt radiation on satellites could pave the way for more military and civilian spacecraft to fly safely in the harsh environment of medium Earth orbit.
Most of today’s satellites either fly in geostationary orbit about 22,000 miles out, or in low Earth orbit below about 1,200 miles. Few vehicles fly in between those ranges, because radiation from Van Allen’s “inner” and “outer” belts is high there, making medium Earth orbit particularly hazardous for spacecraft.
Now, two AFRL satellites are working together to measure and map radiation in that zone and study the impacts on spacecraft components. That data will help in developing new radiation-hard electronics for vehicles to operate there.
The satellites are also studying the interaction between very low frequency radio waves and particles in the Van Allen belts, which could provide critical insight into the potential of VLF waves to mitigate intense radiation from a nuclear explosion.
That’s something the AFRL has been working on for at least 15 years, and for the military, it’s the primary mission of the dual-satellite experiments currently underway, said Michael Starks, a lead scientist at AFRL’s Space Vehicles Directorate and program manager for the Radiation Belt Remediation program.
“That’s the heart of the mission,” Starks told the Journal. “If you set off a nuclear weapon above 50 kilometers (about 31 miles), it creates a man-made radiation belt that’s a thousand times more intense than natural ones, and the impact on spacecraft is much worse. With today’s efforts to puts lots of satellites into low Earth orbit, we don’t want to lose them if someone does something irresponsible.”
The U.S. Department of Defense experienced the devastating effects of nuclear fallout on satellites during high-altitude missile tests in the Pacific Ocean in 1962.
“Those tests accidentally killed about a dozen satellites,” Starks said.
And as other countries have pursued ballistic technology, the DOD recognized high-altitude nuclear explosions as an emerging threat to spacecraft.
DOD research has since led to employing VLF waves as a potential defense, because they can be used to clear away nuclear-induced radiation belts by basically pushing radioactive particles out of the magnetosphere.
“A nuclear radiation belt works the same as the Van Allen belts, where radiation generated by the sun is trapped by the Earth’s magnetic field,” Starks said. “The particles, or electrons, go away when they run into our atmosphere and get lost.”
VLF waves can “de-trap” particles in a nuclear radiation belt by scattering them.
“The VLF wave comes through and causes the particle paths to change,” Starks said. “We can put exactly the right VLF wave at exactly the right point to scatter the radiation.”
To do that, the AFRL launched a Demonstration and Science Experiments, or DSX, satellite into medium Earth orbit in June 2019. It’s now studying radiation there and testing the performance of an antenna that emits VLF waves.
A second satellite – the Very Low Frequency Propagation Mapper, or VPM – was also placed into low Earth Orbit in February. That satellite collects and measures the VLF waves coming from the DSX.
Together, the two satellites are actively probing the response of Van Allen radiation belt particles to weak radio waves that could, in the future, be used to “wash out” nuclear radiation, said DSX principal investigator James McCollough.
Kevin Robinson-Avila covers technology, energy, venture capital and utilities for the Journal. He can be reached at email@example.com.