Protecting hundreds of low-Earth-orbit satellites from destruction seems a laudable idea, and the US Pentagon wants to do just that. But the scheme could backfire, by shutting down civilian and military communications and impairing Global Positioning System signals.
The Pentagon is concerned that a high-altitude nuclear explosion or an intense solar storm could fill near-Earth space with charged particles, crippling the operation of many satellites. It has proposed a plan called “radiation belt remediation” to clean it up.
The idea is to orbit satellites that would direct very low frequency radio waves at 20 kilohertz into areas filled with charged particles. That would create wave-particle interactions that encourage particles to precipitate and fall into the upper atmosphere, where they would do little damage to other satellites in low-Earth orbit.
However, a study by Craig Rodger at the University of Otago in New Zealand, and colleagues, has revealed this could affect the electrical properties of the part of the upper atmosphere called the ionosphere, which in turn could severely disrupt radio and GPS transmissions.
Global-level effects
Normally the ionosphere reflects radio waves at frequencies up to about 30 megahertz, allowing signals from one point on the ground to be reflected to another point located a great distance away.
But an ionosphere full of charged particles would absorb radio signals instead. That would shut down long-distance transmission in the 3 to 30-megahertz high-frequency band used by military and civilian communications, Rodger warns.
Those frequencies are important for international aviation and also include the short-wave bands used by amateur radio operators.
Absorption at higher frequencies could degrade the signal quality and accuracy of the Global Positioning System, he reports.
He says the benefits of the Pentagon’s scheme must be weighed against the risks. For a natural solar storm, the damage to satellites is expected to be relatively minor. "It’s not clearly an emergency, and it’s going to have global-level effects" by shutting down communications.
But the charged-particle boosting effect of a nuclear attack could render orbiting satellites completely useless. "If somebody detonated a nuke, you would turn the system on anyway, because the choice is losing 250 satellites or disrupting communications for a week," Rodger says.
From NewScientist
