Satellite protection scheme threatens radio comms

Boffins worried

A scheme designed to protect the Earth's communications infrastructure from an excess of highly charged particles in orbit could lead to communications blackouts across the globe lasting for up to 10 days, according to scientists at the British Antarctic Survey (BAS).

Conditions in Earth's orbit are hostile at best, and satellites are at particular risk if something should cause an influx of high energy particles into the Van Allen radiation belts, zones around the planet with already high levels of energetic particles.

In the event of a high altitude nuclear explosion, for instance, the Van Allen belts would become so dangerous to satellites that up to 90 per cent of those in low earth orbit could be disabled within a month, according to researchers. Solar activity is also known to increase the number of particles in the belts, and has been known to damage expensive communications equipment.

The US has come up with a scheme to deal with this excess of particles, called "radiation belt remediation" (RBR), but researchers at BAS warn it could have unintended consequences.

"The easiest way to get rid of these particles is to dump them into the Earth's atmosphere, and the US is investigating techniques to do that," BAS scientist Dr Mark Clilverd said. "They propose using very low frequency (VLF) radio waves to interact with the particles, and dump them into the atmosphere."

The US is planning to launch a satellite as soon as 2008 to begin experimenting with the technique.

"When we heard of the plan to bombard the atmosphere with high energy particles, we though it was important to investigate," he told us. So the team, including scientists from Finland and New Zealand, tackled the problem from a theoretical perspective.

But Dr Clilverd and his colleagues are concerned that although people would probably be very understanding about using such technology after an unexpected nuclear detonation, more widespread use is unlikely to be forgiven, given the consequences he and his team are predicting.

The researchers calculate that Earth's upper atmosphere could be dramatically affected by such a system, causing unusually intense high frequency radio blackouts around most of the world.

"Solar activity does cause particles to rain down on the atmosphere, but the effects tend to be confined to the poles. The inner Van Allen belts we are talking about extend from the mid latitudes right down to the equator, so we are talking about the populated areas of the world suffering radio blackouts lasting for as long as the RBR system was operating.

"Some planes and ships that rely on HF communications could lose radio contact, and some remote communities that also depend on HF could be isolated for as long as six to seven days, depending on the system's design and how it was operated.

"GPS signals between ground users and satellites would also be disrupted as they pass through the disturbed ionosphere," he added.

Instead, Clilverd suggests that satellites should be engineered to cope with more extreme conditions, although he concedes that this would add both weight and cost to the build process. ®

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