US satellite plan 'will knock out Pacific radio links'

Pacific Island nations -- and airline pilots around the globe -- could lose high frequency radio links for up to a week if the US goes ahead with a plan to protect its satellite network, Otago University researchers said today.

They warned the Americans plan to protect its satellites from both natural radiation and "airbursts" of nuclear weapons posed a global communications threat.

The US Air Force and the US Defence Advanced Research Projects Agency (DARPA) have proposed using very low frequency radio waves to flush particles from radiation "belts" above Earth and dump them into the upper atmosphere over either one or several days.

This deluge of dumped charged particles would temporarily change the ionosphere from a "mirror" that bounced high frequency radio waves around the planet to a "sponge" that soaked them up, Dr Craig Rodger of Otago University's physics department, said today.

The ionosphere is one of the highest layers of the Earth's atmosphere, starting at about 70km and continuing out to about 640km, and contains ions created when solar radiation tears electrons off atoms in the atmosphere. It is important for reflection of some radio waves.

Dr Rodger, lead researcher on a multinational study also involving scientists from Finland and Britain, said plane pilots and ships would lose radio contact and some Pacific Island nations could be isolated for up to a week, depending on the system's design and how it was operated.

He said GPS services would also likely suffer large-scale disruptions, if signals between ground users and satellites were scrambled in the ionosphere.

The US "radiation belt remediation" was intended to protect hundreds of low earth-orbiting satellites from having their onboard electronics ruined by charged particles in unusually intense radiation belts "pumped up" by powerful solar storms -- or small nuclear weapons deliberately exploded in the atmosphere to disrupt communications.

"Earth's upper atmosphere would be dramatically affected by such a system, causing unusually intense high-frequency (radio) blackouts around most of the world," Dr Rodger said.

The researchers, whose work is published work in August edition of the international journal Annales Geophysicae, called for policymakers to carefully consider the implications of the US scheme.

"If the intense radiation belts resulted from a rogue state detonating a nuclear-tipped missile in the upper atmosphere, using such remediation technology would probably be acceptable to the international community," they said.

But the case for using the system to mitigate the lesser risk to satellites from charged particles injected by naturally-occurring solar storms needed to be considered more closely and weighed against the impact of the disruption to global communications.

Many developed countries use HF radio for communicating with aircraft and ships, international broadcasting, amateur radio, and fixed long-distance communications, and developing countries use it for domestic links - national broadcasters and both mobile and fixed point-to-point communications.

The researchers also considered whether the changes to atmospheric chemistry would harm the ozone layer, but found that ozone depletion would be short-lived.

- NZPA