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US satellite protection plan global radio threat

Monday 14 August 2006

US satellite protection scheme poses global communications threat

- International community needs to consider unintended effects of using system -

A proposed US system to protect satellites from solar storms or high-altitude nuclear detonations would cause worldwide radio communications blackouts, according to new research by a group of scientists from New Zealand, Finland and the UK.

If activated, the envisaged “radiation belt remediation” system would significantly alter the upper atmosphere in the short term, seriously disrupting high frequency (HF) radio wave transmissions and GPS navigation around the globe, says the group’s lead researcher, Dr Craig Rodger of the University of Otago Physics Department.

The remediation system aims 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 high-altitude nuclear explosions or powerful solar storms, says Dr Rodger.

The approach, which is being considered by the US Air Force and the US Defense Advanced Research Projects Agency, involves using very low frequency radio waves to flush particles from belts and dump them into the upper atmosphere over either one or several days.

“We’ve calculated that Earth’s upper atmosphere would be dramatically affected by such a system, causing unusually intense HF blackouts around most of the world,” he says.

“Airplane pilots and ships would lose radio contact and some Pacific Island nations could be isolated for as long as six to seven days, depending on the system’s design and how it was operated,” he says.

GPS would likely also suffer large-scale disruptions, as signals between ground users and satellites were scrambled by the ionosphere, he added.

The disruptions result from a deluge of dumped charged particles temporarily changing the ionosphere from a “mirror” that bounces high frequency radio waves around the planet to a “sponge” that soaks them up, he says.

In their paper, just published in the August edition of the international journal Annales Geophysicae, the Otago researchers and UK and Finnish colleagues suggest that policymakers need to carefully consider the implications of remediation.

“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, regardless of the side effects we foresee.

“However, the case for using the system to mitigate the lesser risk to satellites from charged particles injected by naturally-occurring solar storms needs to be considered more closely. Here, the impact of the disruption to global communications should be weighed carefully against the potential gains,” says Dr Rodger.

The researchers also calculated the likely effect of remediation on the ozone layer, but found that ozone depletion would be short-lived and similar to that resulting from natural processes such as large solar storms and volcanic eruptions.

The paper, titled: “The atmospheric implications of radiation belt remediation” was co-authored with Otago colleague Associate Professor Neil Thomson and researchers from the British Antarctic Survey, and the Sodankylä Geophysical Observatory in Finland and the Finnish Meteorological Institute.


Notes and Background


For more information on the threats to satellites posed by high altitude nuclear explosions visit:

The site features a copyrighted article which originally appeared in Scientific American magazine in June 2004 entitled "Nuclear Explosions in Orbit", and has been reprinted with the permission of the author. The article ends with several additional information sources.

It has been suggested that a nuclear airburst at high-altitude would significantly shorten the operational lifetime of Low Earth Orbiting satellites. Even a "small" detonation (~10-20 kilotons) occurring at altitudes of 125-300 km, could lead to the loss of 90% of all low-earth-orbit satellites within a month. In 2004 there were approximately 250 satellites operating in low-Earth orbit (LEO). These satellites fulfil a large number of roles, including communications, navigation, meteorology, military and science. In the event of a nuclear airburst at high-altitude, or an unusually intense natural injection, this large population of valuable satellites would be threatened. Due to the lifetime of the injected electrons, the manned space programme would need to be placed on hold for a year or more.

In the earliest days of the Space Age, the US "Starfish Prime" HANE, a 1.4 Megaton detonation occurring at 400 km above Johnston Island in the central Pacific Ocean on 9 July 1962, damaged 3 of the 5 satellites which operating in space at the time. This included the world's first active communications satellite, Telstar, which failed due to radiation exposure, even though the satellite was launched after the Starfish Prime explosion.

HF Communications
HF radio frequencies are very important because of their wide uses. Many developed countries use HF for radiocommunications to and from aircraft and ships, international broadcasting, amateur operations, and for fixed long-distance radiocommunications. While little use is made of HF radiocommunications in developed countries for domestic communications, lesser developed countries still find HF cost-effective for their domestic radiocommunications needs, such as for national broadcasting, mobile, and fixed point-to-point communications.

The Global Positioning System, usually called GPS, is the only fully-functional satellite navigation system. A constellation of more than 24 GPS satellites broadcasts precise timing signals by radio to GPS receivers, allowing them to accurately determine their location (longitude, latitude, and altitude) in any weather, day or night, anywhere on Earth. GPS has become a vital global utility, indispensable for modern navigation on land, sea, and air around the world, as well as an important tool for map-making and land surveying. GPS also provides an extremely precise time reference, required for telecommunications and some scientific research. The operation of an RBR system would lead to serious GPS degradation at mid latitudes, a new and unexpected experience for mid-latitude GPS users.


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