14 August, 2006 Press releases

A proposed US system to protect satellites from solar storms or high-altitude nuclear detonations could cause side-effects that lead to radio communication blackouts, according to new research. If activated, the “radiation belt remediation” (RBR) system could significantly alter the upper atmosphere, seriously disrupting high frequency (HF) radio wave transmissions and GPS navigation around the world.

The remediation system aims to protect hundreds of low earth-orbiting satellites from having their onboard electronics ruined by charged particles in unusually intense Van Allen radiation belts “pumped up” by high-altitude nuclear explosions or powerful solar storms.

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

The scientific team from New Zealand, UK and Finland calculate that Earth’s upper atmosphere could be dramatically affected by such a system, causing unusually intense HF blackouts around most of the world.

Dr Mark Clilverd from British Antarctic Survey says, “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.”

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.

The research is published in the August edition of the international journal Annales Geophysicae. The researchers 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 any side effects. However, using the system to mitigate the lesser risk to satellites from charged particles injected by naturally occurring solar storms should be considered more closely. The impact of the disruption to global communications needs to be weighed carefully against the potential gains.

Issued by British Antarctic Survey Press Office on behalf of BAS, University of Otago in New Zealand, Sodankylä Geophysical Observatory in Finland and the Finnish Meteorological Institute.

Media enquiries to BAS Press Office. Athena Dinar – tel: +44 1223 221414, mob: 07740 822229, email: a.dinar@bas.ac.uk

The atmospheric implications of radiation belt remediation by Craig J Rodger, Mark A Clilverd, Thomas Ulich, Pekka T Verronen, Esa Turunen, Neil R Thomson is published in the August issue of Annales Geophysicae.

Dr Craig Rodger, University of Otago, New Zealand – tel: ++64 3 479 4120, email: crodger@physics.otago.ac.nz

Dr Mark Clilverd, British Antarctic Survey – tel: +44 1223 221541, email: m.clilverd@bas.ac.uk

Notes for Editors:

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 perform many 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.

The radiation belts were discovered by James A. Van Allen on Jan. 31, 1958, the first major scientific discovery of the early space age. He died last week (9 August) in Iowa City, at the age of 91. A Geiger counter on board the Explorer 1 satellite, developed by Dr. Van Allen, recorded two belts of charged particles trapped by Earth’s magnetic field. One belt is 400 to 4,000 miles above the surface, and the other is 9,000 to 15,000 miles high, both curving toward the magnetic poles. The Van Allen Belts remain a crucial area of study in space science, as evidenced by a recently announced, $100 million NASA project to study the effect of the belts on satellite communications and global navigation systems.

In the earliest days of the Space Age, the US “Starfish Prime” HANE, a 1.4 megaton detonation that occurred at 400 km above Johnston Island in the central Pacific Ocean on 9 July 1962, damaged 3 of the 5 satellites 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. The detonation also caused an electromagnetic pulse that shut down communications and electrical supply in Hawaii, over 1300 km away.

HF radio frequencies are very important because of their wide uses. Many developed countries use HF for radio communications to and from aircraft and ships, international broadcasting, amateur operations, and for fixed long-distance radio communications. Some countries still find HF cost-effective for their domestic radio communications needs, such as 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 broadcast precise timing, using 1.2-1.5 GHzradio signals, 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 could lead to serious GPS degradation at mid latitudes, a new and unexpected experience for mid-latitude GPS users.

British Antarctic Survey is a world leader in research into global issues in an Antarctic context. It is the UK’s national operator and is a component of the Natural Environment Research Council. It has an annual budget of around £40 million, runs nine research programmes and operates five research stations, two Royal Research Ships and five aircraft in and around Antarctica. More information about the work of the Survey can be found at: www.antarctica.ac.uk

The University of Otago is New Zealand’s oldest university. Located in Dunedin, Otago is the southern-most University of the country, with more than 17,800 students and 3300 staff. In New Zealand, universities are institutions where teaching is primarily undertaken by those engaged in research and scholarship. As New Zealand’s oldest university, Otago has a long established tradition of research excellence. Since its foundation in 1869, the University has steadily increased its teaching and research activities, while building on its original strengths, including Physics. More information on the University of Otago can be found at: www.otago.ac.nz.

The Sodankylä Geophysical Observatory is an independent research department of the University of Oulu, located in Lapland, and established in 1913 by Finnish Academy of Science and Letters to perform geophysical measurements and research based on the observation results. More information on Sodankylä Geophysical Observatory can be found at: www.sgo.fi.

The Finnish Meteorological Institute is the agency responsible for gathering and reporting weather data and forecasts in Finland. The Institute is an impartial research and service organisation with expertise covering a wide range of atmospheric science activities other than gathering and reporting weather data and forecasts. The main research subject of the Finnish Meteorological Institute is the Earth’s atmosphere. Other research topics include the study of near space and solar influence on the planet’s atmospheres. More information on the Finnish Meteorological Institute can be found at: www.fmi.fi.