June 15, 2001. Copyright 2001. Graphic News. All rights reserved.

Stealth aircraft ÒuncloakedÓ by mobile phone technology 

LONDON, June 15, Graphic News: AmericaÕs multi-billion-dollar stealth bombers could be rendered obsolete by a British invention that uses existing mobile-phone base stations to detect and track aircraft that were previously invisible to radar.

The discovery was made by scientists at SiemensÕ Roke Manor Research site, who have developed equipment and software which, when used in conjunction with the base stations, make the planes visible again.

The angled surfaces of stealth aircraft are shaped to confuse conventional radar. A special paint absorbs radio waves and reduces the radar signatures of the $40 billion fleet of B-2 bombers and the older $6 billion fleet of F-117s to the equivalent of a bird in flight.

Peter Lloyd, head of projects at Roke Manor Research, said: ÒWe use just the normal phone calls that are flying about in the ether -- the U.S. military is very interested.Ó

Mobile-phone base stations are basically multi-channel, two-way radios which receive and pass on phone calls, generating low-power radio-frequency radiation.

The frequency is the rate at which the electromagnetic field changes direction and is given in Hertz (Hz), where one Hz is one cycle or wave per second, one megahertz (MHz) is one million cycles and one gigahertz (GHz) is one billion cycles per second. 

The environment is filled with radio-frequency radiation. Electric power has a typical frequency of 60 Hz, FM radio has a frequency of around 100 MHz and microwave ovens have a frequency of 2,450 MHz. 

New generation mobile networks, known as Universal Mobile Telecommunications Systems (UMTS) or third generation (3G) allow fast access to the internet on a mobile phone by constantly transmitting low-power radio-frequency radiation in the 28 GHz and 40 GHz wavelengths. It is in these bands of the radio spectrum that the new ÒpassiveÓ radar system works.

The Hampshire-based engineers, who have been involved in counter-stealth projects since 1986, discovered that this constant signal between phone masts creates an invisible screen that is broken whenever an aircraft passes through it.

Lloyd explained how the technology works: ÒWe would be utilising technology that we already have available. The mobile-telephone base stations would not have to be altered at all. If aircraft are flying over the area, signals that the base stations are sending into the air will be scattered on contact with the craft.Ó

The Roke Manor system uses receivers shaped like television aerials to detect the distorted signals. By combining these with signals from global positioning system (GPS) navigation satellites, a high-speed laptop computer can sort through the clutter of signals and calculate the position of a stealth aircraft to within 10 metres (33 feet).

According to military sources, a similar system may have been used in Serbia to shoot down a U.S. F-117A Nighthawk during a night mission in March, 1999. A barrage of Serb anti-aircraft missiles were fired into the area where the aircraft happened to be flying. It was the first time an F-117A had gone down in combat.

ÒIn the end you may have to redesign your stealth aircraft or think about adding jamming or other countermeasures,Ó says Dan Goure, a former Pentagon official who is a senior fellow at the Lexington Institute in Arlington, Virginia.

ÒIf you have not only the ability to do this kind of detection passively, but also to communicate the data to your military units, the way we use air power is going to have to change,Ò said Goure. ÒWe are simply not going to own the skies in the same way.
/ENDS

Sources: Siemens, Roke Manor Research, Reuters, Associated Press