Re: [FT] Some thinking on sensor and operational level games

G'day guys,

Sorry this isn't exactly on topic, but thought you might be interested
to 
hear how effective passive sensors can be (probably old news to many of 
you, but I thought it was cool).

This was on the cnn site earlier this week

Cheers

Beth

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WASHINGTON (AP) -- America's stealth bombers may be in danger of having 
their cover blown by a new type of radar that uses cell phone
technology, 
researchers say.

The Air Force says it's a limited problem and America's unique stealth 
fleet is in no danger. Yet U.S. intelligence reports label the radar a 
serious threat, and several scientists agree.

  "We're talking about radar technology that can pinpoint almost any 
disturbance in the atmosphere," said Hugh Brownstone, a physicist at the

Intergon Research Center in New York who has worked for the cell phone 
giant Nokia.

"You might not be able to distinguish between a stealth plane and a
normal 
one, but you might not need to. The point is, you can see the stealth
plane 
as a blip."

The potential risk comes from the towers used by cell phone companies to

draw in signal patterns. The new technology, called passive radar,
watches 
signals from common cell phone transmissions. When a plane passes
through, 
it leaves a hole in the pattern, giving away its location.

Traditional radar -- the kind stealthy B-2 and F-117A bombers can fool 
with  their angles and radar-absorbing paint -- sends out signals and
waits 
for them to bounce off large objects in the sky and return.

Some aviation experts suspect the Serbs used a rough version of passive 
radar -- plugging computers into their existing air defense system -- to

locate an F-117A Nighthawk stealth bomber, shot down in 1999.

There are more than 100,000 cell phone towers and other sites within the

United States. Industry analysts estimate there are 210,000 sites in 
Europe. The rest of the world is unevenly covered, but even the smallest

and poorest nations often have several cell phone towers.

The passive radar system has drawbacks. It can't effectively pinpoint 
whether a plane is indeed a stealth plane or some other aircraft, 
scientists say. It's also much more difficult to make work.

"The success rate of these systems is just below the success rate of 
traditional radar," said Air Force Capt. Eric Knapp.

A major hurdle is the complex math necessary to translate cell phone 
signals into easy-to-understand blips that move across a computer
screen. 
Without the computer programming to make sense of the cell phone
signals, 
it would be impossible to fire a missile at a plane.

Still, the passive radar technology is basically sound, said Nick Cook,
an 
aerospace consultant for Jane's Defence Weekly.

"It needs further work, but the theory is there," he said. "Still it
would 
be some time before I could imagine something like this compromising 
stealth technology completely."

John Hansman, professor of aeronautics and astronautics at the 
Massachusetts Institute of Technology, said passive radar is still in
its 
"infancy, but is something that will lead to new stealth research."

"This is another trick that will force stealth researchers to push 
forward," Hansman said.

The British defense contractor Roke Manor Research is in the forefront
of 
passive-radar technology.

Peter Lloyd, head of research there, said, "We would be utilizing 
technology that we already have available. The mobile telephone base 
stations would not have to be altered at all. "

His company's Web site claims existing stealth technology already has
been 
rendered obsolete.

Brownstone believes China, Japan and Russia already have passive radar
in 
various stages of development. He is concerned that those countries
might 
sell the technology to smaller countries that are hostile to the United 
States.

Keeping stealth planes safe from enemy radar has always been a 
back-and-forth contest, pitting American ingenuity against developing 
concepts in radar.

The F-117A, developed in great secrecy in the 1970s, was not disclosed 
until 1988. It saw its first combat in the 1989 invasion of Panama and
was 
a star of the 1991 Gulf War.

The B-2 bomber, which saw its first combat in NATO airstrikes against 
Yugoslavia, uses stealth technologies that are more advanced than the 
F-117A's. An even newer version of stealth is used in the F-22 fighter
now 
in development. No other country has stealth aircraft in active use, 
although Russia and others have researched the idea.

Six of the $2 billion B-2s, in their first combat use, flew about 50
secret 
missions out of a total 30,000 NATO bombing runs over Kosovo in 1999.
They 
dropped about one of every 10 bombs in the campaign.

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Elizabeth Fulton
c/o CSIRO Division of Marine Research
GPO Box 1538
HOBART
TASMANIA 7001
AUSTRALIA
Phone (03) 6232 5018 International +61 3 6232 5018
Fax 03 6232 5053 International +61 3 6232 5053