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 WASHINGTON
- President Bush has ordered plans for temporarily disabling
the U.S. network of global positioning satellites during
a national crisis to prevent terrorists from using the
navigational technology, the White House said Wednesday.
Any shutdown of the network inside the United States would
come under only the most remarkable circumstances, said
a Bush administration official who spoke to a small group
of reporters at the White House on condition of anonymity.
The GPS system is vital to commercial
aviation and marine shipping.
The president also instructed the Defense
Department to develop plans to disable, in certain areas,
an enemy’s access to the U.S. navigational satellites
and to similar systems operated by others. The European
Union is developing a $4.8 billion satellite navigation
program called Galileo, which will stay active during
a U.S. GPS disruption.
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| A
GPS reading from the North Pole from a surfaced U.S.
Ohio-class SSBN ballistic nuclear missile submarine.
(North 89.56°) |
Clearly A Big Deal
The military increasingly uses GPS technology to move
troops across large areas and direct bombs and missiles.
Any government-ordered shutdown or jamming of the GPS
satellites would be done in ways to limit disruptions
to navigation and related systems outside the affected
area, the White House said.
“This is not something you would
do lightly,” said James A. Lewis, director of technology
policy for the Washington-based Center for Strategic and
International Studies. “It’s clearly a big deal.
You have to give them credit for being so open about what
they’re going to do.”
GPS is based on a constellation of 24
solar-powered orbital satellites about 12,500 miles above
the Earth. A GPS receiver on the ground seeks tracking
signals from at least three satellites, then interpolates
the data to establish latitude and longitude. If a device
can pick up four or more signals, it can also determine
a user's altitude.
The U.S. military originally built NAVSTAR,
as they called it. The first satellite was launched in
1978 and the system was fully operational by the early
1990s. Originally, the military programmed the system
for "selective availability," which gave the
military 10-meter precision and civilians 100-meter precision.
Selective availability was eliminated in 2000. The latest
GPS transmitters are built under MILSTAR II protocols,
which means that the signals can be automatically disrupted
in time of war. This is the first time that the White
House has said they could and would be disrupted outside
of a nuclear missile wartime exchange.
Users can get accurate location information
across the globe, and most equipment can interpret it
to provide speed, distance to a destination and even exact
local sunrise and sunset times. Devices are installed
in most large ships and aircraft, and the FAA has incorporated
GPS as a key part of instrument flight. Many cars use
it, and transit companies use it to track trucks and buses.
Handheld devices are used by everyone from hikers to land
surveyors. The military has adapted bombs with GPS receivers
that can guide the weapons to targets.
With the military controls removed, GPS
users can now get a precise latitude and longitude to
within 10 to 15 meters. Advanced systems known as differential
GPS and the Wide Area Augmentation System incorporate
the use of stationary ground stations to interpolate signals,
and can offer accuracy of 1 to 3 meters or better. The
satellites have diagnostic systems and stop sending position
data if they're malfunctioning.
The U.S. Department of Defense continues
to run the system, though other federal agencies such
as the Department of Transportation have taken a role
in upgrading and maintaining it. The Coast Guard helps
maintain the civilian portions of the system, and private
satellite operators provide signals for some advanced
interpolation services. The government's Interagency GPS
Executive Board coordinates efforts.
President Clinton abandoned the practice
in May 2000 of deliberately degrading the accuracy of
civilian navigation signals, a technique known as “selective
availability.”
The White House said it will not reinstate
that practice, but said the president could decide to
disable parts of the network for national security purposes
at a moment's notice.
Part of space policy
The directives to the Defense Department and the Homeland
Security Department were part of a space policy that Bush
signed this month. It designates the GPS network as a
critical infrastructure for the U.S. government. Part
of the new policy is classified; other parts were disclosed
Wednesday.
The White House said the policies were
aimed at improving the stability and performance of the
U.S. navigation system, which Bush pledged will continue
to be made available for free.
The U.S. network comprises more than
two dozen satellites that act as beacons, sending location-specific
radio signals that are recognized by devices popular with
motorists, hikers, pilots and sailors.
Bush also said the government will make
the network signals more resistant to deliberate or inadvertent
jamming.
Tony's Note: Don't count on GPS
to work if the chips are ever down. If a National Emergency
occurs, count on the system to actually display wrong
information, or none at all, and abandon reliance on GPS
completely.
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