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Satellites Play Crucial Roles in Air and Ground Battles

The war on terrorism will by fought from the air and on the ground and even with remote-control missiles, but all these efforts have one thing in common: They rely on satellites to find the enemy and provide secure lines of communication. "From a military point of view, space is the ultimate high ground," says Air Force Gen. Ralph E. Eberhart, SPACECOM commander in chief.

SPACECOM is military jargon for the U.S. Space Command, which coordinates all military and civilian "space assets." These include dozens of satellites that contribute directly or indirectly to U.S. military efforts, according to analysts.

Space is defined by SPACECOM as everything above 100 miles. Earth's atmosphere grows thinner with altitude in a gradual way, however. There is no clear edge. Pilots zooming above 50 miles are awarded astronaut wings, for example.

Most satellites, however, are at least 100 miles up with some ranging more than 22,000 miles above the surface. And military experts say the Armed Forces are relying more and more on these orbiting data and command posts to root out the enemy or to blow up targets with pinpoint accuracy from safe distances.

So as outer space increasingly becomes military space, SPACE.com presents this overview of how the military is commanding the skies and beyond.

The ultimate view

From 22,300 miles up, a satellite can see half the planet. That's where most missile-warning and communications satellites operate in what are called geosynchronous orbits -- perches that remain fixed over a given part of the planet by orbiting Earth once every 24 hours.

Weather satellites share this lofty region of space. Able to see half the globe, the GOES satellites of the National Oceanic & Atmospheric Administration feed constant data about cloud cover and moisture into weather forecasting programs. This information is also used by the military.

Some television satellites also operate at this altitude. Their fixed locations in the sky, relative to Earth, explains the fixed position of home satellite TV receiver dishes.

Various types of military communication satellites also traverse this high ground.

More critical at this extreme altitude are a handful of Defense Support Program (DSP) satellites, first deployed in 1970. They are a key part of the military's early warning systems, using infrared sensors to detect heat from missiles or rockets. Though the operation of these DSP satellites is kept secret, the Federation of American Scientists says three are in operation and two are in space and available as backups. The military claims it can spot any missile launch over 90 percent of the Earth's surface.

But there is a trade-off for the wide view offered from 22,300 miles up in space: an inability to see anything with high resolution. A host of other satellites, therefore, operate much closer to the planet.

Closer to Earth

Lower, around 10,900 miles above the surface, are 24 satellites that comprise the Global Positioning System, or GPS. Each satellite circles the planet once every 12 hours, and they combine to give near-total coverage of the globe. "GPS is absolutely critical to U.S. military operations," Eberhart says. The GPS system is also used commercially by pilots, boaters and hikers, and contributes to many rescues each year.

The GPS satellites emit constant signals, which when picked up by receivers in the air or on the ground can calculate time to within a billionth of a second, velocity within a fraction of a mile per hour and location to within a few feet, according to the Air Force. Five ground stations and four ground antennas, located around the world, coordinate the satellites and their signals.

GPS has allowed for dramatic improvement over previous attempts, such as in Desert Storm, to target missiles and bombs remotely. One new bomb, called Joint Direct Attack Munition, or JDAM, has a GPS receiver installed inside it and can be programmed to hit a target based on longitude and latitude. Since the JDAM finds the target, the crew doesn't have to, allowing them to fly at higher and safer altitudes. The Department of Defense has not discussed whether JDAM has been used in Afghanistan.

Lower still

A host of other satellites, providing intelligence imagery and weather data, are put into what's called Low Earth Orbit, typically between 100 and 300 miles up but as low as 80 miles and as high as 1,200 miles. Space shuttles and the International Space Station operate in Low Earth Orbit.

Several military spy satellites work in the 600-1,200 mile range. They're acronyms reflect the type of data they collect: electronic intelligence (ELINT); signal intelligence (SIGINT); and radar intelligence (RADINT). Spy satellites orbit at some 25 times the speed of sound, typically passing over a given location twice a day. This routine is useful for spotting the movements of entire encampments, single vehicles and groups of people. Spy satellites are said by experts to see features as small as 4 or 5 inches across. They can identify people, but not faces. They can spot a license plate on a car, but they can't read it.

Or can they?

Though highly classified, one type of spy satellite known as "Keyhole-class" is thought to see objects as small as a newspaper headline. Experts say three of these satellites, made by Lockheed Martin and costing a billion dollars or more, range over Earth's polar region. They resemble giant digital cameras, somewhat like the Hubble Space Telescope.

Military analysts say Keyhole satellites use an elliptical orbit to take them as close as 200 miles and as far as 600 miles from the planet's surface. This odd orbit allows the satellites, as a group, to photograph nearly the entire planet several times a day, experts say.

Close-up views

To get a closer look, such as in the search for Osama bin Laden, the military employs aircraft. U2 spy planes soar to 70,000 feet and unpiloted drones slip quietly overhead at lower altitudes. The low cost of the drones makes them nearly disposable. These are the tools most experts say are required to tell the difference between a group of refugees and a group of terrorists.

Not all "spy" imaging is done by the military.

The private company Space Imaging uses its Ikonos satellite to snap pictures from 423 miles above Earth, revealing features as small as 3.3 feet across. The company provided images of lower Manhattan after the Sept. 11 attacks on the World Trade Center. And NASA, of course, routinely photographs Earth in the name of science.

No one knows exactly how many satellites the U.S. Military has in orbit. John Pike, director of GlobalSecurity.org, which advises the American intelligence community on post-Cold War security issues, estimates the total number of orbiting spacecraft that support military activity directly or indirectly approaches 100. Included, Pike figures, are roughly two dozen devoted to intelligence, two dozen that provide navigation, and another two dozen that handle communications.

And how effective are they when fighting elusive small groups in rugged mountain terrain?

"What we can do is fairly quickly and fairly precisely locate vehicles and structures in Afghanistan," Pike said. "What we cannot do is track individual people." He added, however, that along with other intelligence information, satellites enable special operations units to locate terrorists, plan forays into enemy territory, and then go in knowing what weapons have been disabled.

Lessons from Desert Storm

Space-based battle support was tested in the Gulf War in 1991. Satellite imagery was used to find targets and assess the effects of bombing. Missile-warning sensors detected enemy Scud launches, information that was relayed -- often by satellite -- to commanders on the ground who controlled anti-missile batteries.

"Desert Storm is considered by many to be the first true test of space systems in support of combat," says Eberhart, the SPACECOM commander in chief. "We used space-based weather and navigation support extensively in the Persian Gulf War, and we still do today."

On Sunday, as the U.S.-led attacks on Afghanistan began, Eberhart said the intelligence data coming from space is better than ever. "The capabilities we provide in terms of intelligence, surveillance, reconnaissance and global communication are very important in the on-going operation Enduring Freedom," he said.

Last Friday, the National Reconnaissance Office added to that fact by launching the second in a trio of new spy satellites that experts say should help in the war against terrorism.

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