- The Washington Times - Wednesday, November 30, 2005

When the Soviet Union launched the Sputnik satellite into orbit in 1957, it dealt a blow to the United States’ collective pride.

The space race was all the rage back then.

Today, satellites are more than just nationalistic symbols. They help bounce communication signals around the globe, let newspapers transmit text to printing presses nationwide and guide travelers via global positioning system gadgetry.

Satellites may seem as if they were born from fires stoked by the Industrial Revolution, but the concept dates back to Sir Isaac Newton, says Ken Wilson, director of astronomy at the Science Museum of Virginia in Richmond.

More than two centuries later, science-fiction writer Arthur C. Clarke wrote an influential 1945 technical paper exploring the principles behind satellite communication.

Satellites serve as space-bound relay stations, bouncing electronic signals to and from the Earth at great speeds.

Today’s satellites, like Sputnik and its immediate successors, revolve around the Earth in a circular or elliptical path, or orbit. The space vehicles break down into three key groups — commercial, military and civilian satellites.

Add them up, and the figures are eye-popping — $91 billion in worldwide revenue in 2003, according to the District-based Satellite Industry Association, a trade association representing various satellite firms.

Mr. Wilson says satellites typically follow a geosynchronous orbit, meaning they stay above the same place on Earth while the planet rotates on its axis. These satellites beam television signals and satellite radio transmissions into our homes. Geosynchronous satellites orbit roughly 23,000 miles above the Earth’s equator and make up the overwhelming majority of total satellites.

Polar-orbiting satellites, in contrast, move over the planet’s poles on every revolution. They typically help provide mapping services.

“The Earth turns underneath it. It can map the entire surface,” Mr. Wilson says, adding that some satellites measure ocean temperatures via infrared sensors.

Perhaps the most renowned satellite currently above the Earth is the Hubble Space Telescope. This satellite reached orbit in 1990 and has been providing researchers with data about the universe ever since.

Not every satellite survives so long.

David Cavossa, the Satellite Industry Association’s executive director, says the newest satellites’ average life span ranges from 15 to 20 years.

“It’s all about fuel on board … fuel equals lifetime,” says Mr. Cavossa, who adds that 1,083 satellites from around the world are in orbit. “Even though [a satellite] is in the vacuum of space, it’s affected by gravity and friction. You have to use a little fuel to push it in the right direction.”

Solar panels keep the average satellite powered up, but the thrusters, which help adjust its proper orbit, require fuel.

The modern satellite, Mr. Cavossa says, is superior to older models mainly because of its ability to use fuel resources more efficiently.

Once a geosynchronous satellite has gobbled up nearly all of its fuel, it is sent to what Mr. Cavossa calls its “graveyard orbit.”

The pathway typically is 200 to 300 kilometers above its former orbit so it won’t interfere with still-functioning satellites.

“It’s the equivalent of sinking a ship,” he says.

Polar-orbiting satellites, which travel more closely to Earth, are de-orbited and brought back into the Earth’s atmosphere to be burned up when their fuel tanks near empty.

Satellites reach their final destination — either a polar or geosynchronous orbit — by hitching a ride on a space-bound rocket or shuttle.

“Both the U.S. and non-U.S. governments launch satellites through their own vehicles and through companies like Boeing,” Mr. Cavossa says. “When an XM or DirectTV want to launch a satellite, they’ll contract Boeing and Lockheed or Orbital, the three U.S. launch providers.”

The Federal Aviation Administration licenses commercial satellite launches, while other countries feature different approaches for approving launches within their borders.

No matter who fires up the rocket, it likely will involve several stages to help the satellite reach high into the sky, says Mike Cauley, project engineer at Cleveland’s NASA Glenn Research Center.

Those stages help the satellite near its eventual orbit, Mr. Cauley says. Then, it’s up to the Apogee Kick Motor, or AKM, to do the rest.

“When it’s in the right position, it will fire that AKM that places it into geosynchronous orbit,” Mr. Cauley says.

Alas, even when the perfect orbit is achieved, the thrusters have more work to do.

“You have to have those motors periodically fire when it drifts out of a pre-defined box,” Mr. Cauley says. “The moon and the sun have gravitational tugs on it.”

Armand Makowski, professor in computer engineering at the University of Maryland at College Park, says some of the latest advances in satellite technology come from the military’s research teams.

“Today you have satellites with sophisticated sensors they didn’t have five years [ago], especially in the [espionage] side of the family,” Mr. Makowski says.

He says the costs involved in satellite maneuvers depend not only on the solar-powered cells but on creating “hardened” materials that can survive in space for more than a decade.

“It’s an extremely conservative business because any time you put a bird up there, it’s $100 million,” Mr. Makowski says.

Imagine the loss, then, if two satellites collided.

Mr. Cavossa says satellite safeguards similar to those in place for air-traffic control systems make sure collisions don’t occur. Both commercial and government satellite operators know the range of space in which their devices orbit, and they keep those devices within that space, he says.

Should an operator lose control of a satellite, a very rare event, he or she will contact satellite officials to alert them to the problem. Plus, the U.S. government tracks all items of significant size in space and sends out warnings whenever a satellite leaves its predetermined course.

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