AF worried that GPS signals might get drowned out

By: TOM ROEDER
March 23, 2011
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The Air Force is worried that a proposed commercial broadband Internet system could make the nation’s Global Positioning System receivers go on the blink.

Virginia-based LightSquared plans to combine a satellite network with thousands of ground transmitters to provide mobile Internet services. Air Force Space Command in Colorado Springs fears those ground transmitters, which operate at a frequency near the one used by its navigation satellites, could drown out GPS signals.

“Can you imagine if we have to change a half billion receivers?” Space Command’s vice-commander, Lt. Gen. Michael Basla asked at a Wednesday luncheon sponsored by the Greater Colorado Springs Chamber of Commerce.

Jeff Carlisle, LightSquared’s vice president for regulatory affairs, said his firm is working with the Air Force to test its transmitters and to figure out ways to avoid interference with GPS receivers. But Carlisle noted that those receivers could be part of the problem because they pick up radio frequencies not assigned to GPS.

A quick lesson: Radio waves fly through the atmosphere like the sound waves from a singer. If two singers are right next to each other belting out different songs, the loudest one wins.

Space Command oversees the nation’s GPS satellites, which are operated from a control station at Schriever Air Force Base on the plains east of Colorado Springs. Those satellites send out relatively weak signals, which Basla compared to a 15-watt light bulb seen from a distance of 3,000 miles.

That’s Basla’s worry. The Internet transmissions would be louder than the GPS signals, making it so GPS receivers can’t get the information they use to navigate. So, essentially, LightSquared could drown out GPS signals.

Basla said if the interference is widespread it would cause “significant consequences to our nation.”

The GPS signal was first used exclusively by the military, but has embedded itself in every sector of the modern world, with hundreds of millions of users.

Most people know about the handy in-car navigation systems the satellites enable. Less known, but more important, is how the timing signal from GPS satellites makes cell phone systems, ATMs and even the Internet itself possible.

Billions have been spent on the satellite system and the Pentagon is midway through a $5.8 billion plan to launch new satellites and improve ground stations.

The Federal Communications Commission, which regulates use of the nation’s radio waves, gave LightSquared the preliminary go-ahead for the system in January, with a final decision due in June. To get full approval, LightSquared must present a plan that addresses GPS interference.

LightSquared sent a team, including Carlisle, to Peterson Air Force base this month to meet with Space Command GPS experts about their concerns. Basla said a testing program set to begin in April will test whether the company’s Internet transmissions cause interference.

There’s big money on the line for LightSquared.

It has spent $1 billion on its satellite system and has plans to spend another $14 billion on ground-based transmitters, Carlisle said.

The company’s plan is to provide Internet services that are available everywhere in America by using the combination of cellular towers and satellite signals.

“It will be like having a high speed data network in your pocket,” Carlisle said.


Call the writer: 636-0240

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