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American Forces Press Service

Department Seeks to Protect GPS Operations

By Elaine Sanchez
American Forces Press Service

WASHINGTON, Sept. 16, 2011 – Defense Department officials are raising concerns that a company’s proposed wireless broadband network would cause harmful interference to essential Global Positioning System operations.

LightSquared’s new terrestrial network has the potential to wreak havoc on GPS systems that are vital to the military and used in a host of applications, Teresa Takai, the DOD’s chief information officer, and Air Force Gen. William L. Shelton, commander of Air Force Space Command, told members of the House Armed Services Committee’s Subcommittee on Strategic Forces yesterday.

“GPS is vital to national security and is relied upon by our servicemen and women for a wide array of capabilities,” Takai said in written testimony.

GPS is the cornerstone of the Defense Department’s positioning, navigation and timing services, and is integrated into nearly every aspect of the nation’s military operations, she said. GPS signals are used to ensure the accuracy of precision-guided munitions, guide troop movements, synchronize communications networks, enable battle-space situational awareness, and conduct search and rescue missions.

“The ability of GPS to operate without harmful interference remains of paramount importance to the department,” Takai said at the hearing.

The military recently conducted testing on LightSquared’s network in concert with the Federal Aviation Administration, Shelton explained, which involved more than 100 receivers from 24 different organizations, and spanned the military, government, aviation, precision, agriculture, automotive and general-use communities.

Test data indicate that LightSquared’s signals interfered with every type of receiver in the test, the general said. Since that time, he added, the company has proposed an alternate deployment plan that would initially use only the lower 10 megahertz of its assigned frequencies.

However, limited testing on this new proposal still indicates an effect on precision receivers and even some cell phones, Shelton said, adding that further testing would be required to fully characterize potential interference.

“Based on test results and analysis to date, LightSquared’s network would effectively jam vital GPS receivers, and to our knowledge thus far, there are no mitigation options that would be effective in eliminating interference to essential GPS services in the United States,” the general told the subcommittee members.

Takai said the Defense Department also is evaluating the effects of LightSquared’s terrestrial transmissions on the military’s use of Inmarsat satellite systems for its data and voice needs. Inmarsat satellite terminals are used by military units, commanders and other senior government officials for global communications.

“The LightSquared terrestrial system will likely interfere with DOD usage of Inmarsat if appropriate actions are not taken to mitigate interference,” she said.

DOD officials would like to work with the FCC, National Telecommunications and Information Administration, and LightSquared to ensure any proposed network alternatives are thoroughly tested to prevent harmful interference to GPS receivers or other military spectrum requirements, Takai said.

Along with the military, GPS is vital worldwide in a wide range of applications, Shelton noted. While GPS is a military-procured and operated satellite constellation, he explained, it’s also recognized as a global utility used by people around the world.

In fact, GPS use is so ubiquitous in the United States, Shelton said he’d put it in the category of critical infrastructure.

GPS is used within the aviation community and by the Homeland Security Department for national border and maritime security, he said. And first responders, such as law enforcement, medical emergency and firefighting crews, depend on GPS to respond quickly to time-urgent events.

“As a nation, we have invested roughly $34 billion to field and operate the GPS constellation,” Shelton said in his written remarks to the subcommittee. “Clearly it has become a global utility serving a worldwide user population.”

Committed to sustaining and improving GPS, officials have scheduled several innovations over the next 10-plus years, Takai said, including three new civil signals, enhanced encrypted military signals, and a new constellation operational control segment, which are scheduled to come online by 2018 and be implemented systemwide over the next five years.

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