Will GPS Wear Itself Out?

Will GPS Wear Itself Out? asks William Matthews and reports that experts say already the system will be less reliable if older satellites fail. Four F/A-18 Super Hornets hurtled off the deck of the aircraft carrier USS Dwight D. Eisenhower in the Arabian Sea and sped north toward Afghanistan on April 26 to drop 500-pound GPS-guided bombs on dug-in Taliban machine gunners.

Thanks to GPS, the bombs hit their mark, ending a firefight on favorable terms for U.S. forces on the ground, Air Force Lt. Gen. Larry James told a U.S. House subcommittee.

"GPS provides critical services every second to our deployed forces around the globe," James said, "from the infantrymen walking the streets of Fallujah, to the ships combating piracy off the coast of Somalia, to the aircraft patrolling our country's borders."
James commands the 14th Air Force and the Joint Functional Component Command for Space. GPS - the Global Positioning System - is his baby.

But there's a problem threatening GPS. Its 30 satellites are wearing out, and new satellites being built to replace them are three years behind schedule and have more than doubled in cost, from $729 million to $1.6 billion.

Sometime in 2010, "as old satellites begin to fail," it is possible that the GPS network will be unable to provide the level of accuracy that the U.S. military needs, Christina Chaplain of the Government Accountability Office told the House Oversight and Government Reform Committee's national security subcommittee May 7.
If that happens, GPS-guided bombs may miss their targets, troops in distress may be harder to rescue, navigation may become less certain, and telling friend from foe on the battlefield may become harder.

And it's not just a problem for the military.

"It is not an exaggeration to say that GPS is everywhere," said Michael Swiek, director of the United States GPS Industry Council.
"Whenever you make a call on your cell phone, withdraw money from your ATM or send an e-mail, you are using GPS," he said.
Airlines rely on GPS to plan routes that save fuel; banks rely on precise GPS time signals to authenticate electronic transactions; GPS synchronizes communications and aids in activities from weather forecasting to earthquake predicting. GPS-based systems in automobiles alert police to car crashes and medical emergencies.
GPS probably won't disappear, but there are likely to be gaps in GPS service.

GPS needs at least 24 working satellites to provide signals that maintain the level of service that's available today. But starting next year, "the probability of maintaining a constellation of at least 24 operational satellites falls below 95 percent," Chaplain said. And between 2010 and 2014, the probability falls to as low as 80 percent.
If replacement GPS satellites are delayed for an additional two years, there is a 90 percent chance that the Air Force won't have 24 working GPS satellites, Chaplain said.

The first new GPS satellite originally was to be launched in 2006. Now it's scheduled for launch in November, but it suffers from "significant technical problems that still threaten its delivery schedule," Chaplain said.

James said the Air Force might be able to prevent GPS service from degrading by using "partially mission-capable satellites" as backups for any GPS satellites that fail. There are three such satellites available now, he said. And the service might be able to prolong the lives of current GPS satellites by turning off their equipment used for missions other than providing GPS signals, he said.
Building a new generation of GPS satellites has been a struggle for the Air Force, Chaplain said.

The effort began in 1996 and has been plagued by technical troubles and management problems. Mergers among contractors and Air Force requirement changes added to cost overruns and schedule delays, Chaplain said.

Originally, Rockwell won the contract in 1996 to build GPS IIF satellites. Then Rockwell was bought by Boeing. The GPS program was relocated twice as Boeing bought McDonnell Douglas and then Hughes Electronics. With each move, experienced employees were lost and delays were compounded. There have been seven program managers.

There were technical difficulties, too. In 2008, progress ground to a halt while Boeing tracked down the cause of a transmitter failure. Parts became obsolete; there were problems with maintaining proper propellant fuel-line temperatures; there were satellite power failures.

"The problems experienced on the IFF program are not unlike those experienced in other Defense Department space system acquisitions," Chaplain said. "What sets GPS apart from those programs is that GPS has already been done before."
In 2008, Boeing lost a bid to build even more advanced GPS IIIA satellites to Lockheed Martin.

News that GPS soon may become less reliable is likely to be a surprise to many, even those in the military.

"I can't say that [military commanders] are necessarily aware that there is a potential of possible degradation in the future," James told the subcommittee. "Their concern is more near-term - am I getting my GPS signal today?"

Most commercial GPS users are also probably unaware of possible service interruptions, said Swiek of the GPS Industry Council.
"Engineers, technical people, people in the manufacturing community" are aware of the problem, he said. But among "the public at large, the users of GPS, particularly in the consumer area, I would say there the awareness is probably nowhere near as great."

Source: Ecoterra Intl, May 18, 2009

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