WASHINGTON — GPS navigation: Can’t live without it, can’t trust it.
That’s the problem facing military planners as they try to sort through the increasing reliance of equipment and troops on positioning data from satellite networks at a time when the vulnerabilities of GPS are becoming more apparent.
This month, a group of hackers managed to break into ship-tracking software to spell out the word “pwned,” hacker speak for a successful conquest. And over the summer, a group of students at the University of Texas figured out how to send ships off course using fake GPS signals.
That doesn’t mean the US military isn’t working to strengthen the encryption on GPS equipment, which was never designed with security as a top priority. But Pentagon research and development chief Al Shaffer listed GPS security as one of his top concerns.
“It’s becoming easier and easier with modern electronics to do things like jam GPS signals,” he said. “Our military is reliant on GPS both for precision navigation and for time, and most of our weapon systems need very precise time.”
Shaffer mentioned work on inertial measurement units (IMUs) as a possible solution. It’s not a new technology, having been the subject of major research before the invention of GPS, but it’s getting a close look.
The idea is that a unit uses three gyroscopes and three accelerometers to gauge direction and changes in velocity. If given an initial starting point, the mechanisms can be used to provide relative movement data and tell where something has gone.
In 2009, Andrei Shkel started looking into the improved use of IMUs for the US Defense Advanced Research Projects Agency (DARPA), where he worked as a program manager on the microtechnology for the positioning, navigation and timing program.
He started focusing on one of the most demanding problems: IMUs for missiles. The challenge is that the units have to be both small and cost effective, given that they’re set to be destroyed.
IMUs were already in use, but were capable of maintaining accurate location data for only about 20 seconds, meant as a backup measure for the temporary loss of a GPS signal.
Shkel wanted to see if a unit could maintain accuracy for the duration of a missile flight. His research found that 70 percent of missiles flew for three minutes or less, with 98 percent flying for 20 minutes or less.
“The conclusion was that we have very precise inertial instruments that would be able to solve this problem probably 100 percent, but at a very high cost,” he said. “You can’t put a million-dollar inertial measurement unit on a missile that’s under a million dollars.”
Not only were the units expensive, but also quite large.
“The state-of-the-art, low-cost devices were the size of an apple,” Shkel said. “We said, ‘Can we build devices that will solve the problem, but will have the size of an apple seed?’ ”
They largely succeeded. Using semiconductor technology, Shkel and his team came up with a system that could provide three minutes of accurate data that was a fraction of the size of a penny with an anticipated cost of less than $1,000 per unit to manufacture.
