GPS for Denied Environments on the Horizon

September 15, 2010
By Rachel Eisenhower

Dr. Werner Dahm, chief scientist, U.S. Air Force, recently discussed the findings of the Air Force Technology Horizons effort. The four-volume document compiled and released this year focuses on Air Force science and technology efforts in the coming decade and beyond. Volume one of the series is publicly releasable (PDF link).

Each element outlined in the study addresses a trifecta of challenges: strategy, technology and budget. The major findings include the Air Force's push for a broader use of autonomous systems and the development of technologies for greater freedom of operations in Global Positioning System (GPS)-denied environments, says Dahm.

"We know our adversaries are going to try to deny us our GPS capability, because we are so dependent on it," observes Dahm. To confront these challenges, the report focuses on the continued development of chip-scale atomic clock devices along with a variety of advanced inertial measurement and miniaturized units.

The chip-scale atomic clock devices could enable miniaturized and low-frequency systems for high-security, jam-resistant GPS receivers. This would greatly improve the portability of military platforms with navigation requirements. Dahm notes that the miniaturization of these devices to roughly the size of a watch will allow the Air Force to build them into essentially any equipment which will operate for a relatively short time with minimal uncertainties in position and timing.

The real breakthrough, reveals Dahm, will come from the quantum interferometry approaches, often referred to as cold-atom approaches, where scientists trap a collection of atoms or molecules in a very narrow range of quantum states. "We use the fact that at the quantum level matter-in other words, atoms and molecules-are waves," explains Dahm. The wavelength of these waves is many orders of magnitude smaller than optical wavelengths, which allows for incredibly high precision and low drift in position and navigation systems.

Those technologies are at laboratory scale today, but Dahm says they are advancing quickly and could be fielded in the next decade.

If they succeed, the Air Force will have GPS or better-than-GPS position and timing systems even in environments currently lacking the systems' capabilities. "And by doing that, we will, in effect, have negated our potential adversaries' value from their efforts to deny us GPS in the first place," Dahm says.

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So this means that a navigation system can maintain its positioning capability without an update from the satellite for an extended period of time. So does it work like an odometer and it is tied to the movement of the vehicle? What is the external reference points used to track movement?

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