By Alan Cameron
Call it irony, poetic justice, or just the nature of the beast. The same impulse that led to the invention of GPS now has engendered a drive to beget non-GPS.
In the 1970s, the U.S. military began putting together a program “to drop five bombs in the same hole.” The program office, to the wall of which that mission statement was tacked, went on to develop the first satellite navigation positioning system: GPS. In 2012, the U.S. Defense Advanced Research Projects Agency (DARPA) declared that this system no longer sufficed for reliable delivery of precision munitions under every circumstance.
“More than 98 percent of the missiles currently in the U.S. arsenal have mission durations of less than 20 minutes, and today, almost all of these missions are critically dependent on GPS for achieving the required level of delivery accuracy,” a communiqué stated.
Because of vulnerability to jamming, spoofing, and other intentional or unintentional modifications of position, orientation, and time information, the agency has put forth a new goal “to completely eliminate dependence on GPS or any other external signals during the mission and rely solely on self-contained solutions such as inertial navigation,” which is immune to such extrinsic actors.
The Chip-Scale Combinatorial Atomic Navigator program has made 10 exploratory grants to investigate and develop this concept, to large corporations, a small start-up, national labs, and academic groups. Only one has been announced, by contracting agent Wright Patterson Air Force Base, to AOSense. DARPA wishes to emphasize that this is a sample of what is happening in C-SCAN, and should not been viewed by readers as the only technical approach paving the way.
The company, located in Sunnyvale, California, has gotten busy building an experimental navigation-system-on-a-chip that combines traditional, solid-state, and atomic inertial guidance technology. Their goal: create a sensor on a chip that works reliably, without drift, over considerable distances for at least 20 minutes.
AOSense is exploring how to shrink and fabricate atomic sensors together with high-performance solid-state inertial sensors. DARPA hopes the C-SCAN program will lead to a breed of inertial microsystems, with a wider range of operating conditions and greater immunity to the environment, reduced start-up time, increased sensitivity, and improved bias and scale factor stability. Oh, and not cost too awful much per piece.
Another project at Northrop Grumman seeks to develop a micro-gyro for personal and unmanned vehicle navigation.
Despite impressive micro-PNT work to date, current mechanisms remain complex, bulky, power-hungry — and pricey. They have limited resolution and poor long-term stability. Alternative forms give excellent resolution and bias stability, but are limited in bandwidth and generally do not allow high-frequency measurements.
Make no mistake, however. Yankee (and whatever other forms that can be brought to bear) ingenuity will, eventually, win the day. Where then will GNSS find itself?