New DARPA Technologies: Beyond GPS

DARPA researchers at the University of Michigan report that they have made significant progress with a timing and inertial measurement unit (TIMU) that contains everything needed to aid navigation when GPS is temporarily unavailable. The single-chip TIMU prototype contains a six-axis IMU (three gyroscopes and three accelerometers) and integrates a highly-accurate master clock into a single miniature system, smaller than the size of a penny. This chip integrates devices (clocks, gyroscopes and accelerometers), materials and designs from DARPA’s Micro-Technology for Positioning, Navigation and Timing (Micro-PNT) program.

As reported by Information Week: When it comes to military operations, GPS is not always a reliable technology for positioning, navigation, and timing (PNT). Yet PNT capabilities are essential to targeting missiles; navigation for land, sea, and air forces; and precision in military operations overall. That's why the Defense Advanced Research Projects Agency (DARPA) has created several programs to develop other approaches that offer more dependable and accurate PNT capabilities when GPS isn't working properly.

"We are putting new physics, new devices, and new algorithms on the job so our people and our systems can break free of their reliance on GPS," DARPA director Arati Prabhakar said in a statement.

The restricted nature of GPS is due to environmental factors such as solar storms, when signals are degraded, and is especially apparent to war-fighters underground and underwater. GPS transmit levels from orbiting satellites are extremely low power and are therefore weakened by the time they reach Earth. The signals can also be obstructed by dense trees or buildings. They also cannot penetrate water, which makes GPS problematic for various military applications.

"More worrisome is that adversaries can jam signals. GPS continues to be vital, but its limitations in some environments could make it an Achilles' heel if war-fighters rely on it as their sole source of PNT information," DARPA says on its program website. In fact, illegal devices that jam GPS signals are becoming increasingly available. Some simple gadgets that plug into 12-volt car receptacle connectors and cost as little as $30 can render GPS systems inoperable for miles, according to GPS systems provider NovAtel.

In its search for new technologies that offer an alternative to GPS, DARPA is particularly interested in systems that provide long-duration precision and accuracy in positioning and timing for global synchronization, secure communications, and cooperative effects. Such technologies include architectures for ad-hoc PNT networks, sensors, and signal processing designed to perform in adverse environments, and new architectures that enable communications, electronic warfare (EW), and intelligence, surveillance, and reconnaissance (ISR) systems to support PNT systems.

The agency needs affordable, compact, and flexible systems that can be used for a broad range of defense missions. For example, DARPA issued a solicitation in June seeking proposals for PNT systems that can operate independent of GPS, as part of its Spatial, Temporal, and Orientation Information in Contested Environments (STOIC) program.  

Microtechnology for positioning, navigation, and timing (Micro-PNT) enables extreme miniaturization using micro-electromechanical systems (MEMS) technology. DARPA researchers have built a prototype that contains three gyroscopes, three accelerometers, and a master clock on a chip -- small enough to fit on a penny. These self-calibrating, high-performance microscale sensors are not only affordable, but they also offer size, weight, and power (SWAP) improvements over currently available sensors.

DARPA's Program in Ultrafast Laser Science and Engineering (PULSE) is using pulsed laser technology to improve atomic clocks and microwave sources, including their size and precision. For example, PULSE enables more accurate time and frequency synchronization over long distances. According to DARPA, PULSE technology is necessary for super-accurate atomic clocks, such as the world's most accurate optical atomic clocks.

DARPA is developing adaptable navigation systems (ANS), which entail new algorithms and architectures for plug-and-play integration of PNT sensors across multiple platforms. ANS uses cold-atom interferometry, which "measures the relative acceleration and rotation of a cloud of atoms stored within a sensor," according to DARPA's website. The agency's vision is to cut development costs and deployment time from months to days, and use quantum physics to build accurate inertial measurement devices that can operate longer without requiring external data to determine time and position. Additionally, ANS is exploiting non-navigational electromagnetic signals, such as lightning strikes, to provide stronger signals than GPS.

Quantum-assisted sensing and readout (QuASAR) has the ability to take atomic clocks out of labs and make them both robust and portable. This could result in new radar, metrology, and light detection and ranging (LIDAR) applications. DARPA's QuASAR program builds on atomic physics to develop a set of measurement tools that will be applicable across disciplines. The Defense Department specifically would have access to various types of devices that include imaging, inertial navigation, and robust global positioning systems.

DARPA's Spatial, Temporal, and Orientation Information in Contested Environments (STOIC) program focuses on developing systems that provide non-GPS positioning, navigation, and timing with GPS-level timing. STOIC encompasses three primary elements that have the potential to provide PNT independent of GPS: long-range robust reference signals, ultra-stable tactical clocks, and multifunctional systems that deliver PNT information among multiples users. When complete, STOIC will offer better PNT in challenging environments where GPS isn't working properly or is unavailable.