GPS World, February 2017

Inertial Ranging eLoran Wi Fi Bluetooth DARPA Advances on Many Alt Fronts T he U S Defense Advanced Research Projects Agency DARPA has initiatives underway with a dizzying number of technologies all seeking to reduce reliance on GNSS in challenged environments Using cold atom interferometry and other techniques to reduce the size weight and power consumption SWAP as well as cost of inertial sensors employing other signals of opportunity SOI chip scale atomic clocks CSAC micro electro mechanical systems MEMS and more the Micro Technology Office MTO and the Adaptable Navigation Systems ANS projects press relentlessly forward to provide U S forces with PNT everywhere and always DARPAs ANS initiative explores tools to enable use of the many sensors available to warfighters and first reponders Over the past two decades the field of robotics has done a lot for extracting features out of imagery and tracking those features as the robot moves through a given environment said Lin Haas says program manger at the Strategic Technology Office Weve been building upon those capabilities and using the capabilities for the purposes of navigation ANS seeks to provide GPS quality PNT to military users regardless of the operational environment It addresses three basic challenges through its Precision Inertial Navigation Systems PINS and All Source Positioning and Navigation ASPN efforts better inertial measurement units IMUs that require fewer external position fixes alternate sources to GPS for those external position fixes new algorithms and architectures for rapidly reconfiguring a navigation system with new and nontraditional sensors for a particular mission PINS is developing an inertial measurement unit IMU that uses cold atom interferometry for high precision navigation without dependence on external fixes for long periods of time Atom interferometry involves measuring the relative acceleration and rotation of a cloud of atoms within a sensor case with potentially far greater accuracy than todays state of the art IMUs 14 GPS WORLD WWW GPSWORLD COM FEBRUARY 2017 A company called AOSense has applied cold atom interferometry to IMUs and demonstrated sensors that support system drifts of 5 meters per hour by using quantum physical properties to measure the relative acceleration and rotation of a cloud of laser cooled atoms The next challenge is shrinking the lasers to microsystem size because the concept requires three lasers generating five beams to cool and move the atoms through interferometers to determine movement and rotation of the device Because even long duration IMUs require an eventual position fix the ASPN effort is developing sensors that use signals of opportunity non navigation signals from sources like television radio and cell towers and satellites as well as natural phenomena such as lightning Our navigation systems tend to be finely tuned and as a result they are fairly brittle in terms of accepting new sensors without a lot of hands on time to make it work said Haas Flexible Combinations Integrating and tuning these diverse sensors maps and other components into a navigation system is expensive and slow producing platform and mission specific solutions The ASPN effort is also developing new fusion algorithms and plug and play processing architectures for rapid integration and nearreal time reconfiguration or upgrading of sensors IMU devices maps and databases on a navigation system With flexible combinations of existing and new navigation sensors INERTIAL SOI MEMS CSAC MORE Micro Technology for Positioning Navigation and Timing towards PNT everywhere and always slide from a 2014 DARPA presentation to the Space Based Positioning Navigation and Timing National Advisory Board Image Robert Lutwak DARPA Micro Technology Office Continued on page 16