More than half a century after a study by The Aerospace Corporation first laid out the design options for it, the Global Positioning System (GPS) is now used for a vast array of missions, from personal navigation to tracking fleets of vehicles, from landing aircraft to timing the Internet, from location-based services to missile guidance, from surveying to scientific research. This has made GPS – as the essential source of positioning, navigation, and timing (PNT) data – a “critical infrastructure”  for the country. For this reason, the U.S. Air Force, through its Space and Missile Systems Centerís GPS directorate, has been working for many years to modernize, toughen, and augment the system and to increase its resilience against such threats as jamming, spoofing, and space weather events.

Additionally, the Department of Defense is now promoting the development of an alternative PNT system to act as a backup to GPS. As part of this effort, two years ago Aerospace launched Project Sextant, to study current and future options to improve the resilience, flexibility, and availability of PNT where and when GPS is not available. A federally funded research and development center chartered in 1960, during the space race, Aerospace Corporation is “unbiased and free from conflict of interest,” says Dr. Randy Villahermosa, the Executive Director of the companyís Innovation Lab. Its primary mission is to assure the success of U.S. satellite systems and missions.

Project Sextant is studying how to protect PNT services from both natural phenomena and man-made threats, how to increase flexibility and reduce costs, and how to expedite the introduction of new technologies. The study’s scope includes inertial sensors, optical sensors, and “beacons of opportunity,” such as WiFi routers and cell phone towers. All of this work overlaps in large part with the parallel effort by car manufacturers, car service companies, and geospatial hardware and software vendors to develop self-driving cars (Editor’s Note: See “Lidar is Key to Autonomous Vehicles” in the Winter 2017 issue of Apogeo Spatial (). It aims to transition from GPS, which is a vertically integrated system, to a horizontally integrated system in which GPS is augmented by a variety of PNT sources.

According to Villahermosa, one initial conclusion of the study is that there is currently no replacement for GPS. Another one is that end users should have more flexibility in how they integrate different sources of PNT using a single device.

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