Vehicle Electronics & Architecture (VEA)

Enabling PNT Assurance at all Threat Levels

by Aaron Mebust


Global Positioning System (GPS) technology has become absolutely indispensable to today’s warfighter. GPS signals provide Positioning, Navigation, and Timing (PNT) data that are needed by virtually every critical military system. Digital radio networks require precise time to operate. Direct and indirect fires systems need precise coordinates to accurately determine firing data. Individual soldiers and vehicles need positioning and navigation data to coordinate offensive and defensive maneuver. Battle management systems require the location of every friendly unit in order to provide commanders with an understanding of the battlefield. The list goes on and on. In short, PNT has become a critical element in the ability to shoot, move, and communicate. The dependency on PNT is well understood. The Secretary of the Army recently testified to Congress, “Having accurate PNT information is fundamental to our forces’ ability to maintain initiative, coordinate movements, target fires and communicate on the move.” (Coggins, 2016) The most common source of PNT data is GPS. GPS is extremely cost effective, supporting unlimited users through its space based radio broadcasts. And, until recently, GPS has been universally available and has been a very reliable source of PNT. However, recent events have shown several world powers are in the process of re-invented land warfare. Certain state actors have revealing an advanced ability to disrupt precision navigation and timing capabilities (Australian Strategic Policy Institute, 2016). Our adversaries have increased their levels of sophistication and have attacked existing GPS capabilities with notable skill (Defense One, 2016). Global threats have questioned whether systems relying on PNT will work as expected on the modern battlefield. As Lt. Gen. H.R. McMaster shared in a recent brief, should the U.S. forces find themselves in a land war with Russia, they would be in for a rude, cold awakening (Defense One, 2016). It is clear that an uninterruptable and reliable source of PNT is essential to the warfighter. It is also clear that solely relying on GPS is not a viable course of action for long term sustainability. Although GPS can be encrypted and the upcoming M-Code signals will be stronger, the inherent vulnerability of a weak, space based, sole source solution remains. Independent sources of PNT must be used for validation of GPS and generation of PNT when GPS is unavailable or untrusted. This capability, known as PNT Assurance provides an uninterrupted flow of reliable Positioning, Navigation, and Timing data. Today’s warfighter needs PNT Assurance. Given our reliance on PNT and the vulnerability of GPS, PNT Assurance is not an option, it is a requirement. Having said this, developing a PNT Assurance capability is much easier said than done. Formidable challenges present themselves in developing a solution that will detect threats to GPS, create accurate PNT in the absence of GPS, and then distribute valid PNT to all clients. Once the system is developed, fielding the solution will see challenges regarding integration into existing vehicle architectures along with the requirement to support legacy and future PNT clients. It will not be feasible to require replacement of every Command, Control, Communications, Computers, Intelligence, Surveillance, Reconnaissance and Electronic Warfare (C4ISR/EW) system in a modern vehicle to field a PNT Assurance capability. Finally, Enabling PNT Assurance at all Threat Levels Page 2 ever present budget pressure will require a PNT Assurance solution that is cost effective, scalable, and upgradable. An expensive or “one size fits all” solution is not realistic. When will this critically needed capability be available? Is it possible to move forward with existing vehicle architecture without waiting for new distribution methods (i.e., Ethernet VICTORY)? Can the U.S. and its NATO allies use currently available Commercial Off The Shelf (COTS) items to ensure PNT data accessibility no matter what the threat? Can the U.S. ensure adequate, authenticated PNT data regardless of GPS availability or integrity? Finally, how can cost effective fielding, scalability and sustainment be addressed? This paper will address the challenge of developing a PNT Assurance capability. We will discuss the drivers and benefits using various sensors such as Chip Scale Atomic Clocks (CSAC), Inertial Navigation Systems (INS), and existing vehicle data sources such as a vehicle Controller Area Network (CAN) Bus to implement and field PNT Assurance. It will also discuss migrating to PNT Assurance while living within the constraints imposed by legacy systems that will never be completely updated. It will address the risks that must be mitigated and benefits achieved from a centralized PNT source distributing PNT to each client (a distributed architecture). Finally, this paper shall serve as a baseline recommendation to the ground vehicle community for bridging the gap between legacy systems deployed today and the C4ISR/EW architectures of the future by the distribution of valid PNT data across all formats (coaxial, wireless, serial data, Ethernet). The conclusion supported shall be that a cost-effective strategy can be adopted by a joint industry/Government team for the implementation of PNT Assurance within an existing non-VICTORY architecture and that this solution shall support future VICTORY enabled architecture. The baseline PNT Assurance capability shall also serve as a proof of concept and a development platform for future developments in PNT resiliency.