Enabling PNT Assurance at all Threat Levels
Authors: Mebust Aaron 
Published: November 2024

<title>ABSTRACT</title>
<p>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.” (<xref rid="R2" ref-type="bibr">Coggins, 2016</xref>)</p>
<p>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 (<xref rid="R1" ref-type="bibr">Australian Strategic Policy Institute,
2016</xref>). Our adversaries have increased their levels of sophistication and
have attacked existing GPS capabilities with notable skill (<xref rid="R4" ref-type="bibr">Defense One, 2016</xref>). 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 (<xref rid="R4" ref-type="bibr">Defense One, 2016</xref>).</p>
<p>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.</p>
<p>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, 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.</p>
<p>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?</p>
<p>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).</p>
<p>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.</p>