By May 31, 2016September 3rd, 2018Army ALT Magazine, Science and Technology
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Pseudolites help pave the Army’s path to assured positioning, navigation and timing, providing a ‘protective bubble’ for Soldiers when satellite signals are degraded or denied.

by Maj. Troy Houston

If your personal GPS is wrong, the consequences can be maddening. If a Soldier’s GPS is wrong, the consequences can be disastrous. GPS has become so integral to daily life, and to military operations, that it’s easy to take for granted. But when GPS satellite signals are impeded or denied in a combat environment—by terrain conditions or enemy actions—it affects units’ ability to maintain initiative, coordinate movements, target fires and communicate on-the-move.

As the threat environment changes and adversaries become more sophisticated in attacking existing GPS capabilities, Army senior leaders have stressed the need to achieve assured positioning, navigation and timing (PNT) information by other means. With more than 200 different Army systems that require PNT data, the Army is DOD’s largest user of PNT.

So what does it mean to have assured PNT, and how can the Army Acquisition Corps deliver the capability quickly and affordably to the battlefield? The Pseudolite program—short for “pseudo-satellite”—provides a glimpse.

Mulitsystem Support

An M777 howitzer crew assigned to the 2nd Battalion of the 17th Field Artillery Regiment, 2nd Stryker Brigade Combat Team, 2nd Infantry Division (2-2 SBCT) loads a 155 mm round in preparation for firing during the unit’s Division Artillery Readiness Test in October 2015 at Yakima Training Center, Washington. PNT data is used in Army systems as diverse as the M777, Stryker, Nett Warrior and Rifleman Radio, requiring an enterprise approach to assured PNT. (U.S. Army photo by CPT Meredith Mathis, 2-2 SBCT)


Having accurate PNT information is mission-critical in all environments, but it becomes especially important in environments where adversaries are using anti-access and area-denial (A2AD) capabilities to try to deny our forces freedom of movement and freedom of action.

To deliver data that Soldiers can trust even amid these challenges, assured PNT (A-PNT) has two components:

  • Integrity: the right signal.
  • Assurance: a trusted connection to accurate PNT information.

Integrity describes the reliability of the PNT information received on a GPS device. It answers the questions: Does the signal contain the data the receiver expects? Does the signal come from an authorized and trusted source?

Assurance, meanwhile, measures the accuracy of the PNT information received on a GPS device. It answers the questions: Does the GPS receiver provide an accurate PNT solution? Does the GPS receiver have an active link to a PNT source?

Together, integrity and assurance of the GPS signal minimize operational risk and collateral damage, and maximize the probability of mission success.

The Army is seeking to provide this capability through the A-PNT program, which senior leaders describe as a major priority and critical enabler for the U.S. Army Operating Concept, “Win in a Complex World.” A-PNT comprises four subprograms—Pseudolites, Mounted PNT, Dismounted PNT and Anti-Jam Antennas—that will work together to augment GPS and provide PNT information that Soldiers can trust.


The A-PNT program of record is in its early stages, with the Army science and technology community transitioning solutions and requirements being developed. The most advanced of the subprograms to date is Pseudolites—pseudo-satellites that can pinch-hit for the GPS satellite constellation when needed for operations at brigade-and-below.

Deployed on both unmanned aerial vehicles and ground vehicle platforms, pseudolite transmitters in effect “pull down” the GPS satellite constellation closer to the ground—delivering users a high-power signal that’s more difficult to exploit or deny in A2AD or geographically difficult environments. By leveraging advances in commercial technology and by taking an accelerated, competitive acquisition approach, the Pseudolite program is progressing on schedule through the milestone process in pursuit of its ultimate goal: provide PNT information independent from GPS.

Ready to Receive

U.S. Army Reserve combat engineers from the 374th Engineer Company (Sapper) program their grid coordinates using a Defense Advanced GPS receiver, on a team-based land navigation course in August 2015 during the Sapper Stakes competition at Fort Chaffee, Arkansas. The Pseudolite program is a response to the vulnerability of GPS as the threat environment changes and adversaries become more sophisticated in attacking existing GPS capabilities. (U.S. Army photo by MSG Michel Sauret, 200th Military Police Command)

As a component of the A-PNT architecture in the brigade combat team (BCT), pseudolites augment GPS by providing PNT data to users within a protected area. Using terrestrial- or near-terrestrial-based transmitters as an alternative source of GPS-like signals, pseudolites create a sort of protective bubble for the BCT. The bubble activates when access to the GPS satellite signal is degraded by either friendly or enemy electronic transmission or by natural obstacles such as canyons, urban areas or heavy foliage.

Pseudolites consist of an Anti-Jam Antenna System (AJAS), non-GPS augmentation, GPS receiver, transmitter, and a command and control application. Each pseudolite will use the AJAS to maintain connection to the GPS constellation for as long as possible. Non-GPS augmentation will then step in to provide additional information to the final PNT solution. The pseudolite transceiver will receive and process command, configuration and synchronization data from existing computing and communications equipment within the BCT, and rebroadcast a high-powered GPS-like signal that is recognized and processed by the military GPS receivers within the area of operations.

The planned implementation for pseudolites is at the BCT level, enabling a sufficient level of command and control as well as the ability to react rapidly to changes in the operational environment. To enable A-PNT coverage for the BCT, pseudolites will be integrated onto select ground and aerial platforms within the unit that offer the proximity and availability to provide direct support to maneuver battalion operations. Pseudolites will be fielded as modular, lightweight, self-contained systems compatible for use with aerial platforms, fixed or semifixed structures, antenna masts, towers or aerostats available to the BCT.

The big picture

Pseudolites are to be fielded at the BCT level—as shown here using an infantry BCT (IBCT) as an example—allowing for sufficient command and control as well as enabling rapid response to changes in the operational environment. (SOURCE: PM PNT)

Given the prevalence of GPS in today’s formations, these systems will not be fielded in a vacuum, but instead as part of a “tool kit” that leverages current equipment for maximum effectiveness. Users will control pseudolites through application software on existing network and spectrum management tools within the BCT. Current Military GPS User Equipment (MGUE) devices will receive updates allowing them to use pseudolites as a PNT source, while future MGUE devices will be designed to receive and process the pseudolite signal. As the Army phases in the capability, the pseudolite signal will not cause any harmful effects to user equipment that has not been or cannot be updated.

To further streamline their integration into the force, pseudolites employ an open systems architecture design, aligned with the Sensor Computing Environment baseline as part of the Army’s Common Operating Environment. This modular approach provides the flexibility to integrate various software, hardware and human components designed to satisfy A-PNT. Over time, it will allow the Army to implement software upgrades and modifications to enhance A-PNT, enabling continuous innovation and evolution while minimizing the impact to existing equipment.


With PNT data used in Army systems as diverse as the Stryker, Nett Warrior, Rifleman Radio and the M777 howitzer, A-PNT is a capability that crosses multiple acquisition portfolios. As its different components are developed and fielded, almost every program executive office (PEO) in the Army will have at least one project manager in need of A-PNT.

Formally recognizing the criticality of A-PNT and the need for coordination across and beyond the Army, the assistant secretary of the Army for acquisition, logistics and technology (ASA(ALT)) recently streamlined the A-PNT acquisition process by designating the PNT program office as a direct reporting program manager to the ASA(ALT). This designation enables a faster decision cycle, resulting in the delivery of enhanced capabilities to the Soldier in a compressed timeline.

Managing the program through ASA(ALT) allows the Army to address broader projects and initiatives, such as the Army PNT System of Systems Architecture, that will enable an enterprise approach to assured PNT and prevent an uncoordinated approach by programs with redundant solutions. The structure also enables Program Manager (PM) PNT to plan for the cross-PEO integration efforts required to outpace threats and increase efficiencies in PNT implementation.

Against this backdrop, pseudolites were the first of the family of A-PNT systems to receive a milestone (MS) decision. In May 2015, the subprogram received an MS A decision to enter into the technology maturation and risk reduction phase. PM PNT is now leveraging industry expertise in GPS and GPS alternatives through competitive prototyping. Each company is charged with delivering pseudolite prototypes and laboratory testing. This lab testing will provide the government with data to assess the capability of the prototypes up to Technology Readiness Level 6 in preparation for an MS B review.

Ready to Receive

A Soldier from the 3rd Combat Aviation Brigade (CAB) installs radio communication equipment as the sun sets over Fort Stewart, Georgia, in January. More than 200 different Army systems require PNT data, making the A-PNT program a major priority and critical enabler for the U.S. Army Operating Concept, “Win in a Complex World.” Pseudolites are the most advanced of the four A-PNT subprograms. (Photo by SPC Scott Lindblom, 3rd CAB Public Affairs)


While we think of GPS as the gold standard, it is simply one materiel solution to deliver PNT. As the technology and threat landscape continue to shift, the A-PNT program is breaking ground with several alternative means to provide trusted PNT data to Soldiers.

As the first A-PNT element “out of the gate,” the Pseudolite program is using an accelerated acquisition approach to deliver modular, scalable technology that is flexible to BCT commanders’ needs, integrates with current equipment and can smoothly incorporate future evolutions in antennas, receivers and other technology. Each step in the process takes us closer to the ultimate vision for a pseudolite: a Soldier can turn it on, and the pseudolite will be able to determine its PNT anywhere in the world, without the aid of the GPS constellation, and be totally transparent to the user.

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MAJ TROY HOUSTON is the assistant product manager for pseudolites, part of the Army’s A-PNT program. He holds an MBA and a B.S. in finance from Illinois State University. He is Level II certified in program management.

This article was originally published in the April – June 2016 issue of Army AL&T magazine.

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