PM PNT tests pseudolite characterization and performance

Two Army hummer vehicles are positioned inside the Army Research Laboratory's shielded anechoic chamber located at the White Sands Missile Range, New Mexico. Pseudolite prototype systems were tested within the anechoic chamber to better understand transmission capabilities, navigation abilities, interference thresholds, and overall performance. | U.S. Army photo

WHITE SANDS MISSILE RANGE, NM— The Army remains focused on assured positioning, navigation and timing, known as A-PNT, as it continues to modernize warfighter capabilities and better secure PNT mission-critical environments.

Last month, the Program Manager for Positioning, Navigation and Timing, or PM PNT, held a three-week test of pseudolite characterization and performance— a component of the A-PNT program that transmits signals similar to that of GPS. The test concentrated on pseudolite performance at various jamming, or interference, levels as well as risk reduction elements to prepare for future field tests. Secondary test objectives, to include anti-jam antenna system, or AJAS, and receiver (e.g., military legacy, commercial, and Pseudolite enabled) system performance, were also observed.

An unmanned aerial vehicle is positioned inside the Army Research Laboratory’s shielded anechoic chamber located at the White Sands Missile Range, New Mexico. The chamber is the Army’s largest anechoic chamber providing an ideal work place for applied research, development, test, evaluation, and experimentation. | U.S. Army photo

Understanding The Pseudolite Solution

The pseudolite system consists of an AJAS, non-GPS augmentation components, command and control application, an output signal generator, a high-power transmitter, and a secure military GPS receiver. Described as “pseudo-satellites”, pseudolites are terrestrially-based devices that transmit signals similar to GPS.

By creating a GPS constellation closer to the ground, through the use of aerial and ground based platforms, pseudolite transmitters deliver a high-power signal that is more difficult to manipulate (i.e., jamming) or obstruct (i.e., difficult geographical environments). The increased signal power improves a GPS receiver’s ability to acquire and track PNT information, providing a protected area for the warfighter to operate. Pseudolites is intended to provide direct support to maneuver battalion operations, delivering scalable technology that is flexible to warfighter needs.

Testing The Pseudolite System

The PM PNT A-PNT pseudolite test took place at a facility located at the White Sands Missile Range, New Mexico where a test team evaluated Army weapon system survivability against the full spectrum of threats on and off the battlefield.

Over the course of three weeks, pseudolite prototype systems were observed within a shielded anechoic chamber to better understand transmission capabilities, navigation abilities, interference thresholds, and overall performance. The test team created a GPS constellation similar to that within the earth’s atmosphere, simulating a true-to-life operational environment within the chamber. Tests were timed to account for constellation movement due to the earth’s rotation.

To better understand pseudolite performance and characterization, test scenarios were constructed to assess the pseudolite prototype systems using operationally relevant jamming signals. Jamming signals were increased incrementally and throughout the duration of the test to better understand Pseudolite performance in low-end and high-end interference levels. Additionally, pseudolite broadcast power was increased at an incremental rate from low to full power to measure variance in signal effects.

Secondary observations gave light to AJAS effectiveness and impact, functional influence to legacy military and commercial GPS receivers, and retrieval rates of the pseudolite signal by pseudolite enabled military receivers. The pseudolite signal presents itself differently from GPS and jammer signals, meaning military GPS receivers must have the appropriate software to recognize and accept the pseudolite signal to form a navigation solution.

“I was very excited to see how pseudolites performed in the chamber environment,” said Kevin Coggins, Program Manager for PNT. “What we learn from these tests will impact how the Army develops and implements the pseudolite capability, providing the warfighter with alternative PNT solutions that give them better protection and increased trust.”

The chamber test gave the PM PNT test team a first-time look at the pseudolites constellation— examining performance of each prototype component— as well as pseudolite navigation solution capabilities. Results from the recently completed chamber test will influence future tests scheduled for FY18.

The A-PNT Solution

Pseudolites are only one solution under development within PM PNT. A-PNT will employ a system of systems architecture designed to assure PNT in nearly all GPS challenged environments, across all formations and warfighting functions. Pseudolites will provide area protection by transmitting a GPS-like signal. There are three other components that make up the A-PNT solution, which are intended to complement each other:

  • Dismounted A-PNT: Provides optimization of size, weight, and power of a PNT source, Pseudolites, and non-GPS augmentation to increase access and integrity while distributing PNT to dismounted Warfighter systems.
  • Mounted A-PNT: Provides PNT source utilizing GPS, Pseudolites, and non-GPS augmentation that increases access and integrity while distributing PNT to systems on mounted platforms.
  • AJAS: Provides point protection by focusing on valid signals and eliminating interference signals.

The A-PNT system of systems is designed to work as an integrated capability. The A-PNT program focuses on platform distribution of PNT, scalable PNT architectures that outpace the threat, and the ability to upgrade to future technologies, including Military-Code (M-Code). M-Code is expected to further improve anti-jamming capabilities and secure access to military GPS signals.

Future Tests

PM PNT continues to test system capabilities for the A-PNT program in an effort to deliver innovative PNT technologies that will augment and enhance GPS for the warfighter in the field. PM PNT plans to conduct future Pseudolite testing as part of the A-PNT acquisition strategy.

For more information regarding PM PNT products and programs, visit the PM PNT website at https://www.pmpnt/army.mil/.

By Caitlin O’Neill, PM Position, Navigation and Timing