BEYOND GPS
DATA SOLDIERS CAN TRUST Having accurate PNT information is mission-critical in all environments, but it becomes especially important in envi- ronments where adversaries are using anti-access and area-denial (A2AD) capabilities to try to deny our forces free- dom 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 accu- racy 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.
Te 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 informa- tion that Soldiers can trust.
THE PSEUDOLITE SOLUTION Te A-PNT program of record is in its early stages, with the Army science and technology community transitioning solu- tions and requirements being developed. Te most advanced of the subprograms to date is Pseudolites—pseudo-satellites that can pinch-hit for the GPS satellite con- stellation when needed for operations at brigade-and-below.
A BETTER PATH TO A-PNT U.S. Army Reserve combat engineers from the 374th Engineer Company (Sapper) program their grid coordinates using a Defense Ad- vanced 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 re- sponse 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)
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 geographi- cally difficult environments. By leveraging advances in commercial technology and by taking an accelerated,
competitive 54
acquisition approach, the Pseudolite pro- gram is progressing on schedule through the milestone process in pursuit of its ultimate goal: provide PNT information independent from GPS.
As a component of the A-PNT architec- ture 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. Te 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 aug- mentation, 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 augmenta- tion will then step in to provide additional information to the final PNT solution. Te pseudolite transceiver will
and process command, configuration and synchronization data from existing com- puting and communications equipment within the BCT, and rebroadcast a high- powered GPS-like signal that is recognized and processed by the military GPS receiv- ers within the area of operations.
Te planned implementation for pseu- dolites 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 environ- ment. 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
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Army AL&T Magazine
April-June 2016
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