Industry perspective: Next-gen PNT needs careful assessment

With the first GPS Block III satellite SVN 74 being set as healthy and active in January, GPS has reached another important milestone. Setting the vehicle healthy and active makes the satellite available for use by military and civilian GPS users around the world. GPS has been a hugely successful system, consistently exceeding its performance specification and providing users with levels of accuracy and availability that would have seemed astonishing only a few short years ago.

Despite these successes, the limitations of GPS and other GNSS have been highlighted by a catalog of real-world well-documented jamming and spoofing incidents, some of which have had serious impacts. With this increase of incidents, the military and commercial worlds have become increasingly aware of the vulnerabilities of sole reliance on GNSS. Interference with GNSS is a critical risk to not only business continuity, but to the safety of the world.

Image: Spirent Federal

Simply trusting the output from a GNSS receiver without question is no longer acceptable in safety- or liability-critical applications. The focus of many manufacturers and developers has been on assuring the integrity of reported GNSS PNT data.

Recently, more systems have begun using non-GNSS data sources to augment the GNSS solution. A GNSS receiver becomes one of the many sensors used in a system that combines their inputs to provide an assured, trustworthy source of precise positioning and timing data even when GNSS is disrupted. There are also active global initiatives in both commercial and military domains worldwide to seek and develop direct replacements for GNSS-based navigation and timing systems.These systems eliminate the use of GNSS completely and are termed “alternative navigation systems.”

Whether assured, augmented or alternative, these PNT systems need careful assessment. Their performance, robustness and resilience need to be measured in normal conditions and with interference.

Spirent is actively working to develop new, relevant test frameworks and designing the next generation of PNT test equipment that can easily integrate with and assess more than one technology. From inertial integrated with GPS to a number of alternative PNT systems that are being analyzed by the U.S. government, Spirent is working to unlock the maximum benefits of the next generation of PNT solutions.

Roger Hart, director of engineering, joined Spirent Federal in 2015. He has worked in development of spacecraft navigation systems, including GPS, for civil, NASA and defense applications since 1986. Guy Buesnel is Spirent’s specialist PNT Security Technologist covering the areas of PNT threats and mitigation.