GNSS is the only global, free, comprehensive technology providing absolute PNT data to users worldwide. Its limitations are known, including long life cycle and replenishment schedule, affecting their ability to adapt easily to short-term market needs and to some extent, resilience.

Considering the above, alternative PNT methods and solutions have been developed or are being investigated, innovative PNT systems are emerging (ground-based or space-based). These systems are expected to further enhance their capabilities to satisfy the growing market needs for ubiquitous localisation.

In this context, it appears necessary to develop a proper understanding of the emerging trends in alternative PNT technologies. With a renewed interest in LEO constellations, investigations for innovative space-based PNT infrastructures need to consider LEO-based PNT, and their potential to complement a GNSS backbone with, for example, improved reactivity to new user needs and new capabilities.

The objective is to perform a system study of LEO-based PNT systems able to complement a GNSS backbone, like Galileo and/or multi-GNSS, with valuable capabilities, in particular but not limited to:

• Improved resilience (robustness and adaptation), Improved coverage of emerging needs and use cases, as well as improved penetration in challenging environment

• Short Time-to-market for new features, functionalities and services,

The activity shall focus on efficient and affordable implementations of a LEO-based PNT, leveraged by the capabilities of large, low cost constellations and modern user segments. All aspects relating to a modern space-based PNT system will be considered, not only the space segment, but also:

• Efficient, future-proof M&C segment architecture,

• State-of-the-art user segment technologies

• Interoperability and use of external systems

The results of the study should provide guidance for planning future activities including for example: development of both system and technological enablers, testing and proof of concept activities and further studies along the entire value chain. They will therefore include (but are not limited to): 

• Consolidation of use cases, and state-of-the-art in complementary/alternative PNT

• Identification of candidate system scenarios for complementary PNT in LEO

• Technical investigation of these scenarios (including ground mission segment and user segment aspects), mapping to the agreed use cases, and assessment of overall system ability to provide added-value as a complement to a GNSS backbone

• Conclusions and recommendations for future activities.