In the last years, there has been fast progress in satellite on-board computing achieved by the satellite telecommunication industry. On-board processors are more performant, with less mass, volume and power consumption.
As regards current and evolving space-based PNT data layer services (e.g. private or public GNSS data augmentations), they usually retransmit data computed on-ground via satellite and their architectures do not exploit the benefits that technological innovation in on-board processing could bring against new threats and challenges. These benefits may range from reduction of latency for data collection, processing and broadcast to increased robustness against physical and cyber-attacks, as jamming and spoofing of the satellite up-link.
The main objective of the activity is to study new, innovative concepts and trade-off main design drivers for a PNT data layer system based on on-board processing, alternative to conventional on-ground computation based systems.
Alternative architectural concepts could consist of up-linking Monitoring Station (MS) data directly to satellites where PNT data layer messages are processed on-board and broadcast to users. In this architectural concept, the following features are typically envisaged:

•  each Monitoring Station is equipped with a satellite uplink terminal;
•  there is no real-time terrestrial network to transmit data to a central processing facility on-ground;
•  PNT data layer messages and signals are processed and generated on-board, with up-link data received through e.g. a spot beam antenna.

The tasks to be performed will include:

•  definition of high-level architectural concepts with particular focus on the payload features and main constituents, identifying main functions and data flows for each component and performing main system trade-off’s;
•  analysis of achievable end-to-end performance, studying the cases where improvements derived from alternative architectures are expected, for instance on data latency, and providing insight into the main design drivers;
•  assessment of status of existing technology vis-à-vis functional and architectural needs, identifying areas for technology evolutions such as radiation-hardened space computer or on-board processing capabilities;
•  identification of potential improvements in robustness versus cyber-attacks, jamming and spoofing.

The main results of the activity will provide an assessment of the interest in alternative architectures based on on-board processing, with insight in the main architectural trade-off’s and identification of areas where technology evolution is a prerequisite.
Results from previous related ESA activities will be duly considered and assessed. Close coordination with EUSPA will be ensured.