GLAD

GLobal ARAIM for Dual-Constellation

The Advanced RAIM (ARAIM) concept extends the traditional legacy GPS single frequency Receiver Autonomous Integrity Monitoring (RAIM) by using multiple GNSS constellations that may include signals from the same satellite transmitting more than one frequency. The Galileo constellation, in addition to GPS, provides a Dual Frequency Multi-Constellation (DFMC) system that allows for robustness and redundancy. 

In the aviation sector, when DFMC is supported by a Satellite Based Augmentation System (SBAS) and ARAIM, satellite availability is leveraged with accuracy in position and the associated integrity and continuity elevated in terms of radio navigation performance. 

Concept wise, each GNSS Constellation Service Provider (CSP) will transmit an Integrity Support Message (ISM) to broadcast integrity information associated with its own system. 

The airborne receiver’s ARAIM algorithm processes this information to gain sufficient confidence in the information provided by the specific GNSS constellation in order to meet required safety criteria in terms of lateral and vertical guidance, thereby addressing the requirement for all phases of flight up to Category I (CAT I) precision approach capability/localiser performance with vertical guidance (LPV) 200 approach globally in the future.

The GLAD project aims to foster the development of the ARAIM concept by prototyping the algorithm within critical components of the Collins’ GLU-2100 Multi-Mode Receiver (MMR), followed by testing and assessing the performance of the algorithm. In addition, the project focuses on concepts of operations (CONOPS) using ARAIM and collaborated with Air Navigation Service Providers (ANSPs) to engage and understand the requirements for airport operations. Standardisation activities within GNSS working groups are also within the scope.

Challenge and technical solution

During the GLAD project timeframe, the team successfully conducted ground experiments demonstrating real-time horizontal and vertical ARAIM performance, with a horizontal precision of 0.3 NM and vertical precision supporting LPV-200. 

This paved the way for future benefits which include significant contributions to improvements in position integrity, and to underpinning the economic (e.g., fuel and time), environmental (e.g., CO2), and safety aspects required by the aviation industry.