Examples of user algorithms implementing ARAIM techniques for integrity performance prediction, procedures development and pre-flight operations

Abstract

Abstract-Advanced Receiver Autonomous Integrity Monitoring (ARAIM) is a new Aircraft Based Augmentation System (ABAS) technique, firstly presented in the two reports of the GNSS Evolutionary Architecture Study (GEAS). TheARAIM technique offers the opportunity to enable GNSS receivers to serve as a primary means of navigation, worldwide, for precision approach down to LPV-200 operation, while at the same time potentially reducing the support which has to be provided by Ground and Satellite Based Augmented Systems (GBAS and SBAS). ARAIM is based on the Solution Separation Method and implements other techniques, such as:• Frequency diversity, using dual-frequency measurements.• Geometry diversity, using multi-constellation configurations, combining the available satellites from the new and renewed constellations (GPS, Galileo and GLONASS, but potentially Beidou too).• Integrity Support Message, describing both the nominal error behavior and the probability of fault of one or more satellites.Previous work analysed ARAIM performance, clearly showing the potential of this new architectures to provide the Required Navigation Performance for LPV 200. However, almost all of the studies have been performed with respect to fixed points on a grid on the Earth's surface, with full view of the sky, evaluating ARAIM performance from a geometrical point of view and using nominal performance in simulated scenarios which last several days. Though, the operational configuration was not examined; attitude changes from manoeuvres, obscuration by the aircraft body and shadowing from the surrounding environment could all affect the incoming signal from the GNSS constellations, leading to configurations that could adversely affect the real performance. In [8] we presented the ARAIM performance in simulated operational configurations. The results showed that the aircraft attitude and the surrounding environment affect the performance of the ARAIM algorithm; each satellite lost generates a peak in the performance parameters that depends on the total number of satellites in view, their relative geometry and on the number of satellites lost at the same time. The main outcome of this research is the identification that the ideal scenario would be to have a triconstellation system that provides at the same time high redundancy, reliability and increased safety margin.In this paper, we summarise and continue the work performed in our project. In our research we developed four different algorithms that integrate the ARAIM technique for performance prediction analysis. These algorithms could usefully be implemented: •In the design of instrument approach procedures. The algorithms could be used to improve the procedure of the development of new instrument approaches, reducing time, effort and costs.• In the aircraft Flight Management Systems. The algorithms could support the pilots in the pre-flight briefing, highlighting possible integrity outage in advance and allowing them to select a different approach or making them aware of the need to uti...