Galileo characterization as Input to H-ARAIM and SBAS DFMC

Abstract

The characterization of Galileo Open Service signal-in-space (SiS) represents an essential input to Safety-of-Life (SoL) applications like Horizontal ARAIM (Advanced Receiver Autonomous Integrity Monitoring) and SBAS (Satellite Based Augmentation System) in particular EGNOS V3. This paper describes the IFMEA (Integrity Failure Mode and Effect Analysis) process that has been implemented for Galileo in order to conduct in a structured way the analysis of events critical for Safety-of-Life applications (referred to as Feared Events, FE) based on accumulated measurement history and design documentation analysis. The different steps of the established process are described which encompass measurement collection and post-processing, design analysis, root cause identification, reporting and archiving in form of a database. The process is leading to the identification of improvement recommendations in order to mitigate the re-occurrence of observed events. Moreover this paper provides insight into the Galileo Feared Event characterization, along with an analysis versus overall Safety-of-Life needs and the extrapolation to future Galileo configurations. It comprises the identification of anomalies in the satellites’ signal-in-space that could impact the positioning integrity. Several SiS threat offline monitors have been developed for the Galileo Feared Event characterization that allow identifying anomalies in both the navigation message and code and carrier phase observations. The focus is put on the characterization results in terms of Feared Event probabilities of occurrence and related magnitudes.The underlying mathematical approach for the derivation of the Feared Eventprobabilities as a function of the number of Feared Events and the observation period is described in this paper.The characterization results confirm the high quality of the code and carrier phase signals (based on an observation period of about 3.5 years of the Galileo constellation). For the message related anomalies including the broadcast orbit and clock prediction errors, the latest results are limited due to a limited observation period (about 2.5 years of Galileo constellation after the declaration of Galileo Initial Services). After extrapolation to a future Galileo configuration, the Feared Event probabilities achieve low and very promising levels.