Space Weather Impacts on the Ground Based Augmentation System

The Ground Based Augmentation System (GBAS) is a single frequency short baseline Differential GNSS system which has been developed to support aircraft approach and automatic landings. Ionospheric phenomena that can cause a large change in relative delay over a relatively short baseline (i.e. a few meters over a few kilometers) can be quite problematic for the system. A large amount of work was been done over the course of the last 7 years to characterize the impact of ionospheric anomalies on the performance of the system and to devise mitigations to address the problem. Mitigations have been found to enable GBAS to be used to support approach and landings in all conditions, there are some operational uses of GBAS for which the threat from ionospheric anomalies is still a problem. For those applications space weather monitoring and forecasting / now-casting of ionospheric conditions may be necessary. This presentation will give a brief overview of the problem of ionospheric anomalies for GBAS, outline the mitigations implemented to date, and discuss the outstanding problems that may require space weather monitoring as part of the solution. Finally the presentation will talk about what appropriate space weather monitoring might look like and how such monitoring could be integrated into operational procedures in order to mitigate the risk misleading guidance caused by an ionospheric anomaly.