The Monitor project has been designed to monitor ionospheric events that would allow evaluating its impact on European GNSS Systems. It includes a network of ionospheric scintillation monitoring stations in various locations covering different latitude regions and its routine data collection; and, the generation and collection of relevant products that allow understanding ionospheric perturbations from the ionosphere. This paper presents an overview of the project and how it is able to support SBAS systems, including also the analysis of perturbed days in EGNOS during recent St. Patrick’s Day 2015 Geomagnetic Storm. Additionally, the potential impact of this recent ionospheric event on GBAS systems will be analyzed as well. Indeed, Monitor is a project from the European Space Agency’s GNSS Evolutions Programme started in 2010, dedicated to the collection, processing and archiving of ionospheric data and products during active periods of solar activity, to the development of improved scintillation monitoring instrumentation and to the establishment of a scintillation monitoring network, in order to build the infrastructure allowing to analyse the impact of the ionosphere on European GNSS (EGNOS and Galileo) system performance. The second phase of the Monitor project started in 2014, with the objectives: to achieve a simple and robust data collection, processing and access, to implement a flexible data access policy, to enlarge the scintillation monitoring network with new stations, and integrating data from the CNES SAGAIE network, and improved monitoring instrumentation, to generate automatic comprehensive reporting; and with main focus to support EGNOS current system and future evolutions.Monitor has the ability to support the assessment of the relationship of an SBAS system (EGNOS, WAAS) to the ionosphere’s variability, analysing in detail the ionospheric a number of perturbations cases degraded SBAS system performance. (...)