Global Navigation Satellite Systems (GNSS, e.g. GPS or Galileo) allow to measure positions on Earth’s surface. Permanently tracking GNSS reference stations installed throughout the world provide reliable points of reference for accurate positioning. The Royal Observatory of Belgium (ROB/KSB/ORB) maintains unique repositories containing decades of GNSS observation data from Belgian stations as well as stationsbelonging to the European GNSS network (EUREF).Although ROB’s EUREF repository is currently used by various communities (e.g. geodesists, mapping agencies, etc.), the procedures to find and access the data are rather complex and not accessible to machines. Despite the fact that the GNSS data originate from a significant number of data providers (~100), provenance information is lacking. Data licenses are only seldom available and no data citation procedure is in place to recognize the merit of researchers providing the GNSS data. Hence, ROB’s EUREF GNSS repository requires additional efforts to upgrade its data management procedures to align with current best practices in Open Data. These need to be extended to the Belgian data repository which is currently not publicly open.The objectives of FAIR-GNSS are therefore to,• Facilitate access and re-use of, and increase trust in, ROB’s GNSS data repositories,• Support the preservation of its data,• Contribute to the standardization of GNSS data citation• Create a modern open data portal for European and Belgian GNSS data.FAIR-GNSS willuse the FAIR principles, with the aim to make data more Findable, Accessible, Interoperable, and Re-usable (FAIR), and apply it to GNSS data management. FAIR-GNSS will take advantage of the most recent guidelines such as the EC action plan “Turning FAIR into Reality” and the TRUST principles to prepare ROB’s GNSS repositories to become Trustworthy and FAIR-enabling repositories. These principles do address all the issues arising from the current management of ROB’s GNSS data and its data repositories. Indeed, as highlighted in the EC action plan and in the TRUST white paper, the steps needed to move towards a CoreTrustSealcertification can be helpful as a standardized process to ensure both data preservation and baseline data FAIRness.While there is international consensus on FAIR principles, there has been no international effort focusing on FAIR GNSS data yet. FAIR-GNSS aimsat turning GNSS data into FAIR Data Objects,among others, complete them with metadata and Persistent Identifiers (PID)e.g. Digital Object Identifiers (DOIs). Researchers will benefit from the citation metrics associated to GNSS data, as it will easily show the impact of their research data while providing evidence of their usage.Finally, building on ROB’s upgraded GNSS data and repositories (EUREF and Belgian), FAIR-GNSS will create a new open data portal. As a consequence, by making GNSS data more readily available, accessible and citable, FAIR-GNSS will maximize ROB’s data re-use. In its practical applications, this will also increase trust in the GNSS data and encourage SMEs, industries and start-ups to use them and innovate.