The ESA project “Fiducial Reference Measurement for Soil Moisture (FRM4SM)” (May 2021 – May 2023) aims to identify and create standards for independent, fully characterized, accurate and traceable in-situ soil moisture measurements with corresponding independent validation methods and uncertainty estimations towards a maximum Return On Investment (ROI) for a satellite mission. The ultimate goal is to deliver confidence in soil moisture data products for the whole duration of a satellite mission. Ground reference data from the International Soil Moisture Network (ISMN: https://ismn.earth/en/, Dorigo et al., 2021: https://hess.copernicus.org/articles/25/5749/2021/) builds the in-situ base for this study by following, building and improving the integrated standardized measurement protocols and quality techniques for in-situ soil moisture data. SI traceability, error propagation and data quality are thoroughly examined to better understand uncertainty estimations supporting earth observation (EO) satellite mission results. Investigations for independent validation methods will focus efforts towards the Soil Moisture Ocean Salinity (SMOS: https://earth.esa.int/eogateway/missions/smos) mission from ESA at the resolution of passive space borne radiometer within the FRM4SM project. Indeed, SMOS is characterized by a footprint of ~43km in average, which implies that the surface observed by the instrument is very different from the in-situ measurements obtained by local scale. This project will investigate the spatiotemporal scale mismatch between the SMOS resolution and the in-situ representativeness. Based on the global validation of SMOS on the ISMN, several aspect are studied here as the validation sensitivity to the in-situ configuration (probes depth, technologies…), the geophysical SMOS footprint characteristics (landcover, soil characteristics…), or the effect of the different sampling strategy (in-situ driven vs. satellite driven). The Quality Assurance for Soil Moisture (QA4SM: https://qa4sm.eu/) service is an easy-to-use interface for the comparison of satellite soil moisture data against land surface models and in-situ data (ISMN). This service targets to implement all created FRM protocols from ground measurement to validation methods created within the FRM4SM project. Within this session, we want introduce ESA`s Fiducial Reference Measurements for Soil Moisture (FRM4SM) project, working on the identification and guidlines of SI traceable, accurate, high quality in-situ soil moisture data towards a fully traceable satellite validation service.