With the start of the SENTINEL era, an unprecedented amount of Earth Observation (EO) data has become available. Currently there is no consistent but extendible and adaptable framework to integrate observations from different sensors in order to obtain the best possible estimate of the land surface state. MULTIPY proposes a solution to this challenge. The project will develop an efficient and fully traceable platform that uses state-of-the-art physical radiative transfer models, within advanced data assimilation (DA) concepts, to consistently acquire, interpret and produce a continuous stream of high spatial and temporal resolution estimates of land surface parameters, fully characterized. These inferences on the state of the land surface will be the result from the coherent joint interpretation of the observations from the different Sentinels, as well as other 3rd party missions (e.g. ProbaV, Landsat, MODIS). This implies that optical data are linked to passive microwave data to help better constrain land surface variables that these domains have in become. Moreover, coarse resolution data (e.g. from MODIS) help to constrain high resolution SENTINEL data, achieving information-rich retrieval that is consistent with all data sources. To achieve consistently, also a generic atmospheric correction scheme is developed to retain full consistently from data access to land surface products. Finally, the MULTIPLY platform also allows users to exchange components as plug-ins according to their needs. Altogether, the MULTIPLY platform will pave the way towards services, such as the Copernicus services, based on the best possible estimates of the land surface state.