The impacts of multi-satellite altimetry on the representation of eddies across the spectrum of meso-scales from 500 km to the order of 10 km are assessed. Horizontal grid spacing down to the order of 1km is now often used for regional forecasting models. To assimilate satellite altimetry data into such fine resolution models, we need to deal with a set of particular difficulties. Among those difficulties are scale differences among sea surface height, salinity and temperature fields, density compensation, spatial localization and temporal intermittency of small mesoscale and sub-mesoscale systems, and others. Leveraging a real-time multi-scale three-dimensional variational data assimilation (MS-3DVAR) and forecasting system, which has successfully supported the Salinity Processes in the Upper Ocean Regional Study (SPURS) field campaign in the North Atlantic Ocean, and the SPURS multi-scale observing network, we illustrate those difficulties, address methodologies and formulations to deal with those difficulties, and demonstrate positive impacts of multi-satellite altimetry on the representation of mesoscale and sub-mesoscale eddies whose scales can be down to a few ten km.