Capable constellations of SmallSats can improve spatial and temporal coverage of the observing system. Current research was intended to optimize future SmallSats constellations through Observational System Simulation Experiment (OSSE), by testing impact of EON-MW on the global Numerical Weather Prediction (i.e., NCEP Global Data Assimilation System and Global Forecast System). EON-MW was simulated with the Community Radiative Transfer Model (CRTM) in high- and low-inclination orbits, using the NASA GEOS-5 Nature Run (G5NR). Different constellations of EON-MW were added to two baseline configurations: The first configuration is labeled Control and has mid-morning and afternoon orbits; the other configuration is labeled 1Polar and is a data-gap scenario where the afternoon orbit is missing. The constellations explored in this study assess using EON-MW in several orbits, including high and low inclination ones. Preliminary results show that the proposed SmallSats constellations, when compared to the true state of the atmosphere in the G5NR, present a real added value to the global analyses and forecasts.