The study relied on various state-of-the-art numerical tools (RT model, assimilation OSSE and NWP forecast systems) to explore the possible impact of a Geosounder mission on the retrieval of humidity and forecast. The study showcases that some specifications are valid for such an endeavor and some needs to be refined. Future works should be directed towards a more complex information content analysis with an all sky OSSE set up and maybe a multispectral/hyperspectral perspective on the channel selection.