CPI proposes to develop an innovative, generalized retrieval algorithm and analysis tool (GRANT) that will facilitate analysis of remote sensing data from both terrestrial and planetary atmospheres, and that is applicable to a wide range of NASA's remote sensing missions. GRANT will be based upon a generic and flexible implementation of the optimal estimation inversion technique for atmospheric retrievals (OPT), and be driven by a state-of-the-art FUV-NIR atmospheric radiance model (AURIC) for its forward model. GRANT will possess a flexible, user-configurable sensor model for generating realistic simulated data that tailors the retrieval algorithm to a specific sensor and measurement system. The anticipated Phase I result will be a working prototype analysis tool for application to terrestrial and planetary atmospheres. This prototype will be validated against a focused set of existing retrieval algorithms using remote sensing data from several NASA and DoD sensors. Phase II will yield a prototype that includes additional retrievable geophysical parameters, has a graphical user interface, incorporates a detailed formal error analysis capability, and has improved forward modeling capabilities such as energetic particle transport and enhanced Visible/IR modeling. The TRL levels at the start and end of Phase I are estimated to be 3 and 4, respectively.