This work programme addresses pressing issues in both observational and theoretical cosmology. The main goal is to use the Baryon Acoustic Scale of Oscillations (BAO) to pin down the nature of the Dark Energy (DE) component.The BAO scale is a powerful probe of DE properties. It constrains geometrical as well as dynamical tracers of the Universe’s evolution, and can break the long-standing degeneracy between dark energy and spatial curvature.The observational component is strongly related to data analysis of the SDSS survey the most successful of astronomical surveys in history, in particular the BOSS survey that Dr. Cortes is a part of. It is also related to the design and conceptual planning of BOSS’s next-generation experiment, the GROUND-BASED SPECTROSCOPIC BigBOSS survey that Dr. Cortes is also a part of.BigBOSS is currently being planned at Dr. Cortês’ institution, Lawrence Berkeley National Laboratory and will extend the studies of BOSS to even earlier stages in the history of the universe, leveraging the full power of BAO to the next level.The theoretical component will play an essential role in ensuring the design of future probes of DE is optimized to obtain the best leverage of future data in the constraining of DE models.This work constitutes a breakthrough in the way BAO data, in particular from the Lyman-Alpha Forest, is currently treated and converted in constraints on DE.The goal of the project is to promote the transfer of expertise of analysis of BAO data between the US and the European Union, through the EDINBURGH INSTITUTE FOR ASTRONOMY.It is also highly beneficial for European Science Community as a whole to exchange expertize in survey planning with the US, in consultation with community-led teams to define the optimal survey with a broad and rich science yield.