I will first motivate the need to conduct massive spectroscopic surveys to learn about the 3D distribution of galaxies. From these measurements we can then derive important parameter on the distribution of galaxies such as the Baryonic Acoustic Oscillation, and the Redshift Space distorsion. These measurements are key to learn on the universe content and constrain cosmological models.
In a second part, I will explain how we can achieve these measurements and I will describe the difference techniques that can be used to conduct a massive spectroscopic redshift survey. I will in particular describes the work conducted at EPFL for the DESI, MOONS and SDSS-V fiber position robots.
I will open the discussion for the future possible spectroscopic surveys.
