The present chapter puts relevant information from the Copernicus CO₂ Monitoring Mission Requirements Document and from the three reports of the Copernicus Expert group and of the Task forces in perspective in the context of the prototype system which is being designed in CHE. It successively discusses the satellite CO₂ retrievals, the satellite non-CO₂ observations, the ground-based remote sensing observations and the in situ and flask-sampling observations. It highlights the large research needs for the identification of the role of each relevant Earth observation type in the Copernicus CO₂ support capacity system and for the modelling capability associated to the main ones.