ESA Earth Explorer 8 candidate selected in November 2010 for Phase-A/B1 feasibility work, CarbonSat would image and quantify atmospheric carbon dioxide and methane to improve understanding of their natural and human sources, sinks and links to climate change. ESA later selected FLEX as Earth Explorer 8 in November 2015; CarbonSat remains a documented research concept whose preparatory work informed later greenhouse-gas observation efforts.