Following the success of the ERS satellites and Envisat, which addressed Earth science issues of a global nature, Earth Explorers are smaller research missions dedicated to specific aspects of our Earth environment whilst demonstrating new technology in space.
Earth Explorer missions focus on the atmosphere, biosphere, hydrosphere, cryosphere and the Earth's interior with the overall emphasis on learning more about the interactions between these components and the impact that human activity is having on natural Earth processes.
Designed for research purposes, Earth Explorer missions fall into two categories: 'Core' missions addressing specific areas of great scientific interest, and faster, lower cost 'Opportunity' missions to address areas of immediate environmental concern.
Of the six Earth Explorers selected for implementation, three are Core missions (GOCE, ADM-Aeolus and EarthCare) and three are Opportunity missions (SMOS, CryoSat and Swarm). In 2013, the Biomass mission was selected to go forward as ESA's seventh Earth Explorer.