Following the successful implementation of the ERS satellites and Envisat, which address Earth science issues of a global nature, Earth Explorers are smaller research missions dedicated to specific aspects of our Earth environment. 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 and three are Opportunity missions.

GOCE (Gravity Field and Steady-State Ocean Explorer)
Core mission - Launched on 17 March 2009

How does the gravity field affect ocean currents and sea level?

GOCE is dedicated to measuring the Earth's gravity field and modelling the geoid with unprecedented accuracy and spatial resolution to advance our knowledge of ocean circulation, which plays a crucial role in energy exchanges around the globe, sea-level change and Earth interior processes. GOCE will also make significant advances in the field of geodesy and surveying.

SMOS (Soil Moisture and Ocean Salinity)
Opportunity mission - Launched on 2 November 2009

Is climate change accelerating the water cycle?

SMOS will observe soil moisture over the Earth's landmasses and salinity over the oceans. Soil moisture data are urgently required for hydrological studies and data on ocean salinity are vital for improving our understanding of ocean circulation patterns.

CryoSat-2
Opportunity mission - Launched on 8 April 2010

Are the ice caps shrinking?

CryoSat-2 will acquire accurate measurements of the thickness of floating sea-ice so that seasonal to inter-annual variations can be detected, and will also survey the surface of continental ice sheets to detect small elevation changes. It will determine regional trends in Arctic perennial sea-ice thickness and mass, and determine the contribution that the Antarctic and Greenland ice sheets are making to mean global rise in sea level. CryoSat-2 replaces CryoSat which was lost due to a launch failure in October 2005.

Swarm
Opportunity mission - Scheduled for launch in 2012

How fast is the Earth's magnetic shield weakening against solar radiation?

Swarm is a constellation of three satellites that will provide high-precision and high-resolution measurements of the strength and direction of the Earth's magnetic field. The geomagnetic field models resulting from the Swarm mission will provide new insights into the Earth's interior, further our understanding of atmospheric processes related to climate and weather, and will also have practical applications in many different areas such as space weather and radiation hazards.

ADM-Aeolus (Atmospheric Dynamics Mission)
Core mission - Scheduled for launch in 2014

How does measuring the wind improve weather forecasting?

ADM-Aeolus will be the first space mission to measure wind profiles on a global scale. It will improve the accuracy of numerical weather forecasting and advance our understanding of atmospheric dynamics and processes relevant to climate variability and climate modelling.

EarthCARE (Earth Clouds, Aerosols and Radiation Explorer)
Core mission - Scheduled for launch in 2015

To what extent do clouds and aerosols influence global warming?

EarthCARE is being implemented in cooperation with the Japanese Aerospace Exploration Agency (JAXA), and addresses the need for a better understanding of the interactions between cloud, radiative and aerosol processes that play a role in climate regulation.

Future missions

Earth Explorer 7: Following ESA's Call for Ideas for the seventh Earth Explorer in 2005 and the subsequent selection in 2009, three missions – BIOMASS, CoReH2O and PREMIER are undergoing the next stage of development (feasibility study).

Earth Explorer 8: As a result of the Call for Proposals for the eighth Earth Explorer released in October 2009, the Florescence Explorer (FLEX) and CarbonSat missions have been approved to move forward to Phase A/B1. Approval was given by ESA's Earth Observation Programme Board on 24 November 2010.