• SPECTRA (Surface Processes and Ecosystem Changes Through Response Analysis)—a mission that will study the role of terrestrial vegetation in the global carbon cycle and its response to climate variability.

• WALES (Water vApour and Lidar Experiment in Space)—a mission to provide a better understanding of the distribution of atmospheric water vapor in the troposphere and lower stratosphere.

Additional information is available online:

<http://www.esa.int/export/esaLP/ASESMYNW9SC_earthcare_0.html>

<http://www.esa.int/export/esaLP/ASE12YNW9SC_spectra_0.html>

<http://www.esa.int/export/esaLP/ASE77YNW9SC_wales_0.html>

“Opportunity” missions are not necessarily ESA-led and are on a smaller scale than “Core” missions. As part of the second cycle of Earth Explorers Opportunity Missions, three new candidate proposals were selected to enter Phase A (feasibility study) in May 2002. The three missions selected are ACE+, EGPM, and SWARM:

• ACE+ (Atmospheric and Climate Explorer)—a climatological mission that will measure variations and changes in global atmospheric temperature and water vapor.

• EGPM (European contribution to Global Precipitation Mission)—a mission element within an international initiative to measure precipitation (e.g., rain, snowfall) all over Earth every 3 hours.

• SWARM—a constellation of small satellites to study the dynamics of Earth’s magnetic field and its interactions with the Earth system.

It is expected that the feasibility studies will be complete by mid-2004, after which two of the three missions will be selected for implementation. The launch of the first mission is envisaged for 2008.

Additional information is available online:

<http://www.esa.int/export/esaLP/ESAILYJE43D_ace_0.html>

<http://www.esa.int/export/esaLP/ESAGKZJE43D_egpm_0.html>

<http://www.esa.int/export/esaLP/ESA3QZJE43D_swarm_0.html>