The launch of Terra marks the beginning of humankind's comprehensive monitoring of solar radiation, the atmosphere, the oceans, and the Earth's continents from a single space-based platform. Its mission objectives stem from NASA's Earth Science research strategies and the Terra instruments' capabilities. The science priorities of EOS are to provide global observations and scientific understanding of:

• Land cover change and global productivity—including trends and patterns of change in regional land cover, biodiversity, and global primary productivity;

• Seasonal-to-interannual climate predictions that improve forecasts of the timing and geographical extent of transient climate anomalies;

• Natural hazards—including disaster characterization and risk reduction from wildfires, volcanoes, floods, and droughts;

• Long-term climate variability, to help scientists identify the mechanisms and factors that determine long-term climate variation and trends, including human impacts; and

• Atmospheric ozone, to help scientists detect changes, causes, and consequences of changes in atmospheric ozone.

	Global maps of the aerosol loading derived from TOMS data (top) over land and ocean, and from AVHRR data over the oceans (bottom). The regions of high aerosol concentrations are indicated by red colors. Note the dust aerosol advected westward from Africa, and the heavy dust in the Arabian Peninsula (image courtesy of Jay Herman, GSFC and Joe Prospero, University of Miami).

Specific objectives of Terra and their implementation include the following:

1. Provide the first measurements of the global/seasonal distribution of key Earth and atmosphere parameters, which include global bio-productivity (land and oceans); land use; land cover, snow and ice; global surface temperature—day and night; clouds (macrophysics, microphysics, and radiative effects); radiative energy fluxes; aerosol properties and water vapor, fire occurrence, and trace gases.

   Begin to assimilate data from Terra and Landsat-7 into regional process studies and models. Begin to detect annual changes in land use and deforestation.

   Generate a new set of state distributions of geophysical parameters in combination with Jason-1 and Aqua (EOS PM-1) data.

   Global maps of the aerosol loading derived from TOMS data (top) over land and ocean, and from AVHRR data over the oceans (bottom). The regions of high aerosol concentrations are indicated by red colors. Note the dust aerosol advected westward from Africa, and the heavy dust in the Arabian Peninsula (image courtesy of Jay Herman, GSFC and Joe Prospero, University of Miami).

2. Improve our ability to detect human impacts on climate, identify "fingerprints" of human activity on climate, and predict climate change by using the updated global distributions of land use change, aerosols, water vapor, clouds and radiation, trace gases, and oceanic productivity in global climate models.

   Later, these comparisons will be repeated together with Landsat-7, SAGE-III, Jason-1, and Aqua data.

3. Provide observations that will improve forecasts of the timing and geographical extent of transient climatic anomalies. Investigate the correlation between the regional and annual variations of clouds, aerosols, water vapor, biota in land and oceans, fires and trace gases, the radiation field, and major climatic events such as El Niño, volcanic activity, etc.

4. Improve seasonal and interannual predictions using Terra (and later Jason-1 and Aqua) data.

5. Develop technologies for disaster prediction, characterization, and risk reduction from wild-fires, volcanoes, floods, and droughts.

6. Start long-term monitoring of the change in global climate and environmental change.

EOS identified high-priority measurements needed for a better understanding of each of the Earth system components—the atmosphere, the land, the oceans, the cryosphere, and the solar driving force. To quantify changes in the Earth system, EOS will provide systematic, continuous observations from low Earth orbit for the bulk of these measurements for a minimum of 18 years. The following is a list of these key measurements; those that will be provided specifically by Terra instruments are in bold text.