For the past decade NASA's Terra spacecraft has examined key attributes of Earth's land, oceans and atmosphere much the way a doctor tracks a patient's vital signs. And like planetary physicians, Terra scientists have used this continuous stream of information to make an array of new diagnoses about the planet's changing climate and environment.
The flagship of NASA's Earth-observing fleet, Terra was the first spacecraft designed to carry a suite of instruments uniquely able to accumulate an ongoing record of a wide variety of planetary health indicators—from carbon storage and cloud cover to wildfires and oil spills. Indeed, Terra's five onboard sensors have scanned the entire globe every one to two days since they saw "first light" on February 24, 2000, and are expected to continue at that pace for another five years [see "Monitoring Earth's Vital Signs," in the April 2000 issue of Scientific American ].
Taking stock of Terra's first 10 years, scientists gathered in May at mission control, NASA Goddard Space Flight Center in Greenbelt, Md., to showcase some of the mission's premier discoveries—among them, that droughts are decreasing the planet's carbon storage capacity and that pollution travels much higher and farther than once assumed. The ability of satellite operators to point Terra's sensors at specific targets has aided disaster-relief efforts with an unprecedented ability to track natural hazards as they unfold: the eruption of Eyjafjallajökull volcano in Iceland and the recent oil spill in the Gulf of Mexico are just two examples. Time-series images taken over the course of Terra mission have made for compelling visual documentation of longer-term changes to the environment and landscape as well.
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For many of the indicators that Terra tracks, composite global maps and raw data sets are available for every month of mission. In other cases it is simply the spectacular, high-resolution imagery that tells the story. Myriad examples are archived and posted regularly on the
Terra mission Web site and that of the NASA Earth Observatory. We gathered some of our favorites for the series that follows.