Five years ago this month, NASA's Terra satellite began measuring Earth's vital signs with accuracy, precision, and resolution the world had never seen before. This great Earth observing satellite was launched to look at many aspects of Earth's changing climate. Terra has been very successful in its mission to advance our understanding of Earth's climate system to help improve our quality of life.

Launched on December 18, 1999, Terra's five onboard instruments began science operations in February 2000. Terra's goal is to assess the health of the planet by providing comprehensive information about Earth's land, oceans and atmosphere. Terra orbits the Earth more than fourteen times a day and observes nearly the entire globe.

"Terra is Earth science's first great observatory," said Bruce Wielicki, Senior Scientist for Earth Science at NASA's Langley Research Center, Hampton, Va. who uses Terra data to monitor how much of the Sun's energy is being absorbed and reflected by Earth. "Terra has provided the most comprehensive and the most accurate global view of the Earth's climate on record. And it has pioneered the first comprehensive, multi-instrument approach to climate change research."

Sending home roughly 1 million megabytes of data per day, Terra is helping scientists all over the world tackle important questions about the causes and effects of environmental changes. While the mission is still in the process of fulfilling its main science objectives, Terra's portfolio of achievements to date already makes the mission a resounding success.

Terra monitors movements of carbon through Earth's climate system. Humans annually release more than 7 billion tons of carbon into the atmosphere through the burning of fossil fuels. Yet, scientists cannot account for where all this carbon ends up. Between 1 and 2 billion metric tons of carbon per year are "missing" from the global carbon budget. Terra is providing scientists with some important clues to help them solve the mystery of the missing carbon.

Terra data have also helped improve weather prediction. Terra's ability to track the speed, direction, and height of clouds allows scientists to accurately measure how strong and which way the wind is blowing over areas where they had little data before, such as over oceans.

Two years ago meteorologists at the European Centre for Medium-Range Weather Forecasts (ECMWF) began using Terra MODIS data to track clouds over the Arctic Circle. The result is a 3-hour advance in the accuracy of forecasts in that region.

Terra provides scientists with much more accurate information on Earth's albedo (or reflected sunlight) over areas where before they could only make educated guesses. The end result is improved weather forecasts in Northern Africa, the Arabian Peninsula, and across great expanses of the mostly uninhabited northern boreal forests of North America and Asia.

The mission's unique combination of sensors allows scientists worldwide to monitor fires, floods, severe storms, and volcanic activity in near real time. Today organizations all over the world are using data from four different instruments aboard Terra as part of their ongoing efforts to monitor the causes and effects of natural hazards.

The U.S. Environmental Protection Agency (EPA) uses Terra data to help monitor air quality. EPA scientists found that Terra's combined precision and big picture perspective far exceed their ability to measure aerosol and carbon monoxide pollution from individual locations all across the United States.

Terra also watches cloud and tiny pollutant particle (aerosol) concentrations in the air; snow and ice cover on the surface, and gives scientists an eye on areas of expanding deserts and cities, and deforestation.

Terra's view of Earth from space is one that is critical in understanding all of the changes occurring in Earth's land, oceans, atmosphere and overall climate.

For more information about Terra, please visit on the Internet:

http://terra.nasa.gov/