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With a treasure trove of almost 30 years of remote Earth observations, NASA has opened grand vistas for research in a wide variety of fields. NASA’s global observations, preserved and archived for long-term comparisons of change over time, has enabled scientists to develop a better understanding about how the atmosphere, land, oceans and life work together systemically.

This week, in conjunction with Earth Day, NASA releases a stunning new collection of images of the Earth, derived from sophisticated research hardware on orbit.

The legacy of remote sensing began in earnest in 1972 with the launch of the first Landsat satellite. Six more followed with the latest, Landsat 7, rocketing into space in April 1999.

Eight months after Landsat 7’s launch, NASA orbited Terra, the flagship in its series of Earth Observing System spacecraft. This multi-national satellite is helping researchers pursue some of the grandest and most complex questions about our home planet, including cutting edge research into climate change.

NASA added the latest in this long line of remote sensing spacecraft in November 2000 when it lauched the technology pathfinder, EO-1.

From Landsat 1 to EO-1, these increasingly powerful and sophisticated satellites provide high-resolution images of the Earth below and researchers are seeing things they’ve never seen before, studying everything from city growth to climate change.

This long-term record of data, part of a global research effort NASA calls the Earth Science Enterprise, seeks to acquire an understanding of the changes to our planet.

Among the changes recorded by these orbiting sentinels:

Tracing Urban Growth

When a city grows, far more than buildings and roads change. Atmospheric conditions, vegetation, available fresh water and many other features of the natural world change in response to increased urbanization, and a careful record of that change is imperative for accurate scientific assessment of a city’s evolutionary path.

“If you don’t think you have changed over time, look at your family photo album and see how much you have changed over the past 25 or so years. The same is true of the Earth,” said Darrel Williams, Landsat 7 Project Scientist.

Las Vegas is one of the fastest growing cities in the United States. Over a period of 27 years, a series of Landsat satellites has taken pictures to show how Las Vegas has changed from space.

The People’s Republic of China is one of the fastest growing economies in the world. As seen by Landsat, Shenzen, China practically transforms from a regional urban center to a metropolitan powerhouse in less than 10 years. Roads, bridges and massive construction projects transform the landscape. This massive growth alters lakes and mountains in the area, adding sediment and changing borders.

Tracking Devastating Floods and Fires

Following weeks of heavy rains in late Winter 2000, massive flooding inundated wide tracts of eastern and southern Africa, displacing more than 200,000 people. Vastly overflowing rivers sent much of that water rushing towards Mozambique, one of the hardest hit countries. Using images from Landsat, scientists were able to compare the size of rivers in Mozambique before, during and after the floods.

While fires tormented authorities and residents across the western United States in late summer of 2000, evidence of the disaster’s immense scale floated across the country. Heavy smoke and aerosols traveled as far east as the Great Lakes and was detected by Terra’s MODIS instrument.

Observing Massive Ice Sheets

Using Landsat 7 data, NASA glaciologist Bob Bindschadler saw a thin, 15-mile (25-kilometer) crack in the Pine Island glacier in Antarctica. “I was surprised that images taken just 10 months before showed no sign of such a fissure,” said Bindschadler. “A major break was forming in the Antarctic ice, and we caught it in the act. The growth of the crack has slowed. It may take as long as a year and a half for the iceberg to completely separate. We are learning more about iceberg formation as we continue to monitor the crack from space.”” said Bindschadler.

Monitoring Forest Health

Throughout much of the 1980s, deforestation in Brazil eliminated more than 15,000 square kilometers (9000 square miles) per year. That pace has only increased through the 90s and into the 21st century. Brazil is also home to more than a quarter of Earth’s tropical forests. Considering that the band of lush green that circles the globe through many equatorial nations is fundamental to the overall health of the whole planet’s environment, careful monitoring of forest health in the tropics is essential.

New Technologies and Techniques

NASA’s launch of the EO-1 spacecraft marked the beginning of NASA’s transition to a new way of doing business. “This mission could change the way we look at satellite technology, as well as change the way we look at the Earth,” said Dr. Bryant Cramer, New Millennium Program Manager. “EO-1 is testing and validating new technologies that will enable new or more cost-effective approaches to conducting science missions in the 21st century.”

If the technologies prove their promise, the new experimental satellite will blaze a trail for future, continued development of the Landsat data legacy. EO-1’s Advanced Land Imager, it’s Hyperion hyperspectral imager and the new Atmospheric Corrector all have direct application to providing next generation Landsat-type data.

Besides its use of advanced technology, Cramer says the EO-1 mission was significant for another reason; it signaled a revolutionary approach to mission operations.

For the first time ever, NASA is flying spacecraft in formation with other research satellites. In the first satellite maneuver of its kind, EO-1 is in an orbit just behind Landsat 7. This “formation flying” allows EO-1 to take a picture of the same scene as Landsat 7, only one minute later. This places the two spacecraft approximately 270 miles (450 kilometers) apart, plus or minus 30 miles (50 kilometers) or so. This affords scientists and engineers the opportunity to do some valuable tests. By flying the same route so close together, nearly identical images taken by each satellite can be compared on the ground.

In this carefully choreographed constellation, Landsat 7 takes the lead, followed by EO-1, SAC-C and finally Terra. The constellation of satellites provides unique research possibilities, including highly precise cross calibration of instruments.

For more information on this remarkable record of our planet’s changing landscape, go to: