With an archive of almost 30 years of remote Earth observations, NASA has opened grand vistas for research in many areas of study. NASA's global observations, preserved for long-term comparisons of change over time, have allowed scientists to gain a better understanding about how the atmosphere, land, oceans and life work together systemically.
In conjunction with Earth Day in late April, NASA released a new collection of images of Earth, derived from sophisticated research hardware on orbit.
In 1972, with the launch of the first Landsat satellite, the legacy of remote sensing began in earnest. Six more followed, with the latest, Landsat 7, rocketing into space in April 1999.
Eight months after Landsat 7's launch, NASA launched Terra, the flagship in its series of Earth Observing System spacecraft. This multi-national satellite is enabling researchers to pursue some of the grandest and most complex questions about our home planet, including unprecedented research on climate change.
In November 2000, NASA added the latest in this long line of remote sensing spacecraft when it launched the technology pathfinder, EO-1.
From Landsat 1 to EO-1, these powerful and sophisticated satellites offer high-resolution images of Earth. 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 growthWhen a city grows, buildings and roads are not the only things that 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 vital 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, a scientist with the Landsat 7 project.
Tracking devastating floodsFollowing 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.
Observing massive ice sheetsUsing Landsat 7 data, NASA glaciologist Bob Bindschadler saw a thin, 15-mile crack in the Pine Island glacier in Antarctica. "I was surprised that images taken just ten 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," he said.