NASA - National Aeronautics and Space Administration

After a week of online voting, the results are in -- just in time for Earth Day. Choosing from 10 candidates for NASA's biggest accomplishment from its long history of Earth observations from space, voters selected precise global navigation made possible by NASA's pioneering research in Earth's rotation and shape as their top choice. Diagnosing Earth's ailing ozone layer and advancing weather forecasts were the second and third choices in the poll.

1. Finding Your Way with GPS (3280)
2. Diagnosing Our Ailing Ozone Layer (2408)
3. From Storm-Spotting to Next Week's Weather (2313)
4. Warming and Rising Seas (1443)
5. Global Reach of Air Pollution (1321)
6. Ice Sheets on the Move (1151)
7. It's a Big Green World (1102)
8. Predicting Feast or Famine (856)
9. A Lively Water World (631)
10. Ultimate Home Energy Audit (543)

The candidates were selected from a 2008 National Academy of Sciences study that cataloged the biggest achievements gained from five decades of observing Earth from space. NASA played a big part in these accomplishments that have changed our world.

Today NASA sponsors several programs aimed at precision navigation and positioning in Earth exploration, science and applications. In addition to providing the capability for precise navigation anywhere on Earth any time, scientists use supercharged GPS receivers to track movement across earthquake-prone faults, map water resources and melting glaciers. New positioning technologies such as GPS are fundamental to advances in exploration, science, industry, and society.

Below are descriptions of each of the NASA accomplishments included in the poll.

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> Larger image	From Storm-Spotting to Next Week's Weather Since the beginning of the space age, NASA has been at the forefront of using Earth orbit to get a better view of how weather systems develop. And now the world is a safer place to live in when it comes to dangerous weather. It has been decades since a hurricane or tropical cyclone has gone undetected before it struck land. NASA helped to build and launch an armada of orbiting sensors (more are in the works) that detect a growing number of factors that drive the world's weather. The result: seven-day forecasts have vastly improved over the past three decades. (Image: Hurricane Katrina, 2005, NASA's Tropical Rainfall Measuring Mission)
> Larger image	It's a Big Green World And now we can see it all -- green plants large and small, on land and on the sea, all over the globe. Ecology is now a truly worldwide undertaking, thanks to NASA's pioneering work in developing space-based instruments that can measure the greenness of chlorophyll in plants. We can track widespread changes in ecosystems, like the increasing growing season in the far north and the rise and fall of ocean algae and fisheries associated with El Nino events. And we can see how big a part ecosystems play in the ongoing cycling of carbon dioxide in and out of the atmosphere. (Image: From NASA's Sea-viewing Wide Field-of-view Sensor onboard the SeaStar spacecraft; NASA Goddard, the SeaWiFS Project, GeoEye)
> Larger image	The Global Reach of Air Pollution Air pollution was once thought of as just a local problem. But global views from space by NASA and other space agencies confirmed that pollution can move from country to country and even across oceans. In the 1980s the first maps of ozone pollution low in the atmosphere, where it is a health hazard, drew attention to human impacts on the atmosphere such as agricultural fires and land-use changes in the tropics. Newer satellite views show plumes of pollution crossing oceans. (Image: Alaskan wildfires, 2004; NASA's Terra, Moderate Resolution Imaging Spectroradiometer; Jacques Descloitres, NASA Goddard)
> Larger image	The Ultimate Home Energy Audit NASA led the way in building the Earth-orbiting tools to conduct the world's largest home energy audit: tracking the flow of energy into and out of the whole Earth system. With this big picture view, we've measured changes in the sun's energy output reaching Earth (pretty small) and the amount of energy redirected away from Earth after a massive volcano erupted into the stratosphere (a lot, but not for long). With this inventory of the natural factors that heat and cool the planet, we get a better fix on the role humans play in altering climate. (Image: Hurricane system cools Earth by reflecting sunlight (left, white/green areas) and warms it by trapping outgoing heat (right, blue/white); NASA's Aqua, Clouds and the Earth's Radiant Energy System instrument; NASA Langley)
> Larger image	Warming and Rising Seas It's a good thing NASA began keeping an eye on the temperature of the world's ocean surface in the 1970s. Without the continuous record of sea surface temperature since then by National Oceanic and Atmospheric Administration satellites (designed and launched by NASA), scientists would not have a key piece of evidence for global warming: most of the extra heat is absorbed in the oceans. And this isn't good news for rising sea levels -- water expands when it gets warmer, adding to rising seas around the world. (Image: Warm waters of the Gulf Stream, 2001; NASA's Terra, Moderate Resolution Imaging Spectroradiometer; Liam Gumley, University of Wisconsin-Madison)
> Larger image	Finding Your Way Behind the power of today's GPS units to get you where you need to go is a huge body of scientific knowledge about our spinning, shifting Earth. We live on an active planet where every piece of real estate moves relative to each other. Precise navigation with GPS satellites would be impossible without ultra-precise knowledge of Earth's shape and how it rotates. NASA pioneered much of this work with a global network of laser ranging satellites and super-charged GPS receivers to monitor daily changes in Earth’s surface. Oh, and there are side benefits like tracking the movement of tectonic faults, measuring sea level rise, and making air travel safer. (Image: NASA's Laser Geodynamics Satellite, LAGEOS I, launched 1976.)
> Larger image	Ice Sheets on the Move The massive polar ice sheets, a big piece of Earth's climate puzzle once too remote and forbidding for detailed study, have recently yielded a disturbing secret: they are shrinking. Satellite watchdogs from NASA, Europe and Canada have shown that they are losing massive amounts of ice at outlet glaciers. In addition, the floating ice shelves that buttress these glaciers are prone to failure. Many now see these changes as the "canary in the coal mine" of what global warming can do to Earth, including the possibility of a rapid rise in sea level. (Image: Antarctica's Larsen B Ice Shelf, 2002; NASA's Terra, Moderate Resolution Imaging Spectroradiometer; Ted Scambos, National Snow and Ice Data Center, University of Colorado)
> Larger image	Predicting Feast or Famine In the 1970s the U.S. Geological Survey and NASA developed a satellite instrument that could pick out different types of large-scale agricultural crops and map their location. Scientists used this tool to estimate the size of annual yields of wheat, corn, soybeans, and other crops, providing a new way to forecast food shortages (and surpluses) around the world. Federal agencies now routinely use satellite imagery from NASA and others in crop commodity forecasting of all major grains. (Image: Crop circles in Kansas, 2001; NASA's Terra, Advanced Spaceborne Thermal Emission and Reflection Radiometer; NASA Goddard, METI, ERSDAC, JAROS, U.S./Japan ASTER Science Team)
> Larger image	A Lively Water World Scientists had only a fuzzy picture of the world's changing oceans before NASA joined forces with the French Space Agency to measure the height of the sea surface from space.  The new satellites uncovered a topsy-turvy water world full of tiny eddies that mix and churn and the grand-daddy of all ocean phenomena: El Nino. This big-time ocean event -- lasting more than a year and stretching halfway around the world -- changes weather and climate across the globe.  The view from space revealed a dynamic ocean that shapes our climate and a rise in sea level three times faster than a century ago. (Image: High and low areas of the world's oceans (red and blue, respectively), 2009; Jason-1 and Ocean Surface Topography Mission on Jason-2; NASA Jet Propulsion Laboratory, CNES, CLS, DUACS)
> Larger image	Diagnosing Our Ailing Ozone Layer NASA satellites and aircraft provided critical evidence in the international diagnosis of Earth’s ozone layer. With scientific proof of how certain manmade chemicals were destroying the protective ozone layer high in the stratosphere, the nations of the world acted to ban the culprits. Scientists now so thoroughly understand the ingredients of the chemical brew and the atmospheric conditions producing ozone damage that they can predict when the ozone hole over Antarctica will recover (look for it around 2070). (Image: Ozone hole over Antarctica, 2007; NASA's Aura, Ozone Monitoring Instrument)

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