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Fall 2007 Vol. 7 No. 3

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50 Years in the Sky

A Satellite Success StoryŠImage Club/Getty Images

Fifty years ago scientists from dozens of countries embarked on International Geophysical Year research expeditions to collect and share data on various planetary phenomena. But it was the Soviet Union's launch of Sputnik that would forever change the way scientists observe the planet. Even then, researchers knew that no matter how far they ventured on ground or by sea, they could never achieve the observational vantage point that satellites were sure to provide.

Indeed, the ability for humanity to see Earth from space was akin to looking at oneself in the mirror for the first time, notes a new National Research Council report that catalogs many of the scientific achievements -- and corresponding benefits to society -- made possible by the first five decades of the satellite age.

The scientific accomplishment probably most appreciated by the general public is the ability to watch the weather in motion. These weather movies are made possible by "geostationary" satellites that stay over the same point on the equator, taking frequent images from the same vantage point. Geostationary satellites were first launched in the 1960s, and since then, no hurricane anywhere in the world has gone undetected.

Satellites also have been invaluable to climate science. The radiometer aboard Explorer 7, a U.S. satellite in orbit from 1959-1961, provided the first direct measurements of energy entering and leaving Earth. As satellite radiometers improved, fluctuations in this energy "budget" could be measured and linked to particles from volcanic eruptions or atmospheric greenhouse gases, concentrations of which also could be detected. Data from satellites also provided an important record of global ocean and air temperatures, and led to new revelations of ice sheet flow. And it was only because of frequent satellite coverage that the world was able to watch 2,000 square kilometers of an Antarctic ice shelf disintegrate in just two days during 2002.

The report highlights many other scientific triumphs made possible by these eyes in the sky, and how society took advantage of them. Satellites confirmed the extent of ozone depletion above the poles, for instance, which led to the Montreal Protocol banning ozone-destroying chemicals. Images of land-cover changes allowed for the establishment of the Famine Early Warning Systems Network. Satellites also allow geographical positions to be pinpointed with centimeter accuracy, making GPS a part of everyday life.

The report also echoes concerns raised in earlier Research Council studies that current delays and cancellations in U.S. satellite missions are a setback for science.   -- Bill Kearney

Earth Observations From Space: The First 50 Years of Scientific Achievements. Committee on Scientific Accomplishments of Earth Observations From Space, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies (2007, approx. 200 pp.; ISBN 0-309-11095-5; available from the National Academies Press, tel. 1-800-624-6242; $44.50 plus $4.50 shipping for single copies).

The committee was chaired by Jean-Bernard Minster, professor of geophysics, Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California, San Diego. The study was funded by NASA.

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Copyright 2007 by the National Academy of Sciences