More than two thousand satellites are currently in orbit. They measure the earth's surface characteristics, ocean currents, clouds and the gaseous content of the atmosphere. One of the oldest programs is Landsat. Run by both the National Aeronautics and Space Administration (NASA) and the United States Geological Survey (USGS), Landsat is still widely used today because it provides its data to researchers free of charge.read more

Original article is at http://earthtrends.wri.org/updates/node/332
This article was gathered from EarthTrends - News
Posted by Editors on December 23, 2008
Link to this article:
http://www.blueglo.be/2008/12/observing_earth_from_space_lan.html