Forty years ago today, NASA launched the first Landsat satellite from Vandenberg Air Force Base in California.
"It was the granddaddy of them all, as far as starting the trend of repetitive, calibrated observations of the Earth at a spatial resolution where one can detect man's interaction with the environment," Dr. Darrel Williams, a Landsat 7 Project Scientist.
The Landsat Project is now made up of a series of newer satellites and the data are used to track detailed changes on Earth. Scientists can look at how land-use has changed from population growth or use the data to see damage from natural disasters, such as Hurricane Katrina and the tsunami in Japan.
Landsat can take amazingly detailed images of the Earth's surface. Check out the below image of Tucson taken in 2001.
NASA is preparing to launch the newest Landsat satellite in February of 2013.