The Landsat program is the longest running satellite imagery program on Earth. The first satellite was launched on July 23rd 1972 and the most recent launch was February 11th 2013. With Landsat 9 to be launched in 2020.
The instruments on the Landsat satellites have acquired millions of images. The images, archived in the United States and receiving stations around the world, are a unique resource for global change research and applications in agriculture, cartography, geology, forestry, regional planning, surveillance and education, and can be viewed through the U.S. Geological Survey (USGS) ‘EarthExplorer’ website. Landsat images are usually divided into scenes for easy downloading.