Across four decades since 1972, Landsat satellites have continuously acquired space-based images of the Earth’s land surface, coastal shallows, and coral reefs. The Landsat Program, a joint effort of the U.S. Geological Survey (USGS) and the National Aeronautics and Space Administration (NASA), was established to routinely gather land imagery from space. The result of this program is a long-term record of natural and human induced changes on the global landscape.
Each Landsat satellite images the Earth’s surface along the satellite’s ground track in a 185 kilometer-wide (115 mile-wide) swath as the satellite moves in a descending orbit (moving from north to south) over the sunlit side of the Earth. Each satellite crosses every point on the Earth at nearly the same time once every 16 or 18 days, depending on its altitude. Landsats 1, 2, and 3 orbited at an altitude of 920 kilometers (572 miles), circling the Earth every 103 minutes yielding repeat coverage every 18 days. Landsats 4, 5, and 7 were placed in orbit at 705 kilometers (438 miles) altitude, circling the Earth every 99 minutes, for a 16-day repeat cycle.
The Landsat Data Continuity Mission (LDCM) is the next-generation Landsat satellite and is expected to be launched no earlier than February 11, 2013. This mission will ensure the continued acquisition and availability of Landsat-like data well beyond the duration of the current Landsat 5 and Landsat 7
The Landsat satellites have a spectral band range from visible green to near-infared. As to why the colours can seem a little funky in the images, check out this fantastic presentation that discusses how Landsat images are made and the important distinction between photographs and images, especially when it concerns satellite imagery.