On a warm July day in 1972, NASA launched the Earth Resources Technology Satellite, a new Earth-imaging satellite. “ERTS” was the first satellite of what later became NASA and the U.S. Geological Survey’s Landsat Program, an ambitious effort with a goal of documenting the entirety of Earth from space. The first Landsat was so successful it sparked a series of satellites that have created the longest contiguous record of Earth’s surface from a space-eye view. In fact, it continues growing to this day, 50 years later.
“The early Landsats revolutionized the way we observed the Earth from space,” said Jim Irons, director emeritus of the Earth Sciences Division at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Since it started, Landsat has amassed over 10 million images. These images, also called scenes, show current snapshots of land and coasts. However, when paired with images of years past, they also reveal changes through time. This includes glaciers slowly disappearing and urban spaces sprawling across the landscape.
These scenes and time series have a wide range of useful applications around the globe: Ecologists use them to determine the extent of deforestation; hydrologists use them to track how rivers change; farmers and agricultural organizations use them to analyze crop health.