The Landsat 7 satellite flew its 50,000th orbit on Monday, September 8, 2008. Landsat 7 has been orbiting the Earth since its launch in April 1999. Landsat satellites provide an unparalleled record of Earth’s varying landscapes to help us understand how Earth is changing and what those changes mean for life on our planet. The consistency of Landsat’s data from sensor to sensor and year to year, makes it possible to trace land cover changes from 1972 to the present. Landsat sensors have captured over two million digital images of Earth’s continents and surrounding coastal regions. NASA designs the Landsat Earth-observing satellites; USGS manages the satellites, archives the imagery, and makes the data available to all interested users.
Safeguarding freshwater resources is crucial, and while scientists use a variety of ground-based techniques to gauge water quality, the Landsat program has provided water quality data from orbit for decades.