Landsat 7, launched on April 15, 1999, continues the legacy of Earth observations started by Landsat 1 in 1972. Since then, Landsat satellites have been observing the Earth's continental and coastal landscapes at a scale where human impacts and natural changes can be monitored, differentiated, and characterized over time.
NASA and the Department of the Interior’s U.S. Geological Survey (USGS) work together on Landsat 7. NASA was responsible for building and launching the satellite and its sensors. Following an initial in-orbit check out period, USGS assumed responsibility for satellite operations and for collecting, archiving and distributing data.
The Landsat data archived, preserved, and distributed by USGS constitute the longest continuous record of the global land surface as seen from space. Landsat data are critically important for understanding and managing forests and farms, mitigating the effects of wild fires, studying changes in urban landscapes, measuring the extent of flood and storm damage, examining wildlife habitat, measuring glacial retreat, mapping the extent of the Antarctic ice sheet, and much more. Landsat data have become a part of our nation’s infrastructure, and the data record constitutes a priceless archive that is open and freely available to everyone, everywhere.
The Earth observing instrument on Landsat 7, the Enhanced Thematic Mapper Plus (ETM+), advances the capabilities of the highly successful Thematic Mapper instruments on Landsats 4 and 5. (Landsat 5, launched in 1984, remained in operation until early 2013.) The Landsat 7 ETM+ is a highly accurate, calibrated sensor and its data have served as a standard for the calibration and validation of observations from a number of other Earth-observing sensors.
The Landsat 7 mission performed flawlessly until May 2003, when a component of the ETM+ optical scanning system (called the scan line corrector or “SLC”) failed, leaving wedge-shaped spaces of missing data on either side of the images. Six weeks later the ETM+ resumed its global land survey mission, resulting in only a short suspension of its imagery acquisitions for the U.S. archive. The USGS continues to collect, archive, and distribute ETM+ data, which remain accurate with respect to radiometry and geolocation. Many users find the images useful despite the wedge-shaped gaps and 25% loss of data per image.
The following Landsat mission, Landsat 8, launched on Feb. 11, 2013.