Landsat Missions
In the past, the U.S. Geological Survey (USGS) and NASA collaborated on the creation of three global land data sets from Landsat images: one from the 1970s, and one each from circa 1990 and 2000. Each of these global data sets was created from the primary Landsat sensor in use at the time: the Multispectral Scanner (MSS) in the 1970s, the Thematic Mapper (TM) in 1990, and Enhanced Thematic Mapper Plus (ETM+) in 2000.
To extend this multi-decadal Landsat data collection, NASA and the USGS have again partnered to develop the Global Land Survey 2005 (GLS 2005), a new global land data set with core acquisition dates of 2005-2006. The data will consist of both Landsat TM and ETM+ imagery, making GLS 2005 the first-ever global data set built with data from two sensors.
While Landsat 7 ETM+ data can be acquired around the globe, stored on the spacecraft, and downlinked at USGS EROS, Landsat 5 TM data must be downlinked in real time to a local ground station (and cannot be stored for downlink at USGS EROS). To obtain Landsat 5 TM images for areas outside of the United States, the USGS negotiated agreements with international ground stations to downlink and send data to USGS EROS. These agreements make thousands of additional Landsat 5 TM scenes available for GLS 2005 consideration.
The USGS Landsat Ground Station archives nearly 100,000 new Landsat 7 ETM+ images every year. These images are a record of nearly all of the land area on Earth. ETM+ scenes have a 22 percent data loss due to the Scan-Line Corrector failure in 2003. This requires combining two ETM+ scenes for each path/row to have complete, or near-complete, coverage.
The Landsat 7 ETM+ and Landsat 5 TM data incorporated into the GLS 2005 data set must meet quality and cloud cover standards. Data recorded in 2004 and 2007 will be used as needed to fill areas of low image quality or excessive cloud cover.
GLS 2005 data is scene-based, and can be searched and downloaded from Glovis or EarthExplorer.
U.S. Department of the Interior |
U.S. Geological Survey
URL: http://landsat.usgs.gov
Page Contact Information: landsat@usgs.gov
Page Last Modified: August 24, 2009
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