LANDSAT Satellites

The Landsat Program is a series of Earth-observing satellite missions (seven to date) jointly managed by NASA and the U.S. Geological Survey.  The Landsat Program is the longest running operation in the collection of multispectral, digital data of the earth’s surface from space. It has operated continuously since the first satellite was launched in 1972. All of the images that have been acquired from the program are stored at the National Satellite Land Remote Sensing Data Archive, EROS Data Center, Sioux Falls, SD. These images enable people to study and evaluate the changes in the Earth’s landscape caused by natural processes and human practices.

The primary satellite images used in this METRIC™ project are from Landsat 5 (launch date 1984) and Landsat 7 (launch date 1999). These satellites operate in space in a circular, sun-synchronous, near-polar orbit.  On each day-side pass, they scan the ground with a swath width of 185 km (about 115 miles).  They orbit the earth at an altitude of approximately 705 km (about 438 miles); traveling speed is 4 miles per second, with a repeat cycle of 16 days. The Landsat 5 satellite has a Thermatic Mapper (TM) instruments and the Landsat 7 satellite has an enhanced Thermatic Mapper (ETM+). Landsat 5 takes images on a 30-meter resolution, multispectral (6 bands) band and a 120-meter resolution thermal band.  Landsat 7 also takes images on a 30-meter resolution, multispectral (6 bands) band, a 60-meter resolution thermal band and a 15-meter panchromatic band. Images are approximately 185 km (about 115 miles) wide and 170 km (about 106 miles) long.

Both satellites have had problems. Landsat 5 had to have its Multispectral Scanner System (MSS) turned off and problems with the solar array caused operations to be suspended for a short period of time until a new method to fix this problem was devised. 

Landsat 7 has lost its scan line corrector (SLC) which impacts the imagery the satellite produces.  Without this system, the EMT+ acquires approximately 75 percent of the data for any given scene.  To help correct the SLC-off data gaps, data from multiple acquisitions are being merged.  But overall, both satellites have gone beyond their normal life expectancy and have preformed well.  Landsat 5 has been operational for over 24 years and Landsat 7 has been operational for over nine years.  Both satellites are expected to be retired in 2010 – 2011.  Landsat 8 is on the drawing boards and is expected to launch in 2011 -2012.

Landsat 7 Satellite