TABLE 2.1 Landsat Satellite Characteristics
|System||Sensors||Radiometric Resolution||Temporal Resolution||Orbit Altitude||Launch Date||Decommission or Expiration Date|
|Landsat 1 (ERTS-A)||July 23, 1972||January 6, 1978|
|Landsat 2 (ERTS-B)||RBV and MSS||6 bits||18 days||900 km||January 22, 1975||February 5, 1982|
|Landsat 3||March 5, 1978||March 31, 1983|
|Landsat 4||July 16, 1982||June 15, 2001|
|MSS and TM||8 bits||16 days||705 km||TM: November 2011|
|Landsat 5||March 1, 1984||MSS: January 6, 2013|
|Landsat 6||ETM||8 bits||16 days||705 km||Launch failed October 5, 1993|
|Landsat 7||ETM+||8 bits||16 days||705 km||April 15, 1999|
|Landsat 8 (LDCM)||OLI and TIRS||12 bits||16 days||705 km||February 11, 2013|
NOTE: ETM, Enhanced Thematic Mapper; MSS, Multispectral Scanning System; OLI, Operational Land Imager; RBV, Return Beam Vidicon; TIRS, Thermal Infrared Sensor; TM, Thematic Mapper.
SOURCE: NASA Goddard Space Flight Center, see http://landsat.gsfc.nasa.gov.
user surveys have shown that Landsat data at moderate resolutions (15 to 100 m, at 8-to 16-day frequency) have significant intrinsic value for a broad range of federal and nonfederal scientific and operational uses but little promise for commercialization.
Spurred by photographs of Earth from the Apollo missions in the 1960s, the Department of the Interior and the U.S. Department of Agriculture (USDA) envisioned a program to provide unclassified remotely sensed data in support of resource studies and planning.5 NASA launched the first Earth Resources Technology Satellite (ERTS) (subsequently renamed Landsat 1) in July 1972, and since then a total of seven successful missions have collected more than 2 million images of Earth spanning a 40-year period. While the technology used to capture Landsat data has evolved over its 40-year life span, each new Landsat system has been designed so that many of the imagery products are backward compatible. More important than each system’s innovation and science is the Landsat suite’s combined continuity of observations, which bring overwhelming value to each new Landsat system.
Tables 2.1 and 2.2 summarize the technical characteristics of the seven successful Landsat systems in the common categories of spectral, radiometric, spatial, and temporal resolutions. All systems have had the same swath width, 185 km. Over the span of the Landsat systems, spectral resolution has increased from 4 to 11 bands, with some changes in the shape of the spectral response functions, and the spatial resolution of those bands has narrowed from 80 to 15, 30, and 100 m.6 Radiometric resolution has increased from 6 bits on Landsats 1 through 3, to 8 bits on Landsats 4 through 7, and to 12 bits on Landsat 8. Landsats 1 through 3 had an 18-day repeat cycle, which was shortened to 16 days on subsequent missions. Temporal resolution has sporadically increased from a 16-day revisit to an 8-day revisit only when and where two Landsat systems were operating simultaneously, which has, unfortunately, been rare over the past 20 years because of Landsat 5’s inability to store data onboard and Landsat 7’s scan line corrector failure in 2003.
While unique, Landsat is only one of many multispectral Earth observing sensing systems. Commercial providers such as DigitalGlobe, Inc.,7 offer finer-spatial-resolution multispectral imagery for sale, but it is costly
5 D.T. Lauer, S.A. Morain, and V.V. Salomanson, The Landsat program: Its origins, evolution, and impacts, Photogrammetric Engineering and Remote Sensing 63:821-838, 1997.
6 Spatial resolution refers to the distance between distinguishable features in an image, whereas the pixel size in images delivered is often –resampled. Note that the spatial resolution of the thermal band decreased from 120 to 60 m with Landsat 7, but reverted to 100 m on Landsat 8.
7 DigitalGlobe acquired GeoEye in January 2013.