This is a very brief description of the Landsat sensors. Users are encouraged to review sensor information before working with these data. A few suggested sites are the USGS Landsat Program site and the NASA Landsat Users Handbook.
Basic Image Characteristics
There are four generations of sensors used in the Landsat program. The Multi Spectral Scanner (MSS) mission ran from 1972 to 1993 and had four spectral channel covering the green, red, and (2) near infrared channels. The spatial resolution was 57 or 60 meters.
The Landsat Thematic Mapper (TM) mission began in the mid-80’s and Landsat 5 finally ended November 2012. This sensor features seven spectral channels at 30 meters spatial resolution.
The Landsat 7 Enhanced Thematic Mapper (ETM) mission began in 1999 and is still operational. It features the same spectral channels as the TM sensor, with the addition of a second thermal channel and a 15 meter panchromatic channel. On May 31, 2003 the ETM scan line corrector failed and ETM images since that time are missing large portions each scene. On USGS sites these images are designated as SLC-Off and use of these images is generally not recommended.
The Landsat 8 mission began in the spring of 2013. This features 11 bands of data, many similar to the ETM mission. The primary file in the Optical Land Imager (OLI) sensor has 7 bands of data at 30m resolution; Coastal Blue, Blue, Green, Red, NIR, SWIR1 and SWIR2. It also has a 30m Cirrrus file and a 15m Panchromatic file. The Thermal InfraRed (TIR) sensor has 2 bands of data with 100m resolution. Users are advised to only use the first (band 10) TIR band in their research.
Landsat 8 Pre-WRS-2
The Landsat 8 program began acquiring images in March of 2013 once the final sensor calibration checkout was completed . This was before the satellite actually arrived at its final orbital position on April 11, 2013. As a result, these scenes do not properly align to the designated Path/Row footprint and each cell covers a slightly smaller area. These scenes are identified as Pre-WRS-2 and we do not recommend using these for studies over time.
Worldwide Reference System
The Worldwide Reference System (WRS) is used to identify the path and row of each Landsat image. The path is the descending orbit of the satellite. Each path is segmented into 119 rows, from north to south. The Landsat MSS sensor had a swath width of 180 km and global coverage required 251 paths. The Landsat TM, ETM and OLI sensors have a swath width of 185 km and require only 233 paths for complete coverage. MSS and TM scenes share common rows, but in most cases the paths will be different. Because of this difference, MSS scenes are identified using WRS I while TM, ETM and OLI scenes use WRS II path/row designations. The data archive section of the CEO web site uses the WRS II designation for all path/row images.