Landsat

Landsat 8 carries two push-broom instruments: the Operational Land Imager (OLI), and the Thermal Infrared Sensor (TIRS).
The Landsat Program is a series of Earth-observing satellite missions jointly managed by NASA and the U.S. Geological Survey.
National Land Imaging (NLI) was an interagency effort (begun in 2006) to develop a long-term plan to achieve technical, financial, and managerial stability for operational land imaging.
Remote sensing is the process of detecting and monitoring the physical characteristics of an area by measuring its reflected and emitted radiation at a distance from the targeted area.
Simply defined, scale can be expressed as the ratio or proportion between a distance on the aerial photographs (or maps) and the actual distance on the ground or land surface.
This massive database updates our knowledge of the Nation’s land cover and documents precisely where land cover change has occurred between 2001 and 2006.
For many locations outside the U.S., there may be scenes that were collected by the sensor but the data is not archived or distributed by the USGS.