Remote sensing means observing something from a distance. Satellites observe the Earth from space and help scientists study large tracts of land and how that land changes over time.

The sensors onboard the Landsat satellites use reflected light to detect electromagnetic energy on the Earth’s surface. The level of energy is represented by the electromagnetic spectrum, which is the range of energy that comes from the Sun. The light from the Sun that we can see is only a small part of the electromagnetic spectrum and includes the colors of the rainbow. Satellite sensors record this information in different portions of the electromagnetic spectrum, which is measured in wavelengths. Landsat satellite sensors detect both visible and infrared light.

When satellite images are made, these “invisible” types of light are assigned visible colors to represent them so that our eyes can see the data.