Remote Sensing: Infrared

VIIRS false-color image of the Arctic Ocean
Daily infrared images of the polar regions, captured by the VIIRS sensor, are available from NASA Worldview. Compared to visible imagery—showing what appears to human eyes—infrared imagery can better distinguish between ice and snow (turquoise), and clouds (nearly white).

Satellite sensors that measure infrared radiation infer the amount of heat emitted from the Earth. Objects with an average Earth temperature (roughly -50 to 50 degrees Celsius, or -58 to 122 degrees Fahrenheit) emit most of their energy in the infrared region.

Infrared sensors can easily detect sea ice because its temperature is generally much colder than the surrounding ocean. A typical winter sea ice temperature is -20 to -40 degrees Celsius (-4 to -40 degrees Fahrenheit), while the surrounding ocean temperature is at least just above freezing. Limitations in measuring infrared radiation from space include the following:

  • Because clouds also emit and reflect infrared radiation, clouds prevent satellites from detecting infrared radiation from sea ice.
  • Sea ice melts during the summer, and the surface temperature increases to the freezing point. Melting sea ice is difficult to distinguish from surrounding ocean that is also near the freezing point.
  • Sea ice that is just forming and is very thin has a temperature very close to freezing and thus can be hard to distinguish from the surrounding ocean.

The following satellites and sensors observe infrared radiation.

Last updated: 3 April 2020