Remote sensing, in simplest terms, means viewing something from a distance rather than by direct contact. A handheld camera is an example of a remote sensing instrument. In terms of earth science, remote sensing refers to the ability of satellites to detect electromagnetic radiation from features on the earth's surface or in the atmosphere. Solar energy that reaches the earth is composed of many kinds of radiation, including light that is visible to people, thermal infrared, microwave, radar, and X-rays. Every substance with a temperature greater than absolute zero (-273 degrees Celsius, or -459 degrees Fahrenheit) emits some form of electromagnetic radiation. Some satellite sensors detect visible light reflected from the earth's surface or atmosphere, and others detect radiation emitted from the earth.

Image courtesy of NASA.

Satellites can easily measure sea ice in the visible, infrared, and microwave regions of the electromagnetic spectrum. However, there are advantages and disadvantages to each type of radiation. None of the spectral regions allow scientists to optimally view sea ice in all conditions. The following sections describe each region in more detail.

Remote Sensing Links

The following Web sites provide more detailed information about remote sensing and its applications:

Fundamentals of Remote Sensing: Tutorial aimed at high school and university students provided by the Natural Resources Canada.
Remote Sensing Tutorial: Provided by NASA.
Measuring the Electromagnetic Spectrum: Explained by NASA's Goddard Space Flight Center.
Remote Sensing: Introduction and historical account by NASA's Earth Observatory.