Satellite imaging and sensing is the process by which the electromagnetic energy reflected or emitted from the Earth surface is captured by a sensor located on a spaceborne platform. The Sun as well as all terrestrial objects can be sources of energy. All objects give off radiation at all wavelengths, but the emitted energy varies with the wavelength and with the temperature of the object. A “blackbody” is an ideal object that absorbs and reemits all incident energy, without reflecting any. If one assumes that the Sun and the Earth behave like blackbodies, then according to the Stefan–Boltzmann law, their total radiant exitance is proportional to the fourth power of their temperature. The design of new satellite instruments is based on the principle that targets of interest can be identified based on their spectral characteristics.