Definitions for "Thermal infrared"
The preferred term for the middle wavelength ranges of the infrared region extending roughly from 3 µm at the end of the near infrared, to about 15 or 20 m where the far infrared commences. In practice the limits represent the the envelope of energy emitted by the Earth behaving as a graybody with a surface temperature around 290 K. Seen from space, the radiance envelope has several brighter bands corresponding to windows in the atmospheric absorption bands. The thermal band most used in remote sensing extends from 8 to 15 µm.
The middle and far infrared portions of the spectrum; mainly used to distinguish infrared radiation of terrestrial origin from the solar infrared.
Electromagnetic radiation with wavelengths between 3 and 25 micrometers. [NOAA