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University of Nebraska–Lincoln

The molecules of the atmosphere absorb solar radiation. Each molecule type has its own particular radiation wavelength that it will absorb. This absorbed radiation is retained as internal energy or re-emitted in other wavelengths.

Ozone, water vapor, carbon dioxide, and methane gases are the primary absorbers of energy. Oxygen and nitrogen, the most abundant gases in the atmosphere, are the least absorbing.

Energy wavelengths shorter than0.3m (X-rays and gamma rays) are completely absorbed by the ozone layer in the upper atmosphere. Most of the ultraviolet rays are also absorbed. Only microwaves and longer wavelengths are able to penetrate the atmosphere with little absorption.

Visible light rays and infrared wavelengths are generally transmitted through the atmosphere. Wavelength regions, where the waves are relatively uninterrupted in their path, are called "atmospheric windows." These are the regions of the spectrum where remote sensing data can be acquired.

The spaces between the atmospheric windows, called "absorption bands," are shown in the figure above, along with the gases mainly responsible for atmospheric absorption. Ozone absorption cuts off at 0.29m and also appears weakly in the visible part of the spectrum. Infrared absorption is caused primarily by water vapor and carbon dioxide.

The sensors onboard the various satellites (GOES, AVHRR, Landsat) used for remote sensing take advantage of the atmospheric windows. Each satellite has a particular set of from five to seven sensors. Each of the sensors records data from a specific wavelength range known as a "band."