True-Color Imagery from GOES—A Synopsis of Past and Present

The human eye is sensitive to three primary bands of light—centered on the red, green, and blue parts of the visible spectrum. The human eye is not very sensitive to variations in shades of gray—being able to distinguish only approximately 25 different gradations of gray in satellite images. However, by using the three different color sensors, the eye has the potential to distinguish up to a million different values of color. Hence, color is a powerful tool for distinguishing various objects of interest with subtle intensity variations. The Geostationary Operational Environmental Satellites-R (GOES-R) series of geostationary satellites do not have a green channel. However, a synthetic green channel can be constructed from the blue, red, and nearinfrared “veggie” channels for the use in a true-color visible image. Since the launch of the GOES-16 satellite, several different groups have developed color visible algorithms that are available on public websites. The purpose of this paper is to help explain the similarities and differences of true-color GOES images that are on the web and in other locations.