GOES West (GOES 17)

Like GOES-East, of the six instruments on GOES-West used for observing the earth and sun, it is the "Advanced Baseline Imager" (ABI) instrument that provides visible and infrared views the earth. The ABI produces images at 16 different wavelengths (called bands and/or channels).

Note: During post-launch testing of GOES-West an issue with a cooling system was discovered. The loop heat pipe subsystem, which transfers heat from the ABI electronics to the radiator for cooling, is not operating at its designed capacity.

The consequence of this is inadequate cooling for some of the infrared (IR) channels on the instrument during parts of the night, leading to partial loss of ABI imagery.

During nighttime hours, for part of the year, the sun shines onto the ABI detectors which heats up faster than they can be cooled. The detectors become warmer than they're designed to operate and emissions from the Earth result in overwhelming some infrared channels, meaning a useful signal is not available.

The individual channels are as follows:

Visible Bands

There are two visible bands, blue and red. These two wavelengths are named relative to their location on the visible portion of the electromagnetic spectrum.

While in their natural state these images would appear in blue and red hues respectfully, colors have been desaturated to appear in grayscale. Since these are "visible" channels the images will appear black at night.

Near-Infrared Bands

Channel 3: The "Veggie" band

Although this is a "near-infrared" band (not visible to the eye) vegetation is readily seen at this wavelength and therefore given the nickname "veggie" band. It is useful in assessing land characteristics when determining fire and flood potential. For example, forest fire damage will appear darker as compared to nearby unaffected areas. This helps pinpoint areas where significant rainfall may lead to flooding and mudslides.

Water is very absorbing at this wavelength which makes it appear dark. So, there is a high contrast between land and water. Channel 3 is also used to simulate a "green" band needed to produce a red-green-blue (RBG) color image.

Water Vapor Bands

The satellites do not directly detect moisture but actually detect temperature. Water vapor (water in a gaseous state) absorbs radiation at these particular frequencies. When much radiation has been absorbed by water vapor the satellite does not sense much radiation and therefore records a low temperature.

The satellite interprets a low temperature as high water vapor content. When much radiation is received by the satellite, it senses a high temperature and consequently a low amount of water vapor.

As a result, the depth at which the satellite peers into the atmosphere will vary with amount of moisture over any particular point from day to day.

Channel 8: The "Upper-Level" Water Vapor band

At present this band provides information about the dynamics of the atmosphere near the tropopause (the boundary between the troposphere below - where we live - and the stratosphere above). In the future, this channel, along with other infrared channels and weather model information, will provide the amount of ozone in a column. The Total Ozone product is expected to provide information to forecasters that will help them forecast areas of atmospheric turbulence and to provide better forecasts of air quality.

This image is not a single channel but a combination of several GOES-R channels along with a polar orbiting satellite. During daytime, bands 1, 2 and 3 (red, blue and "veggie") are combined to produce an approximation of how it would appear if viewed with human eyes from space.

At night, bands 7 and 13 are combined and colorized. The nighttime blue colors represent liquid water clouds such as fog and stratus, while gray to white indicate higher ice clouds. Finally, from a polar orbiting NASA satellite, the nighttime city lights are added.