The GOES-R Series: Next Generation of Geostationary U.S. Satellites

The Geostationary Operational Environmental Satellite-R Series (GOES-R) is the new generation of geostationary weather satellites. GOES-R is a collaborative program between NOAA and NASA. The GOES-R series is significantly improving the detection and observation of environmental phenomena that directly affect public safety, protection of property, and the economic health and prosperity of the U.S. The satellites are providing advanced imaging with increased spatial resolution and faster coverage for more accurate forecasts, real-time mapping of lightning activity, and improved monitoring of solar activity.

The GOES-R series is a four-satellite program (GOES-R/S/T/U) that will extend the availability of the operational GOES satellite system through 2036. GOES-R (renamed GOES-16 after launch) is the first in the series.  GOES-16 launched on November 19, 2016, and is now GOES-East.  GOES-S (renamed GOES-17 after launch), launched on March 1, 2017.  It is expected to transition to operations and become GOES-West in late 2018.

GOES satellites are in a geostationary orbit that provides nearly continuous observations of the Earth’s surface. GOES-17 is currently in the 89.5° W longitude checkout orbit, and GOES-16 is in its GOES-East operational location at 75° W longitude.

ABI Aerosol Measurements: Best of Both Worlds

GOES-R series satellites have six instruments; the most important instrument for aerosol measurements is the Advanced Baseline Imager (ABI). The ABI is a 16 channel imager with two visible channels, four near-infrared channels, and ten infrared channels. It provides three times more spectral information, four times the spatial resolution, and more than five times the temporal resolution than the previous generation GOES imager. ABI aerosol products include aerosol optical depth (AOD) and aerosol detection (e.g., smoke, dust masks).

The ABI combines the accuracy of multi-channel aerosol retrievals, like MODIS and VIIRS AOD, with the high temporal resolution (nearly continuous observations) of a geostationary satellite. As a result, ABI aerosol products are much more accurate than previous generation GOES imager products. Additionally, ABI products are available at 5-minute intervals, which can be tailored to 15-minute or 30-minute composites to fill the data gaps associated with clouds.

Aerosols are suspended particles in the atmosphere that scatter and absorb sunlight. When present in high concentrations, they are easily visible in satellite imagery. For routine detection and quantitative retrieval of aerosol amounts, the challenge is to separate the aerosols from clouds and bright surfaces. For ABI aerosol products, this separation is done by using measurements at different channels from the visible to thermal infrared. The 2.1 μm channel is transparent to most aerosols and is used to obtain the surface contribution to the satellite observed radiances over dark vegetated surfaces. A suite of infrared channels is used to detect clouds. Once a surface is characterized and cloudy pixels are identified, aerosols are retrieved through ABI measured radiances in the visible bands using pre-computed look-up tables. Qualitative information on the presence of aerosols can also be obtained using the brightness temperature difference between 11 μm and 12 μm and other spectral and spatial variability tests, especially for dust and smoke aerosols.

The ABI fire detection scheme uses the near infrared (3.9 μm) radiances to look for thermal signatures of fire referenced to the 11.2 μm thermal window, which accounts for the background surface. Fires and aerosol and trace gas emissions from the fires are currently derived from the legacy GOES imager measurements and the same algorithms have been adapted for the ABI. Emissions (aerosol and trace gas flux values) are estimated using linear regression models based on 3.9 μm band fire radiative power and emissions.

Applications of ABI Aerosol Products

AOD is an effective proxy for surface aerosol concentrations when aerosols are well mixed and uniformly distributed in the lower atmosphere. In this way, AOD from the GOES-R series ABI provides information on surface aerosol concentrations that can be used in air quality monitoring and forecasting applications. The aerosol detection product is qualitative; it indicates the presence of aerosol (dust and/or smoke) in a given pixel and can be used to quickly identify the location of dust and smoke plumes and as a mask in certain applications.

There are a variety of applications of ABI aerosol products. The use of the near real-time fire and smoke aerosol emissions in operational numerical air quality prediction models can greatly enhance the accuracy of forecast guidance. The combination of numerical forecast guidance and near real-time satellite aerosol imagery is benefiting operational forecasts of air quality and visibility. Accumulation of the satellite data over a long time period and extending the current GOES record is also useful for air quality assessment work done by U.S. EPA.