The GASP product is a retrieval of the Aerosol Optical Depth (AOD) made from the current GOES WEST visible imagery.

Conus Images

(4km resolution) See below for image descriptions.

Time (UTC)	GOES AOD	Time (UTC)	GOES AOD
Latest	JPG	12:45	JPG
13:15	JPG	13:45	JPG
14:15	JPG	14:45	JPG
15:00	JPG	15:30	JPG
16:15	JPG	16:45	JPG
17:15	JPG	17:45	JPG
18:30	JPG	18:45	JPG
19:15	JPG	19:45	JPG
20:15	JPG	20:45	JPG
21:00	JPG	21:30	JPG
22:15	JPG	22:45	JPG
23:15	JPG	23:45	JPG
00:30	JPG	00:45	JPG
01:15	JPG	01:45	JPG
02:15	JPG	02:45	JPG
03:00	JPG	03:30	JPG

Animated Image Loop

The latest GASP product can also be viewed through the GASP Internet Map Server.

Imagery Description

• Time (UTC)
• EST = UTC -5, CST = UTC - 6, MST = UTC - 7, PST = UTC - 8
• Latest Image
• The latest GOES image available to the processing system.
• Aerosol Optical Depth (from latest image and most recent surface reflectance retrieval)
• Color scale represents the aerosol optical depth.
• The gray scale in the sunlit portion of the image represents the reflectance of either clouds, sun glint or regions where the retrieval is insensitive to aerosol (e.g., over bright surfaces)
• The thick black line is where the solar zenith angle is 80 degrees.
• The retrieval is not performed at solar zenith angles above 80, so the visible reflectance is provided between 80 and 89 degrees
• Beyond 89 degrees, the IR data (from channel 4) is shown to provide a continuous image.

Method Summary

• A clear sky composite reflectance (background) image is created by selecting the second darkest pixel from the previous 28 days for each observation time.
• The surface reflectance is obtained from the composite background image, using look-up tables calculated with the 6S Radiative Transfer model.
• The Aerosol Optical Depth is estimated using look-up tables from the 6S Radiative Transfer model and the calculated surface reflectance.
• Radiative Transfer calculations assume a continental aerosol model and Lambertian surface.
• Clouds are identified using spatial and spectral tests similar to those developed for CLAVR (Clouds from AVHRR). The AOD is shown only for cloud free pixels.

GASP Team:

Scientists: Shobha Kondragunta, NESDIS/STAR (Originally Ken Knapp)
Operations: George Stephens
Contact Address: SSDFireTeam@noaa.gov