The U.S. Geological Survey (USGS) has advanced the use of moderate-resolution satellite data in a decision support system for assessing national fire potential. Weekly updated digital images of the Normalized Difference Vegetation Index (NDVI), based on data acquired at 1-kilometer (km) resolution (about 0.6 mi), have been used for the past 19 years as a means to assess live vegetation conditions for the purpose of rating fire danger. These images, produced and monitored through the growing season, portray the approximate time of greenup and senescence, as well as the relative amount and condition of growing plants.