The Wildland Fire Assessment System derives information from the Advanced Very High Resolution Radiometer (AVHRR). The AVHRR is a radiation-detection imager, an instrument based on satellites used to provide images that can be used for remotely determining cloud cover and the surface temperature. Normalized Difference Vegetation Index (NDVI) data is used to help assess vegetation conditions across the United States. The NDVI Greenness maps help detect fire risk.