Click on the image above to download the associated loop images.
The 3.9 um image shown above corresponds to the VIS imagery on the previous page. These day-time images are displayed as reflectivity (see earlier discussion on emission and reflection in the "Basic Radiation Science" section), so that lighter shades are hot and darker shades are cool. Animation reveals small, bright pulses at several locations; each one showing controlled-burn fires. Notice that there are considerably more fires than were apparent in the VIS images. At 3.9 um, smoke plumes are difficult to detect because of poorer spatial resolution (when compared with VIS imagery) and poorer reflective properties. In this example, smoke can be observed as very subtle, dark areas emanating from the two larger fires.
Notice that the fire pixels seem to be "smeared" in the east-west direction. This is due to: 1) sensor lag, a part of the signal from hot spots is retained by the sensor, affecting the values of at least one other pixel down-scan from the hot spot; and 2) oversampling, the 3.9 um IR sensor observes an area of 4 x 4 km and is oversampled by a factor of 1.75 in the east-west direction.
Twelve controlled burns can be found in this animation sequence; the arrows are placed to help locate seven of them.