Fire Detection (1 of 5)
Its strong sensitivity to sub-pixel "hot-areas" makes the 3.9 um channel very
useful in fire detection. Fig. 5a may be used to compare the temperatures
at 3.9 and 10.7 um with the percent of a pixel covered by fire, where the
hot-area is at 500 K and the remainder of the pixel is at 300 K. Note that if
only 5% of the pixel is at 500 K, the 3.9 um measured brightness temperature
of that pixel is 360 K, while the corresponding 10.7 um brightness temperature
is less than 320 K.
Fig. 5b shows the DIFFERENCE in the brightness
temperature for the 3.9 and 10.7 um pixel, hypothesized in this example. Note
how much more responsive the 3.9 um channel is over smaller fire areas.
NOTE: Refer to the text with Fig. 2c, in the "Energy Sources" section, for an
important caveat regarding 3.9 um channel saturation.
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