Noise (2 of 2)

Fig. 4e is a plot of noise equivalent temperature as a function of scene temperature for the 3.9 and 10.7 um channels. The figure shows that the accuracy with which temperature can be measured at 3.9 um is worse than 2 K for scene temperatures below about 250 K. On the other hand, at 10.7 um, the accuracy is always better than 0.5 K for all possible scene temperatures.

Another way of showing the effect of low scene radiance at 3.9 um is by inspecting the signal-to-noise ratio (S/N) versus temperature, Fig. 4f. Signal-to-noise, as used here, is the ratio of the scene radiance divided by GOES' radiance accuracy. Fig. 4f shows that the 10.7 um channel has a much better S/N than the 3.9 um channel. In fact, the S/N at 3.9 um decreases to where there is no signal above noise at temperatures below about 230 K, making this channel of little use at colder scene temperatures.

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