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Question:

What is the minimal change in temperature that is detectable from the Landsat 7 thermal band imagery?

Answer:

Minimal detectable change in at-sensor radiance is 0.067 W/m2/srad/µm for the low gain setup (6L) and 0.037 W/m2/srad/µm for the high-gain setup (6H). This is equivalent to 0.5 K and 0.27 K at temperature of 300 K for low and high gain setup, respectively.

Due to nonlinear relationship between radiance and temperature, defined by the Planck’s law, the minimal detectable change of temperature is not constant over the entire range of measurable temperatures. It is, for example, 0.59 @ 280 K and 0.43 @ 320 K for low gain, and 0.33 @ 280 K and 0.24 @ 320 K for high gain.