Ways are described to minimize errors when the Planck law is used for single- and two-color temperature measurements. Various approximations useful in remote sensing are discussed, as well as a suggested method for measuring temperature and emissivity simultaneously with active and passive systems at each of two wave-lengths. Measurements at multiple wavelengths are also presented in this mathematical discussion.
Charles E. Campbell,
"Use Of The Planck Law In Remote Sensing", Proc. SPIE 0027, Remote Sensing of Earth Resources and the Environment, (1 May 1972); doi: 10.1117/12.978128; https://doi.org/10.1117/12.978128