The brightness temperature of a body is defined according to
where is the specific intensity and is given by the Planck Law. In radio astronomy, the Rayleigh-Jeans law can be used to approximate the Planck Law, so
where has MKS units of
Antenna Temperature, Brightness, Planck Intensity Density, Planck Law, Specific Intensity
References
Janssen, M. A. "An Introduction to teh Passive Microwave Remote Sensing of Atmospheres." Ch. 1 in Atmospheric Remote Sensing by Microwave Radiometry (Ed. M. A. Janssen). New York: Wiley, pp. 1-35, 1993.
Rybicki, G. and Lightman, A. P. Radiative Processes in Astrophysics. New York: Wiley-Interscience, pp. 25-26, 1979.
Thompson, A. R.; Moran, J. M.; and Swenson, G. W. Jr. Interferometry and Synthesis in Radio Astronomy. New York: Wiley, p. 8, 1986.
