brightness temperature


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brightness temperature

In radio astronomy, a source of surface brightness (i.e., flux density per unit solid angle) B has a brightness temperature of T B = B λ2/(2k ), where λ is the observing wavelength and k is the Boltzmann constant. If the source of that radiation is a black body, and the observing wavelength sufficiently long, the brightness temperature will equal the temperature of the black body. In the case of an interstellar cloud, it may equal the physical temperature of the cloud if the radiation is by thermal emission and the cloud is optically thick (see optical depth). If the cloud is optically thin, the brightness temperature is reduced.

Sources that radiate by nonthermal emission can have very high brightness temperatures (>109 K). See also antenna temperature.

brightness temperature

[′brīt·nəs ‚tem·prə·chər]
(thermodynamics)
References in periodicals archive ?
The brightness temperature variations for each channel are caused primarily by the complicated ocean surface structure.
Time series of brightness temperature data from SSM/T-2, and corresponding simulations from ERA-lnterim and ERA-20C.
where T([xi], [eta]) is the brightness temperature, ([xi], [eta]) = (sin [theta] cos [phi], sin [theta] sin [phi]) the direction cosines with respect to (x,y) axes as shown in Figure 1, and ([u.
The brightness temperature due to this noise depends on the RF frequency and elevation angle.
Samples of GPM datasets at different levels, a) Level-1C GMI common calibrated brightness temperatures at 37 GHZ showing Tropical Cyclone Nanauk over the Arabian Sea on 11 Jun 2014.
Jackson, 1996: Interannual variability of upper-tropospheric water vapor band brightness temperature.
8 [micro]m) image, and the associated brightness temperature values are plotted from west to east along a 1500-km line centered on the eye of Typhoon Vongfong; brightness temperatures range from 190 K (cold, clouds near the eye) to 290 K (clear skies in the eye and farther away over warm ocean surfaces).
Microwave brightness temperature of the ocean is strongly dependent on variations in surface emissivity associated with increasing foam coverage due to whitecap and streaks induced by wave breaking, wind shear of the wave crest (Holthuijsen et al.
The new instrument will utilise a so-called hyperspectral measurement approach which in microwave terms means continuously sampled brightness temperature in absorption bands with high frequency resolution.
The principle of SAIR is to measure the spectral components of the brightness temperature distribution in the FOV by microwave interferometry.
Each complex correlation is a sample of the visibility function which, in the ideal case, is the spatial Fourier transform of the brightness temperature distribution [6].
and the brightness temperature in the extreme ultraviolet scarcely exceeds 4 000 degrees.