ISO/TC 211 Multi-Lingual Glossary of Terms (MLGT)

Note 1 to entry: In the Rayleigh-Jeans limit, the microwave power per unit bandwidth received by a radiometer, ${\displaystyle P}$ , is:

Note 2 to entry: ${\displaystyle P=\text{k}\cdot T_B}$

Note 3 to entry: where ${\displaystyle \text{k}}$ is the Boltzmann's constant (${\displaystyle \text{k}=1.38064852\times {10}^{-23}\text{J/K}}$ ).

Note 4 to entry: For the frequency range of microwave, Planck's radiation law can be well approximated by the Rayleigh-Jeans formula. Usually the microwave radiometers use the Rayleigh–Jeans equivalent brightness temperature, which is defined as: ${\displaystyle T_{\text{b,v}}^{\text{(RJE)}}=\frac{c^2}{2v^2\text{k}}{I}_{\text{v}}}$ where ${\displaystyle T_{\text{b,v}}^{\text{(RJE)}}}$ is the Rayleigh–Jeans equivalent brightness temperature; ${\displaystyle v}$ is the frequency in Hz; ${\displaystyle \text{c}}$ is the velocity of light (${\displaystyle 2.997925\times {10}^8\text{m}/\text{s}}$ ); ${\displaystyle \text{k}}$ is the Boltzmann’s constant (${\displaystyle 1.38064852\times {10}^{-23}\text{J}/\text{K}}$ ); ${\displaystyle I_{\text{v}}}$ is the radiance.