Noise temperature is a measure of noise in electronic devices (or virtually anything that carries electricity), expressed as a temperature, as if the noise is thermal noise resulting from a device's temperature. Thermal noise is a primary cause of noise in electronics, and in that case, expressing it as the temperature is an obvious concept, but other sources of noise can be expressed as a temperature, allowing a means of comparison of noise contributors. Antenna temperature is an expression of antenna noise in such manner. The term radiometric noise is sometimes used for all the noise generated by the use of some particular radio telescope including thermal noise, antenna noise, etc.
Noise temperature is defined as:
Tnoise = Pnoise / ( B kB )