Antenna noise temperature

In telecommunication, antenna noise temperature is the temperature of a hypothetical resistor at the input of an ideal noise-free receiver that would generate the same output noise power per unit bandwidth as that at the antenna output at a specified frequency.

Note 1: The antenna noise temperature depends on antenna coupling to all noise sources in its environment as well as on noise generated within the antenna.

Note 2: The antenna noise temperature is a measure of noise whose value is equal to the actual temperature of a passive device[?].

Source: from Federal Standard 1037C and from MIL-STD-188