radio_radiation has definitions from the field of physics
[ noun ] (physics) an electromagnetic wave with a wavelength between 0.5 cm to 30,000 m

Used in print

(Cornell H. Mayer, "Radio Emission of the Moon...)

The observable characteristics of planetary radio_radiation are the intensity , the polarization , and the direction of arrival of the waves .

The radio_radiation of the sun which is reflected from the moon and planets should be negligible compared with their thermal_emission at centimeter wave_lengths , except possibly at times of exceptional outbursts of solar radio_noise .