Sentence:  No attempts to measure the <WSD>radio</WSD> emission of the remaining planets have been reported , and , because of their distances , small diameters , or low temperatures , the thermal radiation at radio wave lengths reaching the earth from these sources is expected to be of very low intensity . 
Meaning of the word marked with <WSD> tags:  an electromagnetic wave with a wavelength between 0.5 cm to 30,000 m