Sentence:  Recent interferometer measurements ( Radhakrishnan and Roberts , 1960 ) have shown the 960 - Mc emission of Jupiter to be partially polarized and to originate in a region of larger <WSD>diameter</WSD> than the visible disk . 
Meaning of the word marked with <WSD> tags:  the length of a straight line passing through the center of a circle and connecting two points on the circumference