Sentence:  In the observations at 4.3 mm ( Coates , 1959 a ) , the diameter of the antenna beam , 6 ' .7 , was small enough to allow resolution of some of the larger features of the lunar surface , and contour <WSD>diagrams</WSD> have been made of the lunar brightness distribution at three lunar phases . 
Meaning of the word marked with <WSD> tags:  a drawing intended to explain how something works; a drawing showing the relation between the parts