Sentence:  Not all the observers have used the same procedures or made the same assumptions about the lunar brightness distribution when reducing the data , and this , together with differences in the <WSD>methods</WSD> of calibrating the antennae and receivers , must account for much of the disagreement in the measured radio brightness temperatures . 
Meaning of the word marked with <WSD> tags:  a way of doing something, especially a systematic way; implies an orderly logical arrangement (usually in steps)