Sentence:  Statistically , the most significant data have been collected from the <WSD>sensors</WSD> on 1958 Alpha ( Explorer 1 , ) , 1958 Delta 2 ( Sputnik 3 , ) , and 1959 Eta ( Vanguard 3 , ) . 
Meaning of the word marked with <WSD> tags:  any device that receives a signal or stimulus (as heat or pressure or light or motion etc.) and responds to it in a distinctive manner