Sentence:  The direct evidence on the micrometeorite environment near the Earth is obtained from piezoelectric <WSD>sensors</WSD> ( essentially microphones ) and from wire gages ; these instruments are installed on rockets , satellites , and space probes . 
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