I used to work for NRAO. Arecibo is a transmitter, which illuminates the asteroid with very high powered radio waves. The asteroid reflects some of the radio wa

I used to work for NRAO. Arecibo is a transmitter, which illuminates the asteroid with very high powered radio waves. The asteroid reflects some of the radio waves, which is received back on the ground at Arecibo or at other radio telescopes like Greenbank or the Very Large Array.