An illustration of a space shuttle, with its payload doors open, sending and receiving radar signals

Imaging radar works by bouncing a radio signal off the ground. Image Credit: NASA

      a device that sends out radio waves and picks them up again after the waves strike another object and bounce back

Radar is used to help predict weather and measure waves of the ocean.

Police officers can tell how fast a car is going by using a radar device.

More Information:
http://spaceplace.nasa.gov/en/kids/srtm_makemap3.shtml   →
http://southport.jpl.nasa.gov/desc/imagingradarv3.html   →
http://southport.jpl.nasa.gov/html/sat_animation.html   →
http://science.nasa.gov/headlines/y2008/29feb_radarmoon.htm   →