Radio telescopes, used in tracking and collecting data from satellites and space probes, are a form of directional radio antenna used in radio astronomy. They operate on the radio frequency portion of the electromagnetic spectrum where they detect radio sources. Radio telescopes are large parabolic antennas used singly or in an array and are located far from major centers of population in order to avoid electromagnetic interference.
Karl Guthe Jansky built the first radio antenna used to identify an astronomical radio source, in 1931. While on the assignment of identifying sources of static Jansky created his antenna that received short wave radio signals. He mounted the antenna on a turntable in order to rotate it in the direction of the static. Jansky identified three types of static: nearby thunderstorms, distant thunderstorms, and an unknown hiss. Eventually Jansky determined that the hiss came from out in the Milky Way Galaxy.
Grote Reber built the first parabolic radio telescope in his back yard in 1937. He later conducted the first sky survey at very high radio frequencies. After World War II the field of radio astronomy began to blossom. Since the electromagnetic spectrum that makes up the radio spectrum is very large the types of antennas vary widely in size and configuration. Typical antenna size is 82.25 feet and dozens of these operate all over the world.