satellites are spacecraft that beam radio signals around the world. Satellites are located
all around the earth. Some fly as low as 200 miles above the earths surface. Some
satellites are as high as 22,300 miles above the earth. The higher the satellite is, the
more area on the earth it can cover.
Have you used a
satellite today? You probably did and didnt even know it! Signals come from
telephone calls, television programs and information sent and received from computers.
All kinds of information can be changed into radio signals
and sent anywhere on earth at the speed of light (thats fast!) in just a fraction of
a second. One satellite can handle thousands of telephone calls! The satellite must have
electricity to work, so they have large panels that gather power from the sun and convert
it into electricity.
Radio signals are sent from earth from huge dish-shaped
antennas up to a satellite orbiting around the earth. When the signal gets there,
its very weak because its traveled a LONG way. The satellite has special
equipment on board to make the signal stronger. After the signal is strengthened, the
satellite sends the signal back down to the earth, where it is received by another large
Think of what happens when you turn on a flashlight. When
you point the beam of light at a flat surface, the light gets more focused if you get
closer and gets wider as you get further away. This is kind of like a satellite beam. The
signals sent back to earth from the satellite are like lightbeams from the flashlight.
When the radio beams come back to earth, another
dish-shaped antenna receives and strengthens the returning signal by collecting the signal
over the large dish area, and then bringing the radio beams together in one small spot
where the receiver is located.
The strengthened signal is then carried from the antenna
by cable to a ground station, where it is sent out over land systems like the telephone
company to be received by you!
Text by Debbie Linton. Ms. Linton works for Information
Technology and Applications Corporations Fort Gordon, Ga., branch, as contract
support to the military satellite communications project manager and Training and Doctrine
Commands satellite communications systems manager. Shes a retired Signal Corps
major who began her career as an Army air-traffic controller and completed it as an Army
satellite communications architect. She has continued her satellite architectural work as
a civilian and is author of the Armys satellite communications architecture book.
Click above to see how a satellite beams signals to the
Click above to see how signals are bounced from satellite to
Click above to see how satellites are used in a telephone