Satellites For Kids - Artificial Satellites Information For Kids

How far can you throw a ball?

About 60 or 70 feet (18 or 21 meters)?

Why doesn't it travel any farther?

Gravity limits the distance.

When you throw a ball, it rises into the air, but the earth's gravity soon pulls it back to the ground.
To launch a spacecraft, we somehow have to overcome gravity.
How do we do this?
We do it by speed.
Think of yourself throwing the ball. If you throw the ball gently, it goes slowly, and it doesn't travel very far. But the harder you throw it, the faster it travels, and the farther it goes. You are starting to beat gravity by speed.

If you could throw the ball faster and faster, it would go farther and farther before it dropped back to the ground. Eventually, you could make it go so fast that its curve, as it fell, would be the same as the curve of the earth's surface. In other words, it would stay the same distance above the surface.
It would then be in orbit around the earth.

To launch your ball into orbit you would have to give it a speed of more than 12 times that of a rifle bullet!

The speed is over 17,000 miles (27,400 kilometers) an hour.

This is known as the orbital velocity.

If you wanted to send your ball to Mars or another planet, you would have to throw it even faster, at a speed of just over 24,800 miles (40,000 kilometers) an hour. Then it would escape earth's gravity completely.

This speed is called the escape velocity.

Equatorial orbits go around the equator. Polar orbits go over the poles. In a geostationary orbit, a satellite keeps pace with the earth's rotation and appears fixed in the sky.
Space scientists send their satellites into orbit at orbital velocity. Up in space, about 186 miles (300 kilometers) above the earth, a satellite circles around the earth in about one hour.

How does satellite stay circling up in space?
Why doesn't it soon slow down and fall back to earth?

The reason is that there is neither air nor anything else to cause friction, which would slow it down. So it circles round and round at the same speed.

When was the first satellite launched into space?

In 1957, the first artificial satellite was successfully launched into orbit around the earth.
Since then, more and more satellites have been launched into orbit.
These satellites are helpful to people in many different ways.
Communications satellites carry telephone calls and television programs between the earth's continents.
Weather satellites help people to make accurate weather forecasts.
Earth-survey satellites help people to make better maps and find where useful minerals are.
Astronomers use satellites to study the universe.

What are satellites made of?

Satellites are built of lightweight materials. They are not streamlined, nor smooth like airplanes.
Can you think why?
No matter what they are used for, most satellites have certain things in common. They carry a radio and several antennas.
Some of the antennas are shaped like dishes.
Satellites carry various measuring instruments and sometimes cameras.
The radio sends, or transmits, the information back to Earth.
On many satellites, there are large, flat parts that look like paddles. These are solar cell panels which capture the energy in sunlight and change it into electricity. The electricity powers the instruments and radio on board the satellite. Sometimes, the solar cells are fixed around the outside of the satellite.

Communications and tracking

Scientists use radio to send signals to satellites and receive information from them. Satellites whizz endlessly around the earth. But you cannot send signals to a satellite if it is on the opposite side of the earth, because the earth blocks the signals.

Tracking Satellites

Before scientists can communicate with a satellite, they must know where it is.
They must have a means of following, or tracking, it all the time.
Again, they do this by radio.
They use large dish antennas at tracking stations to listen for the satellite's signals. The antennas track the satellite's movement across the sky and exchange signals with it.
It is even more important for astronauts to keep in contact with the earth, so that the scientists on earth can check that everything is working properly.
The main communications center for manned trips in space is called Mission Control.
The most famous Mission Control center is in Houston, Texas.