What is a satellite?
A satellite is any object that orbits a planet or star. The Moon is Earth's natural satellite, while artificial satellites are machines launched into orbit for communication, navigation, weather and science.
Artificial satellites stay in orbit by moving fast enough sideways that they keep falling around Earth instead of falling to the ground. The first artificial satellite was Sputnik 1, launched by the Soviet Union on October 4, 1957. It was a metal sphere about the size of a beach ball that sent out radio beeps.
Satellites orbit at different heights. Low Earth orbit, a few hundred kilometers up, is used by the International Space Station and internet constellations. Navigation satellites, such as GPS, orbit about 20,000 kilometers up. Geostationary satellites, about 35,786 kilometers above the equator, match Earth's rotation and seem to hover over one spot.
What satellites do
Satellites provide TV broadcasts, phone calls, internet access and GPS navigation. They track weather, monitor forests, ice and oceans, help with disaster response and study space. Many everyday services, such as bank transactions, rely on precise time signals from satellites.
Did You Know?
Many moons in the solar system are natural satellites. Saturn has more than any other planet, with 274 confirmed moons.