Artificial satellites are built by people and launched into orbit around the Earth. They are very useful to us. These are some of the things that artificial satellites are used for:
Communications, including broadcasting television programmes and relaying telephone calls
Global Positioning System (GPS) and Galileo satellites for navigation
Collecting information to help with weather forecasts
Scientific surveys of the Earth's surface
Map making
Spying
Some satellites are used to collect information about the planets and stars. The Hubble Space Telescope can see further into space than telescopes based on the ground. Its view is not blocked by clouds and it doesn't have to wait for night-time. However, it is difficult and expensive to launch and maintain. If anything goes wrong, only astronauts can fix it.
Space probes
Space probes do not orbit the Earth. Instead, they travel to other planets to collect scientific information. People have been to the Moon in the last century, but it would take too long to send people to other planets. Some space probes go into orbit around other planets, some land on them, and some even journey out of the solar system.
