Astronomy and space science - Satellites

Artificial satellites

Artificial satellites are built by people and launched by rockets into space, where they orbit around the Earth. 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

Space telescopes

Hubble Space Telescope - image courtesy of NASA

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. Some space probes go into orbit around other planets, some land on them, and some even journey out of the solar system.

Space exploration

People have flown to the Moon and landed on it. But so far that is the furthest people have travelled from Earth. It takes years to travel to other planets, like Mars, and people have not done this yet.

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