A satellite is a planet, moon or machine that orbits a planet or star.
Planets and moons are called natural satellites and machines referred to as artificial satellites.
Our own Earth is a natural satellite as it orbits the sun and our Moon is a natural satellite as it orbits Earth.
Most of the major planets (except Mercury and Venus) have moons. Pluto and other dwarf planets, as well as many asteroids, also have small moons.
Most of the satellites we talk about are man-made. There are over 6,000 satellites orbiting the Earth at the moment.
Our planet – Some take pictures of the Earth to help meteorologists predict our weather and track things like hurricanes, wildfires, how ice is melting and how seas are rising. Other satellites can help scientists predict the spread of disease or even help farmers decide which crops to plant.
Our universe – Satellites also monitor other planets, the sun, black holes, other galaxies and dark matter, to give us a better understanding of the solar system and universe.
Our lives – Other satellites are used mainly for communication, such as beaming phone or TV signals around the world. We’ve all heard of GPS (Global Positioning System), which enables us to pinpoint exact locations. This is possible because of over 30 navigation satellites orbiting the world. Signals from these satellites are received by our phones. Once we receive a few signals from these satellites, our phones can work out our precise location.
Our extremely accurate weather forecasts are partly a result of weather satellites. As well as land-based weather monitoring, such as measuring atmospheric pressure, temperature, wind speed, wind direction, humidity, and precipitation, weather satellites provide us with vital information about weather forecasts.
Weather satellites carry instruments called radiometers that scan the Earth to form images. These instruments usually have a small telescope, a scanning mechanism, and detectors that detect either visible, infrared, or microwave radiation for the purpose of monitoring weather systems around the world.
Most satellites are launched into space on rockets. They then orbit Earth by balancing their speed with the pull of Earth’s gravity. Satellites orbit Earth at different speeds and heights.
One of the most recent launches (this month), was by Sir Richard Branson’s Virgin Orbit Company. It succeeded in putting its first 10 satellites in space, using a rocket, which was launched from an old 747 jumbo jet. These 10 ‘CubeSat’ devices are miniature satellites made up of multiple cubic modules of 10cm x 10cm x 10cm. Having initially been developed as educational tools, CubeSats are increasingly being used in orbit for technology demonstration, scientific studies, and even commercial purposes. And just like other satellites, they are custom built for specific missions.
Whatever shape, size and purpose of a satellite, most have at least two elements in common – a power source and an antenna. The antenna sends and receives pieces of information (often to and from Earth) and the power source is either a battery or a solar panel. Other items that satellites carry include cameras and sensors.
Here are some of the most famous satellites from the past 63 years.