| Satellite Technology | | | | Satellite technology and instruments |
| Satellite technology has become part of all our | | | | Every satellite launched into space will carry its own |
| everyday lives. From telling us what the weather is | | | | unique set of instruments or technology, relevant to |
| going to be like, and how to get from one place to | | | | the mission. So a satellite studying outer space will |
| another, to offering us a far wider choice of | | | | have a telescope that can see in different |
| programmes to watch on TV. | | | | wavelengths of light, one monitoring the weather |
| | | | might have a camera to measure cloud movement, |
| Satellite is a word that simply refers to one body | | | | while one used for communications will carry a |
| orbiting another. There are natural satellites that orbit | | | | payload that allows it to redirect messages back to |
| planets, such as our Moon, and artificial, man-made | | | | one part of the Earth that have been sent up from |
| satellites that serve a variety of different purposes. | | | | another part. |
| The first man-made satellite, Sputnik 1, was sent into | | | | They will also have a group of devices called |
| space on 4 October 1957 by the former Soviet | | | | "subsystems" that will help power the satellite, |
| Union. Today there are over 3,000 satellites in orbit, | | | | co-ordinate the instruments and send data back to |
| owned by more than 40 countries worldwide. | | | | Earth. The subsystem that powers the satellite will |
| What are they used for? | | | | usually include solar panels that gather energy from |
| Man-made satellites have six main uses: | | | | the Sun. |
| - Scientific investigation | | | | How are satellites launched? |
| - Earth observation | | | | Some satellites, such as Hubble, are launched via a |
| - Weather | | | | space shuttle. But the majority will be sent into orbit |
| - Communications | | | | on rockets, which then fall into the ocean when |
| - Navigation | | | | they've used up all their fuel. |
| - Military | | | | How do they remain in orbit? |
| What are the different types of orbit? | | | | Two factors combine to keep a satellite in orbit: |
| There are many different orbits a satellite can be put | | | | - the speed of the satellite |
| into, depending on what it's being used for. But the | | | | - the gravitational pull between the Earth and the |
| majority use one of the following orbits. | | | | satellite |
| - Geosynchronous Earth Orbit (GEO) is where the | | | | This is similar to attaching a ball to a string and |
| satellite sits directly over the equator, about 35,775 | | | | swinging it around in a circle. If the string were to |
| km above Earth. It will rotate in the same direction | | | | break, the ball would fly off in a straight line. But |
| and at the same speed as our planet, so always | | | | because it is tethered (like gravity tethers a satellite), |
| appears to be in the same place in the sky. | | | | it orbits you instead. |
| Communications and some weather satellites are | | | | What happens they stop working? |
| placed in this type of orbit. | | | | A satellite will stay in orbit until it starts slowing down. |
| - Low Earth Orbit (LEO) is commonly described as | | | | Gravity will then pull it into a denser part of the |
| the region between 200 and 2,000 km. Most | | | | atmosphere, the friction generated as the satellite |
| artificial Earth satellites are placed in LEO, where they | | | | moves at very high speed through this denser |
| travel at about 27,000 km/h (8 km/s), making one | | | | atmosphere generates a lot of heat which can be |
| revolution in about 90 minutes. Different orbits are | | | | enough to cause the satellite to burn up before it |
| used for different applications, e.g. Earth observation | | | | reaches the Earth's surface. The ones that are too |
| satellites often use the Sun synchrous orbit, travelling | | | | big to burn up are guided to come down in a remote |
| over the Poles and thus seeing most of the Earth's | | | | part of the ocean away from people. |
| surface over time, while LEO communications | | | | What is small satellite technology? |
| satellites travel in orbits centred on the equator. | | | | Small satellite technology, being pioneered in the UK, |
| Some scientific missions such as Hubble look out into | | | | uses a range of new techniques that enable scientists |
| space from LEO. | | | | to build and launch satellites faster and for much less |
| - Medium Earth Orbit (MEO) has many definitions but | | | | money than previously possible. |
| is essentially the region above LEO (2,000 km) to | | | | Many of these new small or "micro" satellites are |
| 1,000 km below GEO (34,775 km). This region is | | | | currently being tested to determine whether simple, |
| used by the various Global Navigation Satellite | | | | economically-built spacecraft can achieve the same |
| Systems (GNSS). The European Galileo system will | | | | results as traditional satellites. |
| reside there as well as the existing US GPS and the | | | | If successful, these new techniques could have a |
| Russian Glonass. Many other satellites pass through | | | | huge impact on the future of space missions and |
| this region either operationally or during deployment. | | | | significantly reduce the cost of launching satellites. |