Satellites can be launched into 2 kinds of orbits, POLAR and EQUATORIAL. See animation below.
POLAR ORBIT: These type usually have fast speeds, lower orbits. They travel from north to south around one side of the Earth and then back north round the other side. They pass over different parts of the Earth as the Earth turns on its axis. The result is that the satellite appears to travel a spiral path over the Earth's surface.
EQUATORIAL ORBIT: In this case the satellites travel eastwards in an orbit directly above the equator. These type of satellites usually have moderate speeds and high orbits, altitude of around 36,000 Km. At this height they take one day to make one complete orbit. However, the Earth is spinning beneath the satellites in the same direction and as a result each satellite appears to remain in one place above a point on the equator.
The entire Earth can be covered by just 3 geo-stationary satellites. See animation on below.
If you 'ring' Australia, a microwave radio signal is transmitted from a 'dish' aerial up to the satellite. In turn the satellite transmits it down to another dish aerial in Australia (see animation below). Microwave are used since they travel in a narrow bands, in straight line, and pass easily through the Earth's atmosphere. See animation below.
Similarly, television satellites canbroadcast programmes towhole continents, for example all of Europe. To view programmes, you need a satellite dish aerial on your premises to pick up the signal. See animation below.
There are 4 main types.
Monitoring the Weather - they take photographs of the weather, and send the picture back to Earth by radio signals. These aregeo-stationary ofsynchronous.
Observing and Exploring the Earth - very useful for land survey. These are lower satellites that take photographs in very fine detail. These are very important in spotting forest fires, pollution, crude oil deposits and the health of crops.
Communication and Navigation - Military use these for spying. These are also used to guide ships and planes on their journey.
Exploring the Solar System and Universe - These type of satellites are equipped with telescopes. They can take very detailed pictures of planets, because they are away from the Earth's atmosphere.