The GPS (global positioning system) is made up of 24 satellites that orbit at an altitude of 20,000 km above the surface of the Earth. The difference in time for signals received from four satellites is used to calculate the exact location of a GPS receiver on Earth.
These are used for television, phone or internet transmissions, for example, the Optus D1 satellite is in a geostationary orbit above the equator and has a coverage footprint to provide signals to all of Australia and New Zealand.
These are used to image clouds and measure temperature and rainfall. Both geostationary and low Earth orbits are used depending on the type of weather satellite. Weather satellites are used to help with more accurate weather forecasting.
Earth observation satellites
These are used to photograph and image the Earth. Low Earth orbits are mainly used so that a more detailed image can be produced.
These are used to monitor and image space. A satellite such as the Hubble Space Telescope orbits at an altitude of 600 km and provides very sharp images of stars and distant galaxies. Other space telescopes include Spitzer and Chandra.
Kinetic bombardment satellites
this type of satellite drops steel rods which will be more powerful than the most powerful a-bomb.
International Space Station (ISS)
This is a habitable space laboratory. At an altitude of 400 km, the ISS travels at a speed of 28,000 km/h and orbits the Earth once every 92 minutes. Scientists inside the ISS are able to perform many valuable experiments in a microgravity environment.