Satellite are mainly two types. 1. Natural Satellite and 2. Artificial satellite. Earth has a Natural Satellite name Moon. and Artificial satellite: which constructed by Humans which send it by using rocket in different different types of earth's orbits. Satellites have different shape and different purpose. in these satellite, solar panel are attached which convert the solar energy to electrical energy, due to this electrical energy, satellite are works properly and due to this battery are not need.
- Low Earth orbit (LEO) – from 200 to 2,000 km, for example, the ISS orbits at 400 km with a speed of 28,000 km/hour, and time for one orbit is about 90 minutes.
- Medium Earth orbit (MEO) – Most MEO satellites are at an altitude of 20,000 km, and time for one orbit is 12 hours.
- Geostationary orbit (GEO) – 36,000 km above the Earth. Time for one orbit is 24 hours. This is to match the rotation of the Earth so that the satellite appears to stay above the same point above the Earth’s surface. This is used for many communications and weather satellites.
The altitude chosen for a satellite depends on the job it is designed for.
Types of satellites:
Navigation satellites: 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.
Communication satellites: 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.
Weather satellites: 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.
Astronomical satellites: 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. Recently NASA launch a James Wed Space telescope.
International Space Station (ISS): International space station(ISI) are first human made space station which orbit the earth and distance form the earth's surface is about 400km, the ISS travels at a speed of 28,000 km/h and complete one rotation around the earth is about 90min.. This is a habitable space laboratory. Scientists inside the ISS are able to perform many valuable experiments in a microgravity environment.