Satellites can be grouped into 5 different classes based on the specific applications for which they are designed. The different groups of satellites have contrasting orbit heights. Though the five different groups of satellites are briefly described here, most of the discussions in this design guide are focused on Earth observing satellites.
- Communication satellites help to provide radio, television and phone coverage. These satellites are positioned at fixed points above the equator as they revolve around the Earth once each day (geostationary).
- Weather satellites can be geostationary to observe evolving conditions in one hemisphere, or polar orbiting to collect global information each day that is used for weather forecasting.
- Navigational satellites are special satellites in high orbits that help us to find our exact location on the Earth. GPS (Global Positioning Systems) receivers that you can now buy at many stores use these satellites to show us our location.
- Satellites for planetary/astronomical studies point away from the Earth and are used to study outer space and other planets.
- Earth observing satellites often have orbits that are lower (about 700 to 800 km high) than the orbits of geostationary satellites (about 35,000 km high). Their orbits pass very close to the north and south poles (near polar). They are instrumental in providing data that promote the understanding of the complex Earth systems.
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