Q 2.4 Which orbits are used for satellite communications?
A majority of communication satellites are located in a geostationary orbit wherein satellites appear stationary from the Earth. At an orbital altitude of about 35786 km and an inclination of 0o a satellite’s orbital motion coincides with that of the Earth’s axial rotation. Thus a satellite in this orbit appears stationary from the Earth. Geostationary satellites can cover up to 1/3rd of the globe and hence provide instantaneous connectivity between locations separated by thousands of kilometre noting that the equatorial distance of 1/3rd globe is approximately 13358.4 km. We assume a circular equator with an average radius of 6378.14 km for this calculation.
Several systems use low Earth orbit (LEO) or medium Earth orbit (MEO) ranging in altitude between about 700 km and 24000 km. LEO and MEO satellite systems require handovers between satellite or Earth stations because satellites rise and set regularly. As such the system architecture and constellation management is more complex than geostationary satellite systems.