Geostationary Orbits & Satellites
- Many communication satellites around Earth follow a geostationary orbit
- This is sometimes referred to as a geosynchronous orbit
- This is a specific type of orbit in which the satellite:
- Remains directly above the equator
- Is in the plane of the equator
- Always orbits at the same point above the Earth’s surface
- Moves from west to east (same direction as the Earth spins)
- Has an orbital time period equal to Earth’s rotational period of 24 hours
- Geostationary satellites are used for telecommunication transmissions (e.g. radio) and television broadcast
- A base station on Earth sends the TV signal up to the satellite where it is amplified and broadcast back to the ground to the desired locations
- The satellite receiver dishes on the surface must point towards the same point in the sky
- Since the geostationary orbits of the satellites are fixed, the receiver dishes can be fixed too
Geostationary satellite in orbit
Worked example
Calculate the distance above the Earth's surface that a geostationary satellite will orbit.
Mass of the Earth = 6.0 × 1024 kg
Radius of the Earth = 6400 km
Examiner Tip
Make sure to memorise the key features of a geostationary orbit, since this is a common exam question. Remember:
- Equatorial orbit
- Moves west to east
- Period of 24 hours
