# Geostationary Orbits(OCR A Level Physics)

Author

Katie M

Expertise

Physics

## 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

#### Exam 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

You will also be expected to remember that the time period of the orbit is 24 hours for calculations on a geostationary satellite.

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