Space physics QWC practice question
Question
A communication satellite is placed in a geostationary orbit. Explain the conditions needed for this orbit and why it is useful for communication. [6 marks]
Student guidance
State the orbital conditions before explaining the communication advantage.
Expected physics points
- The satellite orbits above the equator in the same direction as Earth's rotation.
- Its orbital period is 24 hours, matching Earth's rotation period.
- The orbit is circular and the satellite remains at a fixed height/ distance.
- Its angular speed matches the angular speed of the point on Earth below it.
- It appears stationary above one point on Earth.
- A fixed ground antenna can therefore point at it continuously for communication.
Mark scheme points
- The satellite orbits above the equator in Earth’s rotation direction.
- Its period is 24 hours, matching Earth’s rotation period.
- The orbit is circular at a fixed height or distance.
- Its angular speed matches the point on Earth below it.
- It appears stationary above one point on Earth.
- A fixed antenna can point at it continuously for communication.
Indicative content
- The satellite orbits above the equator in the same direction as Earth's rotation.
- Its orbital period is 24 hours, matching Earth's rotation period.
- The orbit is circular and the satellite remains at a fixed height/ distance.
- Its angular speed matches the angular speed of the point on Earth below it.
- It appears stationary above one point on Earth.
- A fixed ground antenna can therefore point at it continuously for communication.
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