# Explain why artificial satellites in low Earth orbit must be given an occasional boost from their engines to maintain their orbital altitude.

> Eduqas GCSE Physics — 10.1 Solar system; stability of orbital motions; satellites · Explain · 4 marks

> Low Earth orbit satellites travel at altitudes between approximately 200 km and 2000 km above Earth's surface. At these altitudes, a very thin atmosphere still exists.

## Mark scheme (4 marks)

1. The thin atmosphere exerts a drag force / air resistance on the satellite
2. The drag force causes the satellite to lose (kinetic) energy / slow down
3. As the satellite slows, gravitational force is no longer balanced / gravity pulls the satellite to a lower altitude
4. Engine boost increases the satellite's speed / restores the correct orbital speed to maintain the original altitude

## Key terms

- [low Earth orbit](https://www.gradenine.co.uk/glossary/low-earth-orbit)
- [orbital altitude](https://www.gradenine.co.uk/glossary/orbital-altitude)

## Related

- [Revision notes for Eduqas GCSE Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-artificial-satellites-in-low-b876c3eb) · Published by Druglandscape Ltd.