For global communication coverage, what is the minimum number of satellites required in geostationary orbit?
Electronics and Communication Engineering
Satellite Communication
Difficulty: Easy
Choose an option
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A1
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B3
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C10
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D5
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E6
Answer
Correct Answer: 3
Explanation
Introduction / Context:Geostationary satellites are positioned approximately 36,000 km above the equator. From this altitude, they can cover about one-third of Earth's surface. This principle is used in global satellite communication systems.
Given Data / Assumptions:
- Earth circumference ≈ 40,000 km.
- Coverage of each geostationary satellite ≈ one-third of Earth's surface.
- Satellites must be spaced evenly to provide continuous coverage.
Concept / Approach:Since each satellite covers about 120° longitude, three satellites equally spaced at 120° intervals can provide nearly full global communication coverage, except for polar regions.
Step-by-Step Solution:
Total angular coverage required = 360°.Coverage per satellite ≈ 120°.Number of satellites required = 360° / 120° = 3.Verification / Alternative check:
Systems like INTELSAT confirm this with 3-satellite networks providing global coverage.Why Other Options Are Wrong:
1: insufficient, covers only one-third of the globe.5 or 10: more than required, although they improve redundancy.6: similar reasoning, unnecessary for minimum coverage.Common Pitfalls:
Assuming polar coverage—geostationary satellites cannot cover extreme polar regions.Final Answer:
3