Question

How many Geo- Centric satellites on channels for teleconferencing are needed for distant countries?

• A. Two
• B. Three
• C. Four
• D. Five

Hint:

Arthur C. Clarke first proposed in 1945 that exactly three geostationary satellites placed at equal distances could provide complete, worldwide radio and television coverage.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
A geostationary (geocentric) satellite orbit is located directly above the Earth's equator at an altitude of approximately 35,786 km. At this altitude, the satellite's orbital period matches the Earth's rotation, making it appear stationary over a fixed point on the ground.

Step 2: Detailed Explanation:
Because of the spherical curvature of the Earth, a single geostationary satellite can only cover or view approximately one-third ($120^\circ$ of longitude) of the Earth's surface.
To establish a continuous, global telecommunications and teleconferencing link across distant countries worldwide (excluding the extreme polar regions), we need a minimum of:
\[ \text{Minimum Satellites} = \frac{360^\circ \text{ (Total Earth Sphere)}}{120^\circ \text{ (Single Satellite Coverage)}} = 3 \]
Therefore, three strategically positioned geostationary satellites separated by $120^\circ$ intervals are required to provide complete global coverage.

Step 3: Final Answer:
Three geocentric satellites are needed, corresponding to Option (B).