What is the minimum number of artificial satellites required for communication throughout the globe?

This interesting question submitted to GKToday by Raju Das has also appeared in the West Bengal Civil Services Executive Examination- 2010.

It was first of all conceptualized by world famous science fiction writer Arthur C. Clarke who lived at his permanent residence in Colombo and died in 2008. Any of you, who read about this excellent author, would have easily ticked the correct option – 3 satellites.

Arthur C. Clarke described the concept of geostationary satellites in his work : “Extra Terrestrial Relays -Can Rocket stations give worldwide coverage? ” This work was published in 1945.

The link to his original work has been provided in the end of this answer.
Here is what he said” A single station could only provide coverage to half of the globe and for a world service 3 would be required, though more could be easily utilized.

The arrangement which was suggested by Clarke is shown in the following figure:

The stations would be arranged approximately equidistantly around the earth and the following longitudes appear suitable:
30°E – Africa & Europe
150°E – China & Oceania
90° W- The Americas
The station chain would be linked by radio or optical beams and thus any broadcast service could be provided.

The geostationary orbit is now sometimes referred as the Clarke Orbit or the Clarke Belt in his honor. Here is the work (file size 3 MB)

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