To achieve continuous radio communication coverage all around the Earth, a minimum of three artificial satellites are required due to the nature of satellite orbits and the need for triangulation.
When it comes to satellite communication, satellites are typically placed in geostationary orbits around 35,786 kilometers (22,236 miles) above the Earth's equator. These satellites remain fixed relative to a specific point on the Earth's surface because they orbit at the same rate as the Earth's rotation. This allows them to provide continuous coverage to a specific region.
However, geostationary satellites have limitations when it comes to global coverage. Since they are positioned above the equator, their coverage becomes less effective the further away from the equator you go. At high latitudes, the signal from a geostationary satellite appears low on the horizon, resulting in weak and unreliable communication.
To overcome this limitation and achieve global coverage, a network of multiple satellites is used. By placing satellites in different orbital planes and at different inclinations, a network of satellites can cover the entire Earth's surface. The satellites are placed in orbits that are not necessarily geostationary but have different inclinations and altitudes to ensure coverage at all latitudes.
The minimum requirement of three satellites is based on the principle of triangulation. By having at least three satellites positioned at different locations, it becomes possible to determine the position of a radio transmitter on Earth accurately. This triangulation technique allows for reliable communication and tracking of the transmitter's location.
By strategically placing and coordinating the orbits of multiple satellites, it is possible to achieve continuous radio communication coverage all around the Earth, ensuring reliable communication regardless of the location on the planet.