MathDB

A satellite is considered accessible from the point

A{}

of the planet's surface if it is located relative to the tangent plane drawn at point

A{}

, strictly on the other side than the planet. What is the smallest number of satellites that need to be launched over a spherical planet so that at some point the signals of at least two satellites are available from each point on the planet's surface?
Proposed by S. Volchenkov

Problem Statement