Satellites for Internet Communication

摘要

Orbiting satellites were first considered centuries ago in a famous problem solved by Sir Isaac Newton himself. He first posed the artificial Earth-orbiting satellite scenario in Mathematical Principals of Natural Philosophy published in 1687. He imagined that a cannon could shoot a projectile to circumnavigate the globe and envisioned that at a sufficiently high radial velocity, the projectile would have a higher radial velocity than falling velocity and hence would always miss the Earth, staying on a circular path about the Earth. At low orbit the projectile's velocity must be greater than that of the rotating Earth's radial velocity. But as the projectile goes into a higher orbit, the velocity necessary to stay in orbit decreases, until at 22,300 miles above the Earth's surface, the velocity of the projectile matches exactly that of Earth. In this orbit we have geo-sta-tionary orbit, that is, the satellite remains above a fixed point on the Earth.