Satellite

A satellite is an object that orbits a larger body. Natural satellites form without human construction; artificial satellites are built and placed in orbit.

Orbital mechanics: The study of the motion of bodies under gravity, including spacecraft and planets. It describes the gravitational paths that satellites follow.
Global Positioning System: A satellite-based navigation system that provides position and timing information worldwide. Its constellation lets receivers calculate location from signals sent by orbiting satellites.
Newton's cannonball: A thought experiment showing how a projectile launched fast enough could orbit Earth. It illustrates the basic idea behind placing an artificial object in orbit.
Space Age: The period of space exploration and technology that began with the first artificial satellites in the 1950s. Satellite launches opened the era of sustained human activity in space.
Planet: A celestial body that orbits a star, is nearly round under its own gravity, and meets a standard orbital-clearing criterion. Planets orbit stars, while satellites orbit planets or other larger bodies.
Kepler's laws of planetary motion: Three laws describing how orbiting bodies move around a central mass. They approximate satellite orbits and relate orbital size to period.
Weather satellite: An artificial satellite designed to observe atmospheric conditions and weather systems. Its images and measurements track clouds, storms, and changing climate patterns.
Arthur C. Clarke: A British science-fiction writer and scientist who proposed geostationary communications satellites in 1945. His proposal anticipated a major use of artificial satellites.
Space debris: Nonfunctional human-made objects and fragments that remain in orbit around Earth. Accumulating debris threatens operating satellites and complicates future missions.
Moon: A natural satellite that orbits a planet or another body larger than itself. The word often means Earth's natural satellite, unlike artificial satellites.

Linked from 7 pages