Artificial satellites are spacecraft that maintain an orbit around a celestial body. What differentiates an orbit from other types of space flight is it doesn't require any additional propulsion. Satellites can hold a number of different orbits. One type is a polar orbit, which causes the spacecraft to pass over the north and south poles. Another is an equatorial orbit, which causes the satellite to circle the Earth's equator. The farther the orbit from the surface of the earth, the longer it takes to complete a circuit of the earth. If the vessel uses an equatorial orbit at a distance of 22,300 miles from Earth, it can achieve geo-synchronous orbit, which causes the satellite to remain stationary over a specific area. The first satellite was the Soviet Union vehicle Sputnik 1, which was launched in October 1957. Today satellites fulfill many roles, including scientific research, weather forecasting, personal and business communication, and military intelligence gathering.