An orbit is the curved path, usually in the form of an ellipse, that an object takes around the Earth when centrifugal force and gravity are the only forces acting on it.

Many factors that are important to the life of a spacecraft, such as the altitude and type of orbit, come into play before it launches. These calculations are made so as to place the craft in orbit at the correct speed. The space shuttle, for example, travels around the Earth at a speed of approximately 17,500 miles (28,200 kilometers) per hour. This speed brings about a centrifugal force that balances the force of gravity and keeps the spacecraft from plummeting back to Earth. The orbiting craft does not slow down because its altitude is great enough to keep it out of the atmosphere, which, by causing friction, would cause it to lose speed.

There are several types of orbits, the most common of which are polar, geosynchronous, sun-synchronous and inclined. A polar orbit brings a spacecraft near the north and south poles, enabling it to pass over every spot on the Earth's surface. A geosynchronous orbit's altitude and speed allow it to follow the rotation of the Earth and remain directly above specific point on the equator. A sun-synchronous orbit follows a north-south path; every time a craft on a sun-synchronous orbit passes overhead, the sun is always in the same position. While all types of orbits have an inclination (the angle between the equatorial plane and the satellite orbital plane), that of an inclined orbit lies between that of a polar orbit (90 degrees) and a geosynchronous orbit (zero degrees). Inclined orbits can be determined by a region of interest or the latitude of the launch site.