Near-equatorial orbit
A near-equatorial orbit is an orbit that lies close to the equatorial plane of the object orbited. Such an orbit has an inclination near 0°. On Earth, such orbits lie on the celestial equator, the great circle of the imaginary celestial sphere on the same plane as the equator of Earth. A geostationary orbit is a particular type of equatorial orbit, one which is geosynchronous. A satellite in a geostationary orbit appears stationary, always at the same point in the sky, to observers on the surface.
Equatorial orbits are also advantageous for several reasons. Sites near the Equator, such as the Guiana Space Centre in Kourou, French Guiana, make good locations for spaceports as they have a fastest rotational speed of any latitude, 460 m/s. The added velocity reduces the fuel needed to launch spacecraft to orbit. Since Earth rotates eastward, only launches eastward take advantage of this boost of speed. Westward launches, in fact, are especially difficult from the Equator because of the need to counteract the extra rotational speed.
Equatorial orbits offer other advantages, such as to communication: a spaceship in an equatorial orbit passes directly over an equatorial spaceport on every rotation, in contrast to the varying ground track of an inclined orbit.
Furthermore, launches directly into equatorial orbit eliminate the need for costly adjustments to a spacecraft's trajectory. The maneuver to reach the 5° inclination of the Moon's orbit from the 28° N latitude of Cape Canaveral was originally estimated to reduce the payload capacity of the Apollo Program's Saturn V rocket by as much as 80%.
