A near-equatorial orbit is an orbit that lies close to the

equatorial plane The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth. This plane of reference bases the equatorial coordinate system. In other words, the celestial equator is an abstract projecti ...

of the object orbited. Such an orbit has an

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

near 0°. On Earth, such orbits lie on the

celestial equator The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth. This plane of reference bases the equatorial coordinate system. In other words, the celestial equator is an abstract proj ...

, 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 geosynchronous orbit (sometimes abbreviated GSO) is an Earth-centered orbit with an orbital period that matches Earth's rotation on its axis, 23 hours, 56 minutes, and 4 seconds (one sidereal day). The synchronization of rotation and orbital ...

. A satellite in a geostationary orbit appears stationary, always at the same point in the sky, to observers on the surface of the Earth. Equatorial orbits can be advantageous for several reasons. For launches of human technology to space, sites near the Equator, such as the

Guiana Space Centre The Guiana Space Centre (french: links=no, Centre spatial guyanais; CSG), also called Europe's Spaceport, is a European spaceport to the northwest of Kourou in French Guiana, a region of France in South America. Kourou is located approximatel ...

Kourou Kourou () is a commune in French Guiana, an overseas region and department of France in South America. Kourou is famous for being the location of the Guiana Space Centre, the main spaceport of France and the European Space Agency (ESA). It i ...

French Guiana French Guiana ( or ; french: link=no, Guyane ; gcr, label=French Guianese Creole, Lagwiyann ) is an overseas department/region and single territorial collectivity of France on the northern Atlantic coast of South America in the Guianas. ...

, or Alcantara Launch Centre in Brazil, can be good locations for

spaceport A spaceport or cosmodrome is a site for launching or receiving spacecraft, by analogy to a seaport for ships or an airport for aircraft. The word ''spaceport'', and even more so ''cosmodrome'', has traditionally been used for sites capable ...

s as they provide some additional

orbital speed In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter or, if one body is much more mas ...

to the

launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload ( spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pads, supported by a launch control center and ...

by imparting the

rotational speed Rotational frequency (also known as rotational speed or rate of rotation) of an object rotating around an axis is the frequency of rotation of the object. Its unit is revolution per minute (rpm), cycle per second (cps), etc. The symbol fo ...

of the Earth, 460 m/s, to the spacecraft at launch. The added

velocity Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity i ...

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 A ground track or ground trace is the path on the surface of a planet directly below an aircraft's or satellite's trajectory. In the case of satellites, it is also known as a suborbital track, and is the vertical projection of the satellite's ...

of an inclined orbit. Furthermore, launches directly into equatorial orbit eliminate the need for costly adjustments to a spacecraft's launch trajectory. The maneuver to reach the 5° inclination of the Orbit of the Moon, Moon's orbit from the 28° N latitude of Cape Canaveral was originally estimated to reduce the payload capacity of the Apollo Program, Apollo Program's Saturn V rocket by as much as 80%.

Non-inclined orbit

A non-inclined orbit is an orbit coplanar with a plane of reference. The orbital inclination is 0° for prograde orbits, and pi, π (180°) for retrograde motion, retrograde ones. If the plane of reference is a massive spheroid body's equatorial plane, these orbits are called equatorial, and the non-inclined orbit is merely a special case of the near-equatorial orbit. However, a non-inclined orbit need not be referenced only to an equatorial reference plane. If the plane of reference is the ecliptic plane, they are called an ecliptic orbit. As non-inclined orbits lack orbital nodes, nodes, the ascending node is usually taken to lie in the reference direction (usually the Equinox (celestial coordinates), vernal equinox), and thus the longitude of the ascending node is taken to be zero. Also, the argument of periapsis is undefined. A geostationary orbit is a geosynchronous orbit, geosynchronous example of an equatorial orbit, non-inclined orbit that is coplanar with the equator of Earth.

References

Astrodynamics Orbits {{astronomy-stub

Non-inclined orbit

See also

References