celestial mechanics Celestial mechanics is the branch of astronomy that deals with the motions of objects in outer space. Historically, celestial mechanics applies principles of physics (classical mechanics) to astronomical objects, such as stars and planets, to ...

, the term stationary orbit refers to an orbit around a planet or moon where the orbiting satellite or

spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...

remains orbiting over the same spot on the surface. From the ground, the satellite would appear to be standing still, hovering above the surface in the same spot, day after day. "Space Today Online - Answers To Your Questions", Spacetoday.org, 2010, webpage:
ST-Sats
In practice, this is accomplished by matching the rotation of the surface below, by reaching a particular altitude where the orbital speed almost matches the rotation below, in an equatorial orbit. As the speed decreases slowly, then an additional boost would be needed to increase the speed back to a matching speed, or a

retro-rocket A retrorocket (short for ''retrograde rocket'') is a rocket engine providing thrust opposing the motion of a vehicle, thereby causing it to decelerate. They have mostly been used in spacecraft, with more limited use in short-runway aircraft land ...

could be fired to slow the speed when too fast. The stationary-orbit region of space is known as the

Clarke Belt A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitude ...

, named after British science fiction writer

Arthur C. Clarke Sir Arthur Charles Clarke (16 December 191719 March 2008) was an English science-fiction writer, science writer, futurist, inventor, undersea explorer, and television series host. He co-wrote the screenplay for the 1968 film '' 2001: A Spac ...

, who published the idea in ''

Wireless World ''Electronics World'' (''Wireless World'', founded in 1913, and in September 1984 renamed ''Electronics & Wireless World'') is a technical magazine in electronics and RF engineering aimed at professional design engineers. It is produced monthly in ...

'' magazine in 1945. A stationary orbit is sometimes referred to as a "fixed orbit".

Stationary Earth orbit

Around the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

, stationary satellites orbit at altitudes of approximately . Writing in 1945, the science-fiction author

imagined

communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. C ...

s as travelling in stationary orbits, where those satellites would travel around the Earth at the same speed the globe is spinning, making them hover stationary over one spot on the Earth's surface. A satellite being propelled into place, into a stationary orbit, is first fired to a special equatorial orbit called a "

geostationary transfer orbit A geosynchronous transfer orbit or geostationary transfer orbit (GTO) is a type of geocentric orbit. Satellite, Satellites that are destined for geosynchronous orbit, geosynchronous (GSO) or geostationary orbit (GEO) are (almost) always put into ...

" (GTO). Within this oval-shaped (

elliptical Elliptical may mean: * having the shape of an ellipse, or more broadly, any oval shape ** in botany, having an elliptic leaf shape ** of aircraft wings, having an elliptical planform * characterised by ellipsis (the omission of words), or by conc ...

) orbit, the satellite will alternately swing out to high and then back down to an altitude of only above the Earth (223 times closer). Then, at a planned time and place, an attached "kick motor" will push the satellite out to maintain an even, circular orbit at the 22,300-mile altitude.

Stationary Mars orbit

An ''areostationary orbit'' or ''areosynchronous equatorial orbit'' (abbreviated ''AEO'') is a circular areosynchronous orbit in the

Martian Mars, the fourth planet from the Sun, has appeared as a setting in works of fiction since at least the mid-1600s. It became the most popular celestial object in fiction in the late 1800s as the Moon was evidently lifeless. At the time, the pred ...

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 projectio ...

about from the centre of mass of Mars, any point on which revolves about Mars in the same direction and with the same

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

as the Martian surface. Areostationary orbit is a concept similar to Earth's geostationary orbit. The prefix ''areo-'' derives from

Ares Ares (; grc, Ἄρης, ''Árēs'' ) is the Greek god of war and courage. He is one of the Twelve Olympians, and the son of Zeus and Hera. The Greeks were ambivalent towards him. He embodies the physical valor necessary for success in war b ...

, the ancient Greek god of war and counterpart to the Roman god Mars, with whom the planet was identified. The modern Greek word for Mars is ().

References

{{Reflist Orbits Astrophysics Spaceflight concepts

Stationary Earth orbit

Stationary Mars orbit

See also

References