Editing Geosynchronous orbit (section)

==Properties==
[[File:Geosynchronous no geostationary orbit.gif|thumb|The orbit of a geosynchronous satellite at an inclination, from the perspective of an off-Earth observer ([[Earth-centered inertial|ECI]]) and of an observer rotating around the Earth at its spin rate ([[ECEF]]).]]

A geosynchronous orbit has the following properties:

* Period: 1436 minutes (one [[sidereal day]])
* [[Semi-major and semi-minor axes#Astronomy|Semi-major axis]]: 42,164&nbsp;km<ref name="smad"/>{{rp|121}}

===Period===
All geosynchronous orbits have an orbital period equal to exactly one sidereal day.<ref>{{cite book |editor-first1=Vladimir|editor-last1=Chobotov |year=1996 |title=Orbital Mechanics |publisher=AIAA Education Series |page=304|edition=2nd|location=Washington, DC|isbn=9781563471797|oclc=807084516}}</ref> This means that the satellite will return to the same point above the Earth's surface every (sidereal) day, regardless of other orbital properties.<ref>
{{cite book |title=Fundamentals of Astrodynamics and Applications |last=Vallado |first=David A. |year=2007 |publisher=Microcosm Press |location=Hawthorne, CA  |pages=31|oclc=263448232}}
</ref><ref name="smad"/>{{rp|121}} This orbital period, T, is directly related to the semi-major axis of the orbit through the formula:

: <math>T = 2\pi\sqrt{a^3 \over \mu}</math>

where:
: {{mvar|a}} is the length of the orbit's semi-major axis
: <math>\mu</math> is the [[standard gravitational parameter]] of the central body<ref name="smad"/>{{rp|137}}

===Inclination===
A geosynchronous orbit can have any inclination.

Satellites commonly have an inclination of zero, ensuring that the orbit remains over the equator at all times, making it stationary with respect to latitude from the point of view of a ground observer (and in the [[ECEF]] reference frame).<ref name="smad"/>{{rp|122}}

Another popular inclinations is 63.4° for a Tundra orbit, which ensures that the orbit's [[argument of perigee]] does not change over time.<ref name="scs"/>

===Ground track===

In the special case of a geostationary orbit, the [[ground track]] of a satellite is a single point on the [[equator]]. In the general case of a geosynchronous orbit with a non-zero [[inclination]] or [[Eccentricity (orbit)|eccentricity]], the ground track is a more or less distorted figure-eight, returning to the same places once per sidereal day.<ref name="smad"/>{{rp|122}}