Soldier: Created polar orbit

2023-09-10T12:52:24Z

Created polar orbit

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{{short description|Satellite orbit with high inclination}}
[[File:Polar orbit.ogv|thumb|200px|Polar orbit]]
A '''polar orbit''' is one in which a [[satellite]] [[pass (spaceflight)|pass]]es above or nearly above both [[Poles of astronomical bodies|poles]] of the body being [[orbit]]ed (usually a planet such as the [[Earth]], but possibly another body such as the [[Moon]] or [[Sun]]) on each revolution. It has an [[inclination]] of about 60–90 [[Degree (angle)|degree]]s to the body's [[equator]].<ref name="esa">{{cite web |url = http://www.esa.int/Enabling_Support/Space_Transportation/Types_of_orbits |title=ESA - Types of Orbits |date=2020-03-30 |access-date=2021-01-10}}</ref>

Launching [[satellite]]s into polar orbit requires a larger [[launch vehicle]] to launch a given payload to a given altitude than for a [[near-equatorial orbit]] at the same altitude, because it cannot take advantage of the [[Earth's rotation]]al [[velocity]]. Depending on the location of the [[Spaceport|launch site]] and the [[Orbital_inclination|inclination]] of the polar orbit, the launch vehicle may lose up to 460 m/s of [[Delta-v]], approximately 5% of the Delta-v required to attain [[Low Earth orbit]].

==Usage==
Polar orbits are used for [[Earth observation satellite|Earth-mapping]], [[reconnaissance satellite]]s, as well as for some [[weather satellite]]s.<ref>Science Focus 2nd Edition 2, pg. 297</ref>
The [[Iridium satellite constellation]] uses a polar orbit to provide telecommunications services.

{{anchor|nearPolarOrbit}}Near-polar orbiting satellites commonly choose a [[Sun-synchronous orbit]], where each successive orbital [[pass (spaceflight)|pass]] occurs at the same local time of day. For some applications, such as remote sensing, it is important that ''changes'' over time are not aliased by changes in local time. Keeping the same local time on a given pass requires that the [[frequency|time period]] of the orbit be kept as short, which requires a low orbit. However, very low orbits rapidly [[orbital decay|decay]] due to [[drag (physics)|drag]] from the atmosphere. Commonly used [[altitude]]s are between 700 and 800 km, producing an [[orbital period]] of about 100 minutes.<ref name="phy6">{{cite web |url=http://www.phy6.org/Education/wlopolar.html |title=Polar Orbiting Satellites |first=David P. |last=Stern |date=2001-11-25 |access-date=2009-01-21}}</ref> The half-orbit on the Sun side then takes only 50 minutes, during which local time of day does not vary greatly.

{{anchor|precessingSV}}To retain a Sun-synchronous orbit as the [[Earth's orbit|Earth revolves]] around the Sun during the year, the orbit must [[Nodal precession|precess]] about the Earth at the same rate (which is not possible if the satellite passes directly over the pole).
Because of Earth's [[equatorial bulge]], an orbit [[orbital inclination|inclined]] at a slight angle is subject to a [[torque]], which causes [[precession]]. An angle of about 8° from the pole produces the desired precession in a 100-minute orbit.<ref name="phy6" />

==See also==
*[[List of orbits]]
*[[Molniya orbit]]
*[[Tundra orbit]]
*[[Vandenberg Air Force Base]], a major United States launch location for polar orbits

==References==
{{reflist}}

==External links==
* [https://web.archive.org/web/20120204054322/http://www.braeunig.us/space/orbmech.htm Orbital Mechanics] (Rocket and Space Technology)

{{orbits}}

{{DEFAULTSORT:Polar Orbit}}
[[Category:Astrodynamics]]
[[Category:Earth orbits]]
[[Category:Articles containing video clips]]

Polar orbit - Revision history

Soldier: Created polar orbit