Difference between revisions of "Perigee"
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The equivalent for [[periapsis]] of a body in Earth orbit is '''perigee''', also called '''perigee height'''. | The equivalent for [[periapsis]] of a body in Earth orbit is '''perigee''', also called '''perigee height'''. | ||
| − | Unlike with all other bodies, mission planners are usually more interested in the height above the surface for [[low Earth orbit]] spacecraft. Hence perigee height refers to the distance between the body and the Earth's surface rather than the distance between the body and the Earth's centre of mass, for all objects in Earth orbit.<ref name=Wertz>J.R. Wertz - ''Orbits and astrodynamics'' in J.R. Wertz, D.F. Everett & J.J. Puschell eds. ''Space mission engineering: The new SMAD'' ISBN 978-1-881883-15-9 p. 202</ref> | + | Unlike with all other bodies, mission planners are usually more interested in the height above the surface for [[low Earth orbit]] spacecraft. Hence perigee height refers to the distance between the body and the Earth's surface rather than the distance between the body and the Earth's centre of mass, for all objects in Earth orbit.<ref name=Wertz>J.R. Wertz - ''Orbits and astrodynamics'' in J.R. Wertz, D.F. Everett & J.J. Puschell eds. ''Space mission engineering: The new SMAD'' ISBN 978-1-881883-15-9 p. 202</ref> This does not occur because the word perigee is special in some way, but rather because frequent inaccurate usage has effectively shortened perigee height to perigee and replaced the other meaning. |
If you wish to anambiguously use the same measurements as with all other bodies, it is best to say [[perifocal distance]] rather than perigee. | If you wish to anambiguously use the same measurements as with all other bodies, it is best to say [[perifocal distance]] rather than perigee. | ||
| − | The | + | The distance where a body's orbit is farthest from the Earth is known as [[apogee]]. |
==References== | ==References== | ||
Revision as of 02:51, 22 February 2013
Definition
The equivalent for periapsis of a body in Earth orbit is perigee, also called perigee height.
Unlike with all other bodies, mission planners are usually more interested in the height above the surface for low Earth orbit spacecraft. Hence perigee height refers to the distance between the body and the Earth's surface rather than the distance between the body and the Earth's centre of mass, for all objects in Earth orbit.[1] This does not occur because the word perigee is special in some way, but rather because frequent inaccurate usage has effectively shortened perigee height to perigee and replaced the other meaning.
If you wish to anambiguously use the same measurements as with all other bodies, it is best to say perifocal distance rather than perigee.
The distance where a body's orbit is farthest from the Earth is known as apogee.
References
- ↑ J.R. Wertz - Orbits and astrodynamics in J.R. Wertz, D.F. Everett & J.J. Puschell eds. Space mission engineering: The new SMAD ISBN 978-1-881883-15-9 p. 202
