Geocentric Orbit

Information about Geocentric Orbit

A geocentric orbit is an orbit of any object orbiting the Earth, such as the Moon or artificial satellites. Currently there are approximately 2465 artificial satellites orbiting the Earth and 6216 pieces of space debris as tracked by the Goddard Space Flight Center. Over 16,291 previously launched objects have decayed into the Earth's atmosphere.

List of terms and concepts

The following words may have more than one definition or other non-Earth specific definition(s).
In the spirit of brevity some of the definitions have been altered or truncated to reflect only their usage on this page.

Analemma: a term in astronomy used to describe the plot of the positions of the Sun on the celestial sphere throughout one year. Closely resembles a figure-eight.

Altitude: as used here, the height of an object above the average surface of the Earth's oceans.

Eccentricity: a measure of how much an orbit deviates from a perfect circle. Eccentricity is strictly defined for all circular, elliptic, parabolic and hyperbolic orbits.

Equatorial plane: as used here, an imaginary plane extending from the equator on the Earth to the celestial sphere.

Orbital characteristics: the six parameters of the Keplerian elements needed to specify that orbit uniquely.

Escape velocity: as used here, the minimum velocity an object without propulsion needs to have to move away indefinitely from the earth. An object with such a velocity will enter an escape orbit.

Impulse: the product of a force and the time during which it acts. Measured in (kg m/s or N·s).

Inclination: the angle between a reference plane and another plane or axis. In the sense discussed here the reference plane is the Earth's equatorial plane.

Orbital period: as defined here, time it takes a satellite to make one full orbit about the Earth.

Sidereal day: the time it takes for a celestial object to rotate 360°. For the Earth this is: 23 hours, 56 minutes, 4.091 seconds.

Solar time: as used here, the local time as measured by a sundial.

Velocity: an object's speed in a particular direction. Since velocity is defined as a vector, both speed and direction are required to define it.

Geocentric orbit types

The following is a list of different geocentric orbit classifications.

Altitude classifications

Low Earth Orbit (LEO) - Geocentric orbits ranging in altitude from 0 - 2000 km (0 - 1240 miles); one revolution takes 90 minutes, the speed is 8 km/s.

Medium Earth Orbit (MEO) - Geocentric orbits ranging in altitude from 2000 km - to just below geosynchronous orbit at 35,786 km (22,240 miles). Also known as an intermediate circular orbit.

Highly Elliptical Orbit (HEO) - Geocentric orbits with a high apogee and low perigee that result in long dwell times near perigee.

Geosynchronous Orbit (GEO) - Geocentric orbit with an altitude of 35,786 km (22,236 statute miles) above mean sea level. The period of the orbit coincides with the rotation period of the earth: 24 hours; the speed is 3 km/s.

Inclination classifications

Inclined Orbit - An orbit whose inclination in reference to the equatorial plane is not 0.

::Polar Orbit - A satellite that passes above or nearly above both poles of the planet on each revolution. Therefore it has an inclination of (or very close to) 90 degrees.

::Polar Sun-synchronous Orbit - A nearly polar orbit that passes the equator at the same local time on every pass. Useful for image taking satellites because shadows will be the same on every pass.

Eccentricity classifications

Circular Orbit - An orbit that has an eccentricity of 0 and whose path traces a circle.

:Hohmann transfer orbit - An orbital maneuver that moves a spacecraft from one circular orbit to another using two engine impulses. This maneuver was named after Walter Hohmann.

Elliptic Orbit - An orbit with an eccentricity greater than 0 and less than 1 whose orbit traces the path of an ellipse.

:Geosynchronous Transfer Orbit - A geocentric-elliptic orbit where the perigee is at the altitude of a Low Earth Orbit (LEO) and the apogee at the altitude of a geosynchronous orbit.

:Geostationary Transfer Orbit - A geocentric-elliptic orbit where the perigee is at the altitude of a Low Earth Orbit (LEO) and the apogee at the altitude of a geostationary orbit.

:Molniya Orbit - A highly elliptical orbit with inclination of 63.4° and orbital period of ½ of a sidereal day (roughly 12 hours). Such a satellite spends most of its time over a designated area of the planet.

:Tundra Orbit - A highly elliptical orbit with inclination of 63.4° and orbital period of one sidereal day (roughly 24 hours). Such a satellite spends most of its time over a designated area of the planet.

Hyperbolic orbit - An orbit with the eccentricity greater than 1. Such an orbit also has a velocity in excess of the escape velocity and as such, will escape the gravataional pull of the planet and continue to travel infinitely.

Parabolic Orbit - An orbit with the eccentricity equal to 1. Such an orbit also has a velocity equal to the escape velocity and therefore will escape the gravatational pull of the planet and travel until it's velocity relative to the planet is 0. If the speed of such an orbit is increased it will become a hyperbolic orbit.

:Escape Orbit (EO) - A high-speed parabolic orbit where the object has escape velocity and is moving away from the planet.

:Capture Orbit - A high-speed parabolic orbit where the object has escape velocity and is moving toward the planet.

Directional classifications

Prograde orbit - an orbit in which the projection of the object onto the equatorial plane revolves about the Earth in the same direction as the rotation of the Earth.

Retrograde orbit - an orbit in which the projection of the object onto the equatorial plane revolves about the Earth in the direction opposite that of the rotation of the Earth.

Geosynchronous classifications

Semi-Synchronous Orbit (SSO) - An orbit with an altitude of approximately 20,200 km (12544.2 miles) and an orbital period of approximately 12 hours

Geosynchronous Orbit (GEO) - Orbits with an altitude of approximately 35,786 km (22,240 miles). Such a satellite would trace an analemma (figure 8) in the sky.

::Geostationary orbit (GSO): A geosynchronous orbit with an inclination of zero. To an observer on the ground this satellite would appear as a fixed point in the sky.

::Clarke Orbit - Another name for a geostationary orbit. Named after the writer Arthur C. Clarke.

::Supersynchronous orbit - A disposal / storage orbit above GSO/GEO. Satellites will drift west.

::Subsynchronous orbit - A drift orbit close to but below GSO/GEO. Satellites will drift east.

::Graveyard Orbit - An orbit a few hundred kilometers above geosynchronous that satellites are moved into at the end of their operation.

:::Disposal Orbit - A synonym for graveyard orbit.

:::Junk Orbit - A synonym for graveyard orbit.

Special classifications

Sun-synchronous Orbit - An orbit which combines altitude and inclination in such a way that the satellite passes over any given point of the planet's surface at the same local solar time. Such an orbit can place a satellite in constant sunlight and is useful for imaging, spy, and weather satellites.

Moon Orbit - The orbital characteristics of Earth's Moon. Average altitude of 384,403 kilometres (238,857 mi), elliptical-inclined orbit.

Non-geocentric classifications

Horseshoe Orbit - An orbit that appears to a ground observer to be orbiting a planet but is actually in co-orbit with it. See asteroids 3753 (Cruithne) and 2002 AA₂₉.

Exo-orbit - A maneuver where a spacecraft approaches the height of orbit but lacks the velocity to sustain it.

:Sub-Orbital Spaceflight - A synonym for Exo-orbit.

Earth orbits

orbit	center-to-center distance	altitude above the Earth's surface	speed	period/time in space	specific orbital energy
minimum sub-orbital spaceflight (vertical)	6500 km	100 km	0.0 km/s	just reaching space	1.0 MJ/kg
ICBM	up to 7600 km	up to 1200 km	6 to 7 km/s	time in space: 25 min	27 MJ/kg
LEO	6,600 to 8,400 km	200 to 2000 km	circular orbit: 6.9 to 7.8 km/s elliptic orbit: 6.5 to 8.2 km/s	89 to 128 min	32.1 to 38.6 MJ/kg
Molniya orbit	6,900 to 46,300 km	500 to 39,900 km	1.5 to 10.0 km/s	11 h 58 min	54.8 MJ/kg
GEO	42,000 km	35,600 km	3.1 km/s	23 h 56 min	57.5 MJ/kg
Orbit of the Moon	363,000 to 406,000 km	357,000 to 399,000 km	0.97 to 1.08 km/s	27.3 days	61.8 MJ/kg

References

Satellite Situation Report. NASA Goddard Space Flight Center (2000-02-01). Retrieved on 2006-09-10.
http://www.freemars.org/jeff/speed/index.htm
http://www.tech-faq.com/medium-earth-orbit.shtml
http://www.hq.nasa.gov/office/pao/History/conghand/traject.htm
http://www.space.com/scienceastronomy/solarsystem/second_moon_991029.html
http://www.astro.uwo.ca/~wiegert/3753/3753.html
http://www.astro.uwo.ca/~wiegert/AA29/AA29.html

• • [ e] Orbits
Orbit types	Box orbit • Circular orbit • Ecliptic orbit • Elliptic orbit • Highly Elliptical Orbit • Graveyard orbit • Hyperbolic trajectory • Inclined orbit • Osculating orbit • Parabolic trajectory • Capture orbit • Escape orbit • Semi-synchronous orbit • Subsynchronous orbit • Synchronous orbit • Parking orbit
Earth-centered orbits	Geosynchronous orbit • Geostationary orbit • Sun-synchronous orbit • Low Earth orbit • Medium Earth Orbit • Molniya orbit • Near equatorial orbit • Orbit of the Moon • Polar orbit • Tundra orbit
Other orbits	Areosynchronous orbit • Areostationary orbit • Halo orbit • Lissajous orbit • Lunar orbit • Heliocentric orbit • Heliosynchronous orbit
Orbital elements	Inclination ( $\text{[math]}$ ) • Longitude of the ascending node ( $\text{[math]}$ ) • Eccentricity ( $\text{[math]}$ ) • Argument of periapsis ( $\text{[math]}$ ) • Semi-major axis ( $\text{[math]}$ ) • Mean anomaly at epoch ( $\text{[math]}$ )
Other orbital parameters	True anomaly ( $\text{[math]}$ ) • Semi-minor axis ( $\text{[math]}$ ) • Linear eccentricity ( $\text{[math]}$ ) • Eccentric anomaly ( $\text{[math]}$ ) • Mean longitude ( $\text{[math]}$ ) • True longitude ( $\text{[math]}$ ) • Orbital period ( $\text{[math]}$ )
Orbital maneuvers	Bi-elliptic transfer • Geostationary transfer orbit • Gravitational slingshot • Hohmann transfer orbit • Orbital inclination change • Orbit phasing • Space rendezvous
Other orbital mechanics topics	Apsis • Celestial coordinate system • Delta-v budget • Epoch • Ephemeris • Equatorial coordinate system • Gravity turn • Ground track • Interplanetary Transport Network • Kepler's laws of planetary motion • Lagrangian point • List of orbits • n-body problem • Orbit equation • Orbital state vectors • Perturbation • Retrograde and direct motion • Specific orbital energy • Specific relative angular momentum • The Oberth effect

Orbit usually refers to the concept in celestial mechanics.

Specific types of orbit:

Artificial satellite orbit
Circular orbit
Disposal orbit
Earth orbit
Elliptic orbit
Geocentric orbit
Geostationary orbit
Geosynchronous orbit

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EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001. Their greatest hit, their debut single "time after time", peaked at #13 in the Oricon singles chart.
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Moon

The Moon as seen by an observer on Earth
Orbital characteristics
Periapsis: 363,104 km
0.0024 AU
Apoapsis: 405,696 km
0.0027 AU
Semi-major axis: 384,399 km
0.
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satellite is an object which has been placed into orbit by human endeavor. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon.
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Orbit usually refers to the concept in celestial mechanics.

Specific types of orbit:

Artificial satellite orbit
Circular orbit
Disposal orbit
Earth orbit
Elliptic orbit
Geocentric orbit
Geostationary orbit
Geosynchronous orbit

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Space debris or orbital debris, also called space junk and space waste, are the objects in orbit around Earth created by humans, that no longer serve any useful purpose.
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Goddard Space Flight Center (GSFC) is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately 6.5 miles northeast of Washington, D.C.
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Atmospheric reentry is the process by which vehicles that are outside the atmosphere of a planet can enter that atmosphere and reach the planetary surface intact. Vehicles that undergo this process include spacecraft from orbit, vehicles coming straight from other space bodies, as
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atmosphere is a layer of gases that may surround a material body of sufficient mass.^[1] The gases are attracted by the gravity of the body, and are retained for a longer duration if gravity is high and the atmosphere's temperature is low.
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In mathematics, truncation is the term for limiting the number of digits right of the decimal point, by discarding the least significant ones.

For example, consider the real numbers

5.6341432543653654

32.438191288

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analemma (pronounced IPA: /ˌænəˈlɛmə/, Latin for the pedestal of a sundial) is a curve representing the angular offset of a celestial body (usually the Sun) from its mean position
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Astronomy is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation).
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chart or graph is a type of information graphic or graphic organizer that represents tabular numeric data and/or functions. Charts are often used to make it easier to understand large quantities of data and the relationship between different parts of the data.
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The Sun

Observation data
Mean distance
from Earth 1.49610¹¹ m
(8.31 min at light speed)
Visual brightness (V) −26.74^m ^[1]
Absolute magnitude 4.
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celestial sphere is an imaginary rotating sphere of "gigantic radius", concentric and coaxial with the Earth. All objects in the sky can be thought of as lying upon the sphere.
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For other uses see Altitude (disambiguation)

Altitude is the elevation of an object from a known level or datum (plural: data). Common data are mean sea level and the surface of the WGS-84 geoid, used by GPS.
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Height is the measurement of vertical distance, but has two meanings in common use. It can either indicate how "tall" something is, or how "high up" it is. For example one could say "That is a tall building", or "That airplane is high up in the sky".
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In mathematics, an average, or central tendency of a data set refers to a measure of the "middle" or "expected" value of the data set. There are many different descriptive statistics that can be chosen as a measurement of the central tendency of the data items.
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Earth's oceans
(World Ocean)

Arctic Ocean
Atlantic Ocean
Indian Ocean
Pacific Ocean
Southern Ocean

An ocean (from Ωκεανός, Okeanos
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eccentricity, denoted e or , is a parameter associated with every conic section. It can be thought of as a measure of how much the conic section deviates from being circular.

In particular,

The eccentricity of a circle is zero.

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ORBit is a CORBA compliant Object Request Broker (ORB). The current version is called ORBit2 and is compliant with CORBA version 2.4. It is developed under the GPL license and is used as middleware for the GNOME project.
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A deviation is a difference or the (real or metaphorical) route followed by a different choice.

Deviation can refer to:

Deviation (statistics), the difference between the value of an observation and the mean of the population in mathematics and statistics.

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circle is the set of all points in a plane at a fixed distance, called the radius, from a given point, the centre.

Circles are simple closed curves which divide the plane into an interior and exterior.
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Eccentricity may refer to:

Eccentricity (behavior), unusual or odd behavior on the part of a person, as opposed to being "normal"
Eccentricity (mathematics), a parameter associated with every conic section
Eccentricity vector

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For other meanings of the term "orbit", see orbit (disambiguation)

In astrodynamics or celestial mechanics a circular orbit is an elliptic orbit with the eccentricity equal to 0.
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elliptic orbit can be computed from the Vis-viva equation as:

where:

is standard gravitational parameter,
is radial distance of orbiting body from central body,
is length of semi-major axis.

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In astrodynamics or celestial mechanics a parabolic trajectory is an orbit with the eccentricity equal to 1. When moving away from the source it is called an escape orbit, otherwise a capture orbit.
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In astrodynamics or celestial mechanics a hyperbolic trajectory is an orbit with the eccentricity greater than 1. Under standard assumptions a body traveling along this trajectory will coast to infinity, arriving there with hyperbolic excess velocity relative to the central body.
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Geocentric Orbit

Information about Geocentric Orbit

List of terms and concepts

Geocentric orbit types

Altitude classifications

Inclination classifications

Eccentricity classifications

Directional classifications

Geosynchronous classifications

Special classifications

Non-geocentric classifications

Earth orbits

See also

References