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Encyclopedia > Low Earth orbit
An orbiting cannon ball showing various sub-orbital and orbital possibilities.
An orbiting cannon ball showing various sub-orbital and orbital possibilities.

A Low Earth Orbit (LEO) is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km. Given the rapid orbital decay of objects below approximately 200 km, the commonly accepted definition for LEO is between 200 - 2000 km (124 - 1240 miles)[1][2] above the Earth's surface. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... A sub-orbital spaceflight (or sub-orbital flight) is a spaceflight that does not involve putting a vehicle into orbit. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... In mathematics, a locus (Latin for place, plural loci) is a collection of points which share a common property. ... This article is about Earth as a planet. ...

Contents

Orbital Characteristics

Objects in LEO encounter atmospheric drag in the form of gases in the thermosphere (approximately 80-500 km up) or exosphere (approximately 500 km and up), depending on orbit height. LEO is an orbit around Earth between the atmosphere and below the inner Van Allen radiation belt. The altitude is usually not less than 300 km because that would be impractical due to the larger atmospheric drag.-1... The thermosphere is the layer of the earths atmosphere directly above the mesosphere and directly below the exosphere. ... [fAgot png|thumb|200px|right|Atmosphere diagram showing the exosphere and other layers. ... Van Allen radiation belts The Van Allen Radiation Belt is a torus of energetic charged particles (plasma) around Earth, held in place by Earths magnetic field. ...


Equatorial Low Earth Orbits (ELEO) are a subset of LEO. These orbits, with low inclination to the Equator, allow rapid revisit times and have the lowest delta-v requirement of any orbit. Orbits with a high inclination angle are usually called polar orbits. General In general physics delta-v is simply the change in velocity. ... A satellite in a polar orbit passes above or nearly above both poles of the planet (or other celestial body) on each revolution. ...


Higher orbits include medium Earth orbit (MEO), sometimes called intermediate circular orbit (ICO), and further above, Geostationary orbit (GEO). Orbits higher than low orbit can lead to earlier failure of electronic components due to intense radiation and charge accumulation, while commercial devices such as laptops have been used successfully in LEO during manned flight. Meo (Hindi: मेव, Urdu: میو) is a prominent Muslim Rajput tribe from Northern India and Pakistan. ... Intermediate circular orbit (ICO), also called medium earth orbit (MEO), is used by satellites between the altitudes of low earth orbit (up to 1400 km) and geostationary orbit (ca. ... Geostationary orbit A geostationary orbit (GEO) is a geosynchronous orbit directly above the Earths equator (0° latitude), with orbital eccentricity of zero. ...


Human use

Upgrading the International Space Station.
Upgrading the International Space Station.
Mir space station breaking up in Earth's atmosphere over the South Pacific on 23 March 2001.
Mir space station breaking up in Earth's atmosphere over the South Pacific on 23 March 2001.

The International Space Station is in a LEO that varies from 319.6 km to 346.9 km above the Earth's surface. With the exeception of the Project Apollo missions to the Moon and suborbital test flights such as the early Project Mercury missions and the flights of the X-15 rocket plane, most manned spaceflights have been in LEO, including all Space Shuttle and various space station missions. Image File history File links Size of this preview: 800 × 530 pixelsFull resolution (3032 × 2007 pixel, file size: 990 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Size of this preview: 800 × 530 pixelsFull resolution (3032 × 2007 pixel, file size: 990 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The International Space Station (ISS) is a research facility currently being assembled in space. ... For the current mission, see STS-118 NASAs Space Shuttle, officially called Space Transportation System (STS), is the United States governments current manned launch vehicle. ... Space Shuttle Orbiter Atlantis (NASA Orbiter Vehicle Designation: OV-104) is one of the fleet of space shuttles belonging to the U.S. National Aeronautics and Space Administration (NASA). ... is the 170th day of the year (171st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... Image File history File linksMetadata Download high-resolution version (3032x2007, 3787 KB) Original description: S116-E-05983 (12 Dec. ... Image File history File linksMetadata Download high-resolution version (3032x2007, 3787 KB) Original description: S116-E-05983 (12 Dec. ... The Mir Spacestation breaking up in Earths atmosphere over the South Pacific. ... The Mir Spacestation breaking up in Earths atmosphere over the South Pacific. ... This article is about Mir, the Soviet space station. ... is the 82nd day of the year (83rd in leap years) in the Gregorian calendar. ... Year 2001 (MMI) was a common year starting on Monday (link displays the 2001 Gregorian calendar). ... The International Space Station (ISS) is a research facility currently being assembled in space. ... Project Apollo was a series of human spaceflight missions undertaken by the United States of America (NASA) using the Apollo spacecraft and Saturn launch vehicle, conducted during the years 1961 – 1975. ... Apparent magnitude: up to -12. ... Mercury program monument Project Mercury was the United States first manned spaceflight program. ... Description Role: Research Aircraft Crew: one, pilot Dimensions Length: 50. ... Human spaceflight is space exploration with a human crew, and possibly passengers (in contrast to unmanned space missions, which are remotely-controlled or robotic space probes). ... For the current mission, see STS-118 NASAs Space Shuttle, officially called Space Transportation System (STS), is the United States governments current manned launch vehicle. ... The International Space Station in 2007 A space station is an artificial structure designed for humans to live in outer space. ...


While a majority of artificial satellites are placed in LEO, where they travel at about 27,400 km/h (8 km/s), making one complete revolution around the Earth in about 90 minutes, many communication satellites require geostationary orbits, and move at the same angular velocity as the Earth rotates. Since it requires less energy to place a satellite into a LEO and the LEO satellite needs less powerful amplifiers for successful transmission, LEO is still used for many communication applications. Because these LEO orbits are not geostationary, a network (or "constellation") of satellites is required to provide continuous coverage. Lower orbits also aid remote sensing satellites because of the added detail that can be gained. Remote sensing satellites can also take advantage of sun-synchronous LEO orbits at an altitude of about 800km and near polar inclination. ENVISAT is one example of an Earth observation satellite that makes use of this particular type of LEO. An Earth observation satellite, ERS 2 In the context of spaceflight, satellites are objects which have been placed into orbit by human endeavor. ... U.S. military MILSTAR communications satellite A communications satellite (sometimes abbreviated to comsat) is an artificial satellite stationed in space for the purposes of telecommunications using radio at microwave frequencies. ... A geostationary orbit (abbreviated GEO) is a circular orbit in the Earths equatorial plane, any point on which revolves about the Earth in the same direction and with the same period as the Earths rotation. ... A group of electronic satellites working in concert is known as a satellite constellation. ... For the purported psychic ability to sense remotely, see Remote viewing right Synthetic aperture radar image of Death Valley colored using polarimetry In the broadest sense, remote sensing is the short or large-scale acquisition of information of an object or phenomenon, by the use of either recording or real... By analogy with the geosynchronous orbit, a heliosynchronous orbit is a heliocentric orbit of radius 24. ... The Envisat (Environmental Satellite) satellite is an Earth-observing satellite built by the European Space Agency. ...


Although the Earth's pull due to gravity in LEO is not much less than on the surface of the Earth, people and objects in orbit experience weightlessness due to the effects of freefall. Gravity is a force of attraction that acts between bodies that have mass. ... Astronauts on the International Space Station display an example of weightlessness. ... Freefall or free fall in the strict sense is the condition of acceleration which is due only to gravity. ...


Atmospheric and gravity drag associated with launch typically add 1,500-2,000 m/s to the Delta{v}, (delta-V) required to reach normal LEO orbital velocity of around 7,800 m/s. In astrodynamics, gravity drag is inefficiency encountered by a spacecraft thrusting while moving against a gravitational field. ... General In general physics delta-v is simply the change in velocity. ...


Space debris

The LEO environment is becoming congested with space debris which has caused a growing concern in recent years, since collisions at orbital velocities can be highly damaging or dangerous and can produce even more space debris in the process, called the Kessler Syndrome. The Space Control Center, part of United States Strategic Command (formerly the United States Space Command), currently tracks more than 8,500 objects larger than 10cm in LEO.[3] Space debris or orbital debris, also called space junk and space waste, are the objects in orbit around Earth created by man that no longer serve any useful purpose. ... The Kessler Syndrome is a scenario, proposed by NASA consultant Donald J. Kessler, in which the volume of space debris in Low Earth Orbit is so high that objects in orbit are frequently struck by debris, creating even more debris and a greater risk of further impacts. ... USSTRATCOM emblem The LeMay building United States Strategic Command (USSTRATCOM) is one of nine Unified Combatant Commands of the United States Department of Defense which controls the nuclear weapons assets of the United States military. ...


See also

The following is a list of types of orbits: // Box orbit Circular orbit Ecliptic orbit Elliptic orbit Highly Elliptical Orbit Graveyard orbit Hohmann transfer orbit Hyperbolic trajectory Inclined orbit Osculating orbit Parabolic trajectory Capture orbit Escape orbit Semi-synchronous orbit Subsynchronous orbit Synchronous orbit Geocentric orbit Geosynchronous orbit Geostationary orbit... Space Shuttle Atlantis launches on mission STS-71. ... Intermediate circular orbit (ICO), also called medium earth orbit (MEO), is used by satellites between the altitudes of low earth orbit (up to 1400 km) and geostationary orbit (ca. ... Highly Elliptical Orbit (HEO) is an elliptic orbit characterized by a relatively low-altitude perigee and an extremely high-altitude apogee. ... In astrodynamics the specific orbital energy (or vis-viva energy) of an orbiting body traveling through space under standard assumptions is the sum of its potential energy () and kinetic energy () per unit mass. ... The International Space Station (ISS) is a research facility currently being assembled in space. ... Reentry redirects here. ... A satellite telephone, satellite phone, or satphone is a mobile phone that communicates directly with orbiting communications satellites. ...

References

  1. ^ IADC Space Debris Mitigation Guidelines. Inter-Agency Space Debris Coordination Committee (15 Oct 2002).
  2. ^ NASA Safety Standard 1740.14, Guidelines and Assessment Procedures for Limiting Orbital Debris. Office of Safety and Mission Assurance (1 Aug 1995).
  3. ^ USSTRATCOM Space Control Fact Sheet

  Results from FactBites:
 
Low Earth orbit - Wikipedia, the free encyclopedia (427 words)
A low Earth orbit (LEO) is an orbit around Earth between the atmosphere and the Van Allen radiation belt, with a low angle of inclination.
Orbits higher than this are subject to early electronic failure because of intense radiation and charge accumulation.
Orbits with a higher inclination angle are usually called polar orbits.
BIGpedia - Earth - Encyclopedia and Dictionary Online (3432 words)
The Earth is approximately a slightly oblate spheroid, with an average diameter of approximately 12,742 km.
Thus from Earth the main apparent motion of celestial bodies in the sky (except meteors which are within the atmosphere and low orbiting satellites) is the movement to the west at a rate of 15 °/h = 15'/min, i.e.
As the Moon orbits Earth, different parts of its face are illuminated by the Sun, leading to the lunar phases: the dark part of the face is separated from the light part by the solar terminator.
  More results at FactBites »

 
 

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