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. In Physics, an orbit is the gravitationally curved path of one object around a point or another body for example the gravitational orbit of a planet around a star In Mathematics, a locus ( Latin for "place" plural loci) is a collection of points which share a property Given the rapid orbital decay of objects below approximately 200 km, the commonly accepted definition for LEO is between 160 - 2000 km (100 - 1240 miles) above the Earth's surface. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 [1][2]
With the exception of the lunar flights of the Apollo program, and the sub-orbital flights of the X-15 and SpaceShipOne rocket planes, all human spaceflights have been in LEO, including all Space Shuttle and space station missions. A sub-orbital spaceflight (or sub-orbital flight is a Spaceflight in which the Spacecraft reaches space, but its Trajectory intersects SpaceShipOne is a Spaceplane that completed the first privately funded Human spaceflight on June 21, 2004. A rocket-powered aircraft or rocket plane is an Aircraft that uses a Rocket for propulsion sometimes in addition to airbreathing Jet engines A human spaceflight is a Spaceflight with a human crew, and possibly passengers NASA 's Space Shuttle, officially called the Space Transportation System ( STS) is the Spacecraft currently used by the United States A space station is an artificial structure designed for Humans to live in Outer space.
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. This page is about the physical properties of gas as a state of matter The thermosphere is the layer of the Earth's atmosphere directly above the Mesosphere and directly below the Exosphere. The exosphere is the uppermost layer of the atmosphere. On Earth, its lower boundary at the edge of the Thermosphere is estimated to be 500 km to LEO is an orbit around Earth between the atmosphere and below the inner Van Allen radiation belt. The Van Allen radiation belt is a Torus of energetic Charged particles ( plasma) around Earth, held in place by Earth's Magnetic The altitude is usually not less than 300 km because that would be impractical due to the larger atmospheric drag.
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. In Astrodynamics, the term delta-v, literally "change in velocity" (see symbol delta) has a specific meaning it is a Scalar which takes Orbits with a high inclination angle are usually called polar orbits. A polar orbit is an Orbit in which a Satellite passes above or nearly above both poles of the body (usually a planet such as the Earth, but possibly
Higher orbits include medium Earth orbit (MEO), sometimes called intermediate circular orbit (ICO), and further above, Geostationary orbit (GEO). Medium Earth Orbit (MEO, sometimes called Intermediate Circular Orbit (ICO is the region of space around the Earth above low Earth orbit ( and below Geostationary orbit Medium Earth Orbit (MEO, sometimes called Intermediate Circular Orbit (ICO is the region of space around the Earth above low Earth orbit ( and below Geostationary orbit A geostationary orbit (GEO is a Geosynchronous orbit directly above the Earth 's Equator (0° Latitude) with a period equal to the Earth's 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.
Human use
The International Space Station is in a LEO that varies from 319. 6 km (199 mi) to 346. 9 km (216 mi) above the Earth's surface. [3]
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. This article is about artificial satellites For natural satellites also known as moons see Natural satellite. A communications satellite (sometimes abbreviated to comsat) is an artificial Satellite stationed in space for the purposes of Telecommunications. A geostationary orbit (GEO is a Geosynchronous orbit directly above the Earth 's Equator (0° Latitude) with a period equal to the Earth's 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. A group of electronic Satellites working in concert is known as a satellite constellation. Lower orbits also aid remote sensing satellites because of the added detail that can be gained. Remote sensing is the small or large-scale acquisition of information of an object or phenomenon by the use of either recording or real-time sensing device(s that is not in physical Remote sensing satellites can also take advantage of sun-synchronous LEO orbits at an altitude of about 800 km (500 mi) and near polar inclination. This article is about a class of orbits about the Earth For a class of orbits around the sun see Heliosynchronous orbit. ENVISAT is one example of an Earth observation satellite that makes use of this particular type of LEO. Envisat (Environmental 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. Gravitation is a natural Phenomenon by which objects with Mass attract one another Weightlessness is a phenomenon experienced by people during Free-fall. Free fall is motion with no Acceleration other than that provided by Gravity.
Atmospheric and gravity drag associated with launch typically add 1,500-2,000 m/s to the 
(delta-V) required to reach normal LEO orbital velocity of around 7,800 m/s (17,448 mph). In Astrodynamics and Rocketry, gravity drag (or gravity losses) is the difference between the Delta-v expended and the actual change in speed In Astrodynamics, the term delta-v, literally "change in velocity" (see symbol delta) has a specific meaning it is a Scalar which takes
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. Space debris or orbital debris, also called space junk and space waste are the objects in Orbit around Earth created by humans that no The Kessler Syndrome is a scenario proposed by NASA consultant Donald J 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. United States Strategic Command (USSTRATCOM is one of the ten Unified Combatant Commands of the U [4]
See also
- List of orbits
- Escape Velocity
- Medium Earth Orbit (MEO)
- Highly Elliptical Orbit (HEO)
- specific orbital energy examples
- International Space Station
- Atmospheric reentry
- Satellite phone
References
- ^ IADC Space Debris Mitigation Guidelines. The following is a list of types of orbits Centric classifications Galactocentric orbit: An orbit about the center of a Galaxy Medium Earth Orbit (MEO, sometimes called Intermediate Circular Orbit (ICO is the region of space around the Earth above low Earth orbit ( and below Geostationary orbit 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 \epsilon\\! (or vis-viva energy) of an Orbiting body traveling through Space A satellite telephone, satellite phone, or satphone is a type of Mobile phone that connects to orbiting Satellites instead of terrestrial Inter-Agency Space Debris Coordination Committee (15 Oct 2002). The Inter-Agency Space Debris Coordination Committee is an inter-governmental agency whose aim is to co-ordinate efforts to deal with debris in orbit around the Earth
- ^ NASA Safety Standard 1740.14, Guidelines and Assessment Procedures for Limiting Orbital Debris. Office of Safety and Mission Assurance (1 Aug 1995).
- ^ Observing the International Space Station. Canadian Space Agency. Retrieved on 2008-01-17. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 38 BC - Octavian marries Livia Drusilla. 1287 - King Alfonso III of Aragon invades Minorca
- ^ USSTRATCOM Space Control Fact Sheet
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic