Low Earth orbit

Low EarthLEOlow-Earth orbitorbitEarth orbitLow Earth Orbit (LEO)orbitallower orbitlowlow orbit
A low Earth orbit (LEO) is an Earth-centered orbit with an altitude of or less (approximately one-third of the radius of Earth), or with at least 11.25 periods per day (an orbital period of 128 minutes or less) and an eccentricity less than 0.25.wikipedia
2,335 Related Articles

Geocentric orbit

GeocentricEarth orbitEarth-orbit
A low Earth orbit (LEO) is an Earth-centered orbit with an altitude of or less (approximately one-third of the radius of Earth), or with at least 11.25 periods per day (an orbital period of 128 minutes or less) and an eccentricity less than 0.25.
For a low Earth orbit, this velocity is about 7800 m/s; by contrast, the fastest manned airplane speed ever achieved (excluding speeds achieved by deorbiting spacecraft) was 2200 m/s in 1967 by the North American X-15.

International Space Station

ISSInternational Space Station (ISS)Space Station
The International Space Station conducts operations in LEO.
The International Space Station (ISS) is a space station (habitable artificial satellite) in low Earth orbit.

Satellite

satellitesartificial satelliteartificial satellites
All crewed space stations to date, as well as the majority of satellites, have been in LEO.
Approximately 63% of operational satellites are in low-Earth orbit, 6% are in medium-Earth orbit (at 20,000 km), 29% are in geostationary orbit (at 36,000 km) and the remaining 2% are in elliptic orbit.

Space station

space stationsorbital stationstation
All crewed space stations to date, as well as the majority of satellites, have been in LEO.
, one fully operational and permanently inhabited space station is in low Earth orbit: the International Space Station (ISS), which is used to study the effects of long-term space flight on the human body as well as to provide a location to conduct a greater number and length of scientific studies than is possible on other space vehicles.

Apollo 8

8Apollo 8 missionApollo8
Apollo 8 was the first mission to carry humans beyond LEO on December 21–27, 1968.
Apollo 8 was the first crewed spacecraft to leave low Earth orbit and the first to reach the Moon, orbit it, and return.

Human spaceflight

space travelmannedmanned spaceflight
The altitude record for human spaceflights in LEO was Gemini 11 with an apogee of. The Apollo program continued during the four-year period spanning 1968 through 1972 with 24 astronauts who flew lunar flights but since then there have been no human spaceflights beyond LEO.
These rockets were large enough to be adapted to carry the first artificial satellites into low Earth orbit.

List of Apollo astronauts

Apollo Astronauts24 people to have flown to the MoonApollo astronaut
The Apollo program continued during the four-year period spanning 1968 through 1972 with 24 astronauts who flew lunar flights but since then there have been no human spaceflights beyond LEO.
Apart from these 24 men, no human being has gone beyond low Earth orbit.

Apollo program

ApolloProject ApolloApollo space program
The Apollo program continued during the four-year period spanning 1968 through 1972 with 24 astronauts who flew lunar flights but since then there have been no human spaceflights beyond LEO.
It stands alone in sending crewed missions beyond low Earth orbit.

Outer space

spaceinterstellar spaceintergalactic medium
Most of the manmade objects in outer space are in LEO.
For a low Earth orbit, this velocity is about 7800 m/s; by contrast, the fastest manned airplane speed ever achieved (excluding speeds achieved by deorbiting spacecraft) was 2200 m/s in 1967 by the North American X-15.

Atmospheric entry

atmospheric reentryreentryre-entry
Sub-orbital objects can also reach the LEO region but are not in an LEO orbit because they re-enter the atmosphere.
The five species model is only usable for entry from low Earth orbit where entry velocity is approximately.

Medium Earth orbit

Medium EarthMEOintermediate circular orbit
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 Earth above low Earth orbit (altitude of 2000 km above sea level) and below geosynchronous orbit (altitude of 35786 km above sea level).

Gravity drag

gravity lossesgravitationalgravity losses.
Atmospheric and gravity drag associated with launch typically adds to the launch vehicle delta-v required to reach normal LEO orbital velocity of around.
For example, to reach a speed of 7.8 km/s in low Earth orbit requires a delta-v of between 9 and 10 km/s.

Satellite constellation

constellationsatellite constellationsconstellations
Satellites in LEO have a small momentary field of view, only able to observe and communicate with a fraction of the Earth at a time, meaning a network (or "constellation") of satellites is required to in order to provide continuous coverage.
Low Earth orbiting satellites (LEOs) are often deployed in satellite constellations, because the coverage area provided by a single LEO satellite only covers a small area that moves as the satellite travels at the high angular velocity needed to maintain its orbit.

Communications satellite

satellite communicationssatellitecommunication satellite
Some communication satellites use much higher geostationary orbits, and move at the same angular velocity as the Earth as to appear stationary above one location on the planet.
A low Earth orbit (LEO) typically is a circular orbit about 160 to 2,000 km above the earth's surface and, correspondingly, a period (time to revolve around the earth) of about 90 minutes.

Orbital decay

decayeddecayingdecay
Satellites in lower regions of LEO also suffer from fast orbital decay, requiring either periodic reboosting to maintain a stable orbit, or launching replacement satellites when old ones re-enter.
For bodies in low Earth orbit, the most significant effect is atmospheric drag.

Hubble Space Telescope

HubbleHSTHubble Telescope
The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation.

Iridium Communications

IridiumIridium Satellite LLCIridium Communications Inc.
Since it requires less energy to place a satellite into a LEO, and a satellite there needs less powerful amplifiers for successful transmission, LEO is used for many communication applications, such as the Iridium phone system.
The satellites are in six polar low Earth orbital planes at a height of approximately 485 mi.

Latency (engineering)

latencylow latencylow-latency
It provides high bandwidth and low communication latency.
Low Earth orbit is sometimes used to cut this delay, at the expense of more complicated satellite tracking on the ground and requiring more satellites in the satellite constellation to ensure continuous coverage.

Space debris

orbital debrisspace junkdebris
The LEO environment is becoming congested with space debris because of the frequency of object launches.
A large-enough collision (e.g. between a space station and a defunct satellite) could make low Earth orbit impassable.

Gravity Field and Steady-State Ocean Circulation Explorer

GOCEGoce satellite
The satellite's unique arrow shape and fins helped keep GOCE stable as it flew through the thermosphere at a comparatively low altitude of 255 km.

Kessler syndrome

causing the debris to destroy all the satellites at that altitudechain reactioncollisional cascade
Collisions can produce even more space debris in the process, creating a domino effect, something known as Kessler Syndrome.
The Kessler syndrome (also called the Kessler effect, collisional cascading, or ablation cascade), proposed by the NASA scientist Donald J. Kessler in 1978, is a scenario in which the density of objects in low Earth orbit (LEO) is high enough that collisions between objects could cause a cascade in which each collision generates space debris that increases the likelihood of further collisions.

Van Allen radiation belt

Van Allen beltsradiation beltVan Allen belt
Objects in LEO orbit Earth between the denser part of the atmosphere and below the inner Van Allen radiation belt.
Spacecraft travelling beyond low Earth orbit enter the zone of radiation of the Van Allen belts.

Heavy-lift launch vehicle

heavy lift launch vehicleheavy-liftheavy lift
20000 to 50000 kg to low Earth orbit (LEO).

Earth observation satellite

Earth observationenvironmental satelliteEarth observation satellites
The Earth observation satellites of UAE, DubaiSat-1 & DubaiSat-2 are also placed in Low Earth Orbits (LEO) orbits and providing satellite imagery of various parts of the Earth.

Comparison of orbital launch systems

Comparison of heavy lift launch systemsthe most usedComparison of small lift launch systems