List of orbits
This is a list of types of gravitational orbit classified by various characteristics.
Common abbreviations
List of abbreviations of common Earth orbits
Orbit | Name |
---|---|
GEO | Geostationary orbit |
LEO | Low Earth orbit |
MEO | Medium Earth orbit |
SSO | Sun-synchronous orbit |
List of abbreviations of other orbits
Orbit | Name |
---|---|
GSO | Geosynchronous orbit |
GTO | Geostationary transfer orbit |
HCO | Heliocentric orbit |
HEO | Highly elliptical orbit |
NRHO | Near-rectilinear halo orbit |
VLEO | Very Low Earth Orbit |
Classifications
The following is a list of types of orbits:
Centric classifications
- Galactocentric orbit:[2] An orbit about the center of a galaxy. The Sun follows this type of orbit about the Galactic Center of the Milky Way.
- Moons by contrast are not in a heliocentric orbitbut rather orbit their parent object.
- artificial satellites.
- .
- artificial satellites.
For orbits centered about planets other than Earth and Mars and for the dwarf planet Pluto, the orbit names incorporating Greek terminology is less commonly used
- Mercury orbit (.
- Venus orbit (Cythera): An orbit around the planet Venus.
- Jupiter orbit (.
- Saturn orbit (.
- Uranus orbit (.
- Neptune orbit (.
- Pluto orbit (.
Altitude classifications for geocentric orbits
- perigee that intersects with the defined atmosphere.[4]
- Very low Earth orbit (VLEO) is defined as altitudes between approximately 100 - 450 km above Earth’s surface.[5][6]
- Low Earth orbit (LEO): geocentric orbits with altitudes below 2,000 km (1,200 mi).[7]
- semi-major axis of 42,164 km (26,199 mi).[10]This works out to an altitude of 35,786 km (22,236 mi). Both complete one full orbit of Earth per sidereal day (relative to the stars, not the Sun).
- High Earth orbit: geocentric orbits above the altitude of geosynchronous orbit (35,786 km or 22,236 mi).[8]
For Earth orbiting satellites below the height of about 800 km, the atmospheric drag is the major orbit perturbing force out of all non-gravitational forces.[11] Above 800 km, solar radiation pressure causes the largest orbital perturbations.[12] However, the atmospheric drag strongly depends on the density of the upper atmosphere, which is related to the solar activity, therefore the height at which the impact of the atmospheric drag is similar to solar radiation pressure varies depending on the phase of the solar cycle.
Inclination classifications
- equatorial planeis not 0.
- inclination of (or very close to) either 90 degreesor −90 degrees.
- Polar Sun-synchronous orbit (SSO): A nearly polar orbit that passes the equator at the same local solar time on every pass. Useful for image-taking satellites because shadows will be the same on every pass.
- plane of reference.
- equatorial planeis nearly zero. This orbit allows for rapid revisit times (for a single orbiting spacecraft) of near equatorial ground sites.
Directional classifications
- inclinationof a Prograde orbit is specified as an angle less than 90°.
- .
Eccentricity classifications
There are two types of orbits: closed (periodic) orbits, and open (escape) orbits. Circular and elliptical orbits are closed. Parabolic and hyperbolic orbits are open. Radial orbits can be either open or closed.
- Circular orbit: An orbit that has an eccentricity of 0 and whose path traces a circle.
- Elliptic orbit: An orbit with an eccentricity greater than 0 and less than 1 whose orbit traces the path of an ellipse.
- apogee at the altitude of a geostationary orbit.
- 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.
- Ballistic capture orbit: a lower-energy orbit than a Hohmann transfer orbit, a spacecraft moving at a lower orbital velocity than the target celestial body is inserted into a similar orbit, allowing the planet or moon to move toward it and gravitationally snag it into orbit around the celestial body.[13]
- Coelliptic orbit: A relative reference for two spacecraft—or more generally, coplanar and confocal. A property of coelliptic orbits is that the difference in magnitude between aligned radius vectors is nearly the same, regardless of where within the orbits they are positioned. For this and other reasons, coelliptic orbits are useful in [spacecraft] rendezvous".[14]
- 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 gravitational pull of the planet. If the speed of a parabolic orbit is increased it will become a hyperbolic orbit.
- parabolic orbit where the object has escape velocity and is moving away from the planet.
- parabolic orbit where the object has escape velocity and is moving toward the planet.
- infinitelyuntil it is acted upon by another body with sufficient gravitational force.
- Radial orbit: An orbit with zero angular momentumand eccentricity equal to 1. The two objects move directly towards or away from each other in a straight-line.
- Radial elliptic orbit: A closed elliptic orbit where the object is moving at less than the escape velocity. This is an elliptic orbit with semi-minor axis = 0 and eccentricity = 1. Although the eccentricity is 1, this is not a parabolic orbit.
- parabolic orbit where the object is moving at the escape velocity.
- hyperbolic orbit where the object is moving at greater than the escape velocity. This is a hyperbolic orbit with semi-minor axis = 0 and eccentricity = 1. Although the eccentricity is 1, this is not a parabolic orbit.
Synchronicity classifications
- rotational periodof the body being orbited and in the same direction of rotation as that body. This means the track of the satellite, as seen from the central body, will repeat exactly after a fixed number of orbits. In practice, only 1:1 ratio (geosynchronous) and 1:2 ratios (semi-synchronous) are common.
- Clarke orbit after the writer Arthur C. Clarke.[8]
- inclination of zero. To an observer on the ground this satellite appears as a fixed point in the sky. "All geostationary orbits must be geosynchronous, but not all geosynchronous orbits are geostationary."[8]
- sidereal day, 24.6229 hours.
- km (10,557 miles) above the surface of Mars. To an observer on Mars this satellite would appear as a fixed point in the sky.
- Subsynchronous orbit: A drift orbit close below GSO/GEO.
- rotational period of the body being orbited and in the same direction of rotation as that body. For Earth this means a period of just under 12 hours at an altitude of approximately 20,200 km (12,544.2 miles) if the orbit is circular.[16]
- Molniya orbit: A semi-synchronous variation of a Tundra orbit. For Earth this means an orbital period of just under 12 hours. Such a satellite spends most of its time over two designated areas of the planet. An inclination of 63.4° is normally used to keep the perigee shift small.[15]
- barycenterof the orbit.
Orbits in galaxies or galaxy models
- Box orbit: An orbit in a triaxial elliptical galaxy that fills in a roughly box-shaped region.
- Pyramid orbit: An orbit near a massive black hole at the center of a triaxial galaxy.[17] The orbit can be described as a Keplerian ellipse that precesses about the black hole in two orthogonal directions, due to torques from the triaxial galaxy.[18] The eccentricity of the ellipse reaches unity at the four corners of the pyramid, allowing the star on the orbit to come very close to the black hole.
- Tube orbit: An orbit near a massive black hole at the center of an axisymmetric galaxy. Similar to a pyramid orbit, except that one component of the orbital angular momentum is conserved; as a result, the eccentricity never reaches unity.[18]
Special classifications
- spy, and weather satellites.
- Frozen orbit: An orbit in which natural drifting due to the central body's shape has been minimized by careful selection of the orbital parameters.
- elliptical-inclined orbit.
- Beyond-low Earth orbit (BLEO) and beyond Earth orbit (BEO) are a broad class of orbits that are orbital insertions, respectively.
- cislunar space, as a selenocentric orbit that will serve as a staging area for future missions. [19][20] Planned orbit for the NASA Lunar Gateway in circa 2024, as a highly-elliptical seven-day near-rectilinear halo orbit around the Moon, which would bring the small space station within 3,000 kilometers (1,900 mi) of the lunar north pole at closest approach and as far away as 70,000 kilometers (43,000 mi) over the lunar south pole.[21][22][23]
- retrograde orbit (usually referring to Lunar Distant Retrograde Orbit). Stability means that satellites in DRO do not need to use station keeping propellant to stay in orbit. The lunar DRO is a high lunar orbit with a radius of approximately 61,500 km.[24] This was proposed[by whom?] in 2017 as a possible orbit for the Lunar Gateway space station, outside Earth-Moon L1 and L2.[20]
- Decaying orbit: A decaying orbit is an orbit at a low altitude that decreases over time due atmospheric resistance. Used to dispose of dying artificial satellites or to aerobrakean interplanetary spacecraft.
- Earth-trailing orbit, a heliocentric orbit that is placed such that the satellite will initially follow Earth but at a somewhat slower orbital angular speed, such that it moves further behind year by year. This orbit was used on the Spitzer Space Telescope in order to drastically reduce the heat load from the warm Earth from a more typical geocentric orbit used for space telescopes.[25]
- Parking orbit, a temporary orbit.
- Transfer orbit, an orbit used during an orbital maneuver from one orbit to another.
- Lunar transfer orbit (LTO)[clarification needed] accomplished with trans-lunar injection(TLI)
- Mars transfer orbit(MTO) also known as trans-Mars injection (TMI) orbit
- Repeat orbit: An orbit where the ground track of the satellite repeats after a period of time.
- Gangale orbit: a solar orbit near Mars whose period is one Martian year, but whose eccentricity and inclination both differ from that of Mars such that a relay satellite in a Gangale orbit is visible from Earth even during solar conjunction.[28]
Pseudo-orbit classifications
- Horseshoe orbit: An orbit that appears to a ground observer to be orbiting a certain planet but is actually in co-orbit with the planet. See asteroids 3753 Cruithne and 2002 AA29.
- Lagrangian point. Lagrange points are shown in the adjacent diagram, and orbits near these points allow a spacecraft to stay in constant relative position with very little use of fuel. Orbits around the L1 point are used by spacecraft that want a constant view of the Sun, such as the Solar and Heliospheric Observatory. Orbits around L2 are used by missions that always want both Earth and the Sun behind them. This enables a single shield to block radiation from both Earth and the Sun, allowing passive cooling of sensitive instruments. Examples include the Wilkinson Microwave Anisotropy Probe and the James Webb Space Telescope. L1, L2, and L3 are unstable orbits[6], meaning that small perturbations will cause the orbiting craft to drift out of the orbit without periodic corrections.
- P/2 orbit, a highly-stable 2:1 lunar resonant orbit, that was first used with the spacecraft TESS (Transiting Exoplanet Survey Satellite) in 2018.[29][30]
See also
Notes
- ^ Orbital periods and speeds are calculated using the relations 4π2R3 = T2GM and V2R = GM, where R = radius of orbit in metres, T = orbital period in seconds, V = orbital speed in m/s, G = gravitational constant ≈ 6.673×10−11 Nm2/kg2, M = mass of Earth ≈ 5.98×1024 kg.
- ^ Approximately 8.6 times when the Moon is nearest (363,104 km ÷ 42,164 km) to 9.6 times when the Moon is farthest (405,696 km ÷ 42,164 km).
References
- ^ a b "Types of Orbits". Space Foundation.
- ^ "Definition of GALACTOCENTRIC". www.merriam-webster.com. Retrieved 3 June 2020.
- ^ ISBN 007042313X.
- ^ McDowell, Jonathan (24 May 1998). "Jonathan's Space Report".
Transatmospheric orbit (TAO): orbital flight with perigee less than 80 km but more than zero. Potentially used by aerobraking missions and transatmospheric vehicles, also in some temporary phases of orbital flight (e.g. STS pre OMS-2, some failures when no apogee restart)
- ^ "Stingray VLEO Constellation".
- ^ "Attitude control for satellites flying in VLEO using aerodynamic surfaces".
- ^ "NASA Safety Standard 1740.14, Guidelines and Assessment Procedures for Limiting Orbital Debris" (PDF). Office of Safety and Mission Assurance. 1 August 1995. p. A-2. Archived from the original (PDF) on 15 February 2013.
Low Earth orbit (LEO) – The region of space below the altitude of 2000 km.
, pages 37–38 (6–1,6–2); figure 6-1. - ^ a b c d "Orbit: Definition". Ancillary Description Writer's Guide, 2013. National Aeronautics and Space Administration (NASA) Global Change Master Directory. Archived from the original on 11 May 2013. Retrieved 29 April 2013.
- ^ "Types of orbits".
- ^ Vallado, David A. (2007). Fundamentals of Astrodynamics and Applications. Hawthorne, CA: Microcosm Press. p. 31.
- .
- .
- ^ Hadhazy, Adam (22 December 2014). "A New Way to Reach Mars Safely, Anytime and on the Cheap". Scientific American. Retrieved 25 December 2014.
- ^ Whipple, P. H . (17 February 1970). "Some Characteristics of Coelliptic Orbits – Case 610" (PDF). Bellcom Inc. Washington: NASA. Archived from the original (PDF) on 21 May 2010. Retrieved 23 May 2012.
- ^ a b This answer explains why such inclination keeps apsidial drift small: https://space.stackexchange.com/a/24256/6834
- ^ "Catalog of Earth Satellite Orbits". earthobservatory.nasa.gov. NASA. 4 September 2009. Retrieved 4 May 2022.
- ^ Merritt and Vasilev, ORBITS AROUND BLACK HOLES IN TRIAXIAL NUCLEI", The Astrophysical Journal 726(2), 61 (2011).
- ^ ISBN 9780691121017.
- ^ Leonard David (15 March 2018). "NASA Shapes Science Plan for Deep-Space Outpost Near the Moon". Space.com.
- ^ a b How a New Orbital Moon Station Could Take Us to Mars and Beyond Oct 2017 video with refs
- ^ Angelic halo orbit chosen for humankind's first lunar outpost. European Space Agency, Published by PhysOrg. 19 July 2019.
- ^ Halo orbit selected for Gateway space station. David Szondy, New Atlas. 18 July 2019.
- ^ Foust, Jeff (16 September 2019). "NASA cubesat to test lunar Gateway orbit". SpaceNews. Retrieved 15 June 2020.
- ^ "Asteroid Redirect Mission Reference Concept" (PDF). www.nasa.gov. NASA. Retrieved 14 June 2015.
- ^ "About Spitzer: Fast Facts". Caltech. 2008. Archived from the original on 2 February 2007. Retrieved 22 April 2007.
- ^ "U.S. Government Orbital Debris Mitigation Standard Practices" (PDF). United States Federal Government. Retrieved 28 November 2013.
- ^
Luu, Kim; Sabol, Chris (October 1998). "Effects of perturbations on space debris in supersynchronous storage orbits" (PDF). Air Force Research Laboratory Technical Reports (AFRL-VS-PS-TR-1998-1093). Bibcode:1998PhDT.......274L. Archived(PDF) from the original on 3 December 2013. Retrieved 28 November 2013.
- ^ Byford, Dorothy (September 2008). "Optimal Location of Relay Satellites for Continuous Communication with Mars".
- ^ Keesey, Lori (31 July 2013). "New Explorer Mission Chooses the 'Just-Right' Orbit". NASA. Retrieved 5 April 2018.
- ^ Overbye, Dennis (26 March 2018). "Meet Tess, Seeker of Alien Worlds". The New York Times. Retrieved 5 April 2018.