List of orbits

From Wikipedia, the free encyclopedia
  (Redirected from Coelliptic orbit)
Jump to: navigation, search
Various Earth orbits to scale; innermost, the red dotted line represents the orbit of the International Space Station (ISS); cyan represents low Earth orbit, yellow represents medium Earth orbit, and the black dashed line represents geosynchronous orbit. The green dash-dot line represents the orbit of Global Positioning System (GPS) satellites.

The following is a list of types of orbits:

Centric classifications[edit]

Altitude classifications for geocentric orbits[edit]

Inclination classifications[edit]

Eccentricity classifications[edit]

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.

Synchronicity classifications[edit]

  • Synchronous orbit: An orbit whose period is a rational multiple of the average rotational period of 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.
Geostationary orbit as seen from the north celestial pole. To an observer on the rotating Earth, the red and yellow satellites appear stationary in the sky above Singapore and Africa respectively.

Orbits in galaxies or galaxy models[edit]

  • 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. 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.[9] 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.[9]

Special classifications[edit]

Pseudo-orbit classifications[edit]

A diagram showing the five Lagrangian points in a two-body system with one body far more massive than the other (e.g. the Sun and the Earth). In such a system, L3L5 are situated slightly outside of the secondary's orbit despite their appearance in this small scale diagram.
  • 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.
  • Exo-orbit: A maneuver where a spacecraft achieves an orbit that is unstable due to atmospheric drag.
  • Lunar transfer orbit (LTO)
  • Prograde orbit: An orbit with an inclination of less than 90°. Or rather, an orbit that is in the same direction as the rotation of the primary.
  • Retrograde orbit: An orbit with an inclination of more than 90°. Or rather, an orbit counter to the direction of rotation of the planet. Apart from those in Sun-synchronous orbit, few satellites are launched into retrograde orbit because the quantity of fuel required to launch them is much greater than for a prograde orbit. This is because when the rocket starts out on the ground, it already has an eastward component of velocity equal to the rotational velocity of the planet at its launch latitude. A gravity assist around the moon can reduce the fuel premium. Retrograde orbits might be used as part of anti-satellite warfare.[citation needed]
  • Distant retrograde orbit (DRO): A stable circular 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.[10]
  • Mars transfer orbit (MTO)
  • Halo orbits and Lissajous orbits: These are orbits around a Lagrangian point. Lagrange points are shown in the diagram on the right, 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 upcoming 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.

See also[edit]

References[edit]

  1. ^ a b Parker, Sybil P. (2002). McGraw-Hill Dictionary of Scientific and Technical Terms Sixth Edition. McGraw-Hill. p. 1772. ISBN 007042313X. 
  2. ^ "NASA Safety Standard 1740.14, Guidelines and Assessment Procedures for Limiting Orbital Debris" (PDF). Office of Safety and Mission Assurance. 1 August 1995. , pages 37-38 (6-1,6-2); figure 6-1.
  3. ^ a b c d "Orbit: Definition". Ancillary Description Writer's Guide, 2013. National Aeronautics and Space Administration (NASA) Global Change Master Directory. Retrieved 2013-04-29. 
  4. ^ Vallado, David A. (2007). Fundamentals of Astrodynamics and Applications. Hawthorne, CA: Microcosm Press. p. 31. 
  5. ^ Hadhazy, Adam (22 December 2014). "A New Way to Reach Mars Safely, Anytime and on the Cheap". Scientific American. Retrieved 25 December 2014. 
  6. ^ Whipple, P. H . (1970-02-17). "Some Characteristics of Coelliptic Orbits – Case 610" (PDF). Bellcom Inc. Washington: NASA. Archived from the original (PDF) on 21 May 2010. Retrieved 2012-05-23. 
  7. ^ "U.S. Government Orbital Debris Mitigation Standard Practices" (PDF). United States Federal Government. Retrieved 2013-11-28. 
  8. ^ 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). Retrieved 2013-11-28. 
  9. ^ a b Merritt, David (2013). Dynamics and Evolution of Galactic Nuclei. Princeton: Princeton University Press. ISBN 9780691121017. 
  10. ^ "Asteroid Redirect Mission Reference Concept" (PDF). www.nasa.gov. NASA. Retrieved 14 June 2015.