# List of orbits

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:

## 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.

## Synchronicity classifications

• 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

• 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.[8] 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.[8]

## Pseudo-orbit classifications

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.

## References

1. ^ "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.
2. ^ 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.
3. ^ Vallado, David A. (2007). Fundamentals of Astrodynamics and Applications. Hawthorne, CA: Microcosm Press. p. 31.
4. ^ Hadhazy, Adam (22 December 2014). "A New Way to Reach Mars Safely, Anytime and on the Cheap". Scientific American. Retrieved 25 December 2014.
5. ^ Whipple, P. H . (1970-02-17). "Some Characteristics of Coelliptic Orbits – Case 610". Bellcom Inc. Washington: NASA. Archived from the original (PDF) on 2012-05-24. Retrieved 2012-05-23.
6. ^ "U.S. Government Orbital Debris Mitigation Standard Practices" (PDF). United States Federal Government. Retrieved 2013-11-28.
7. ^ 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.
8. ^ a b Merritt, David (2013). Dynamics and Evolution of Galactic Nuclei. Princeton: Princeton University Press. ISBN 9780691121017.
9. ^ Kirstyn Johnson (18 December 2014). "Understanding NASA's Asteroid Redirect Mission". Retrieved 14 June 2015.
10. ^ "Asteroid Redirect Mission Reference Concept" (PDF). www.nasa.gov. NASA. Retrieved 14 June 2015.