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In astronomy, and in particular in astrodynamics, the osculating orbit of an object in space is the gravitational Keplerian orbit about a central body which best approximates the (more complex) motion of the object at a given instant in time.

An osculating orbit and the object's position upon it are fully described by the six standard Keplerian orbital elements.

An orbit is usually said to be osculating to point out that its details change over a relevant time. The most common situations in which osculating orbits are specified are:

• The orbit of spacecraft, particularly those powered by ion engines which act to slowly change the orbit's parameters.
• When considering perturbations of the Keplerian orbit by bodies other than the central body.
• To contrast the slowly changing osculating orbital elements to the proper orbital elements, which remain practically constant over timescales of millions of years.

[edit] See also

• Osculation
• Osculating circle
• proper orbital elements

[edit] External links

• Diagram of a sequence of osculating orbits for the escape from Earth orbit by the ion-driven SMART-1 spacecraft: http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=35722
• A sequence of osculating orbits for the approach to the Moon by the SMART-1 spacecraft: http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=36359