# eccentricity

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**Orbital elements**— are the parameters required to uniquely identify a specific orbit. In celestial mechanics these elements are generally considered in classical two body systems, where a Kepler orbit is used (derived from Newton s laws of motion and Newton s law… …62

**Astronomy on Mars**— Mosaic of two different Mars Global Surveyor Mars Orbiter Camera (MOC) exposures of Earth, the Moon, and Jupiter from 2003 …63

**Newton's theorem of revolving orbits**— Figure 1: An attractive force F(r) causes the blue planet to move on the cyan circle. The green planet moves three times faster and thus requires a stronger centripetal force, which is supplied by adding an attractive inverse cube force. The …64

**Meridian arc**— In geodesy, a meridian arc measurement is a highly accurate determination of the distance between two points with the same longitude. Two or more such determinations at different locations then specify the shape of the reference ellipsoid which… …65

**Comet**— This article is about the astronomical object. For other uses, see Comet (disambiguation). Comet Hale– …66

**Satellite**— This article is about artificial satellites. For natural satellites, also known as moons, see Natural satellite. For other uses, see Satellite (disambiguation). An animation depicting the orbits of GPS satellites in medium Earth orbit …67

**Orbital speed**— Not to be confused with Escape Velocity. The orbital speed of a body, generally a planet, a natural satellite, an artificial satellite, or a multiple star, is the speed at which it orbits around the barycenter of a system, usually around a more… …68

**Equation of time**— The equation of time is the difference over the course of a year between time as read from a sundial and time as read from a clock, measured in an ideal situation (ie. in a location at the centre of a time zone, and which does not use daylight… …69

**Semi-major axis**— The semi major axis of an ellipse The major axis of an ellipse is its longest diameter, a line that runs through the centre and both foci, its ends being at the widest points of the shape. The semi major axis is one half of the major axis, and… …70

**Geodetic system**— For other uses, see Geodetic. Geodesy Fundamentals …