9 articles for "Orbital"

**Orbital Eccentricity**[Astro*Index]

Literally, an orbit's deviation from a perfect circle. It is usually denoted by the letter e. A conic is defined as any curve which is the locus of a point which moves in such manner that the ratio of its distance from a fixed point (called the focus) to its distance from a fixed line (called the directrix) is constant. This ratio is called the* eccentricity.*

See also: ♦ Conic Section ♦ Orbit ♦ Eccentricity

**Orbital Eccentricity**[Munkasey M.]

That measure which shows the amount of devia-tion that a Body's orbit has from being a circular orbit.

See also: ♦ Conic Section ♦ Orbit ♦ Eccentricity

**Orbital Elements**[Astro*Index]

The solution of Newton's equations of motion for a planet orbiting the Sun requires the determination of six constants of integration at some specified *epoch* (time). These six constants are called the orbital elements. There are many ways to express these elements. For artificial satellite orbits, these elements are the three position components and the three velocity components at the epoch. The classic elements are the *semi- major axis*, the eccentricity, the *mean anomaly*, the *argument of perihelion*, the *orbital inclination* and the longitude of the ascending node at the epoch. See Figure O1. Sometimes the longitude of the perihelion (the longitude of the ascending node plus the argument of perihelion) is specified instead of the argument of perihelion.

See also: ♦ Ascending Node ♦ Orbital Eccentricity ♦ Epoch ♦ Semi-Major Axis ♦ Mean Anomaly ♦ Argument of Perihelion

**Orbital Elements**[Munkasey M.]

The seven terms which are used in Celestial Mechanics to define a Body's motion in space. These are: Semi-Major Axis; Eccentricity; Inclination; Longitude of the Ascending Node; Argument of the Perihelion; Sidereal Period of the Body; and Epoch.

See also: ♦ Ascending Node ♦ Orbital Eccentricity ♦ Epoch ♦ Semi-Major Axis ♦ Mean Anomaly ♦ Argument of Perihelion

**Orbital Period**[Astro*Index]

Time required for a body to complete one *orbit.*

See also: ♦ Sidereal Period ♦ Anomalistic Period ♦ Synodic Period ♦ Orbit

**Orbital Period**[Munkasey M.]

Used in the same sense as: "Sidereal Period".

See also: ♦ Sidereal Period ♦ Anomalistic Period ♦ Synodic Period ♦ Orbit

**Orbital Revolution**[DeVore]

The annual motion of the Earth in an elliptical orbit round the Sun. Applicable also to the motion of any celestial body which pursues an orbit around any other body.

See also: ♦ Orbit

**Orbital Scheme**[Prima]

Shows the orbital positions of the planets with respect to the Sun. For easy viewing, the diagram is divided into two parts: the orbits of Mercury through Jupiter, and the orbits of Jupiter through Pluto. The longitudinal positions of the planets are listed below the diagram, along with their degrees of north or south (-) latitude. The diagram can be used to determine, for example, whether conjunctions of Mercury and Venus with the Sun are "interior" or "superior," or it can be used to see heliocentric alignments, which would not otherwise be apparent from the geocentric chart.

See also: ♦ Sidereal Period ♦ Anomalistic Period ♦ Synodic Period ♦ Orbit

**Orbital Velocity**[Astro*Index]

**1.** Velocity of an orbiting body at any given point in its orbit.

**2.** The velocity required by an object to enter into orbit about another body.

Orbital Velocity may be computed from the formula: v = sqrt(gR2(2/r - 1/a)) where: R = radius of orbiting body r = distance from centre of mass a = semi-major axis of orbiting body g = acceleration of gravity For a circular orbit, r=a, and: v = sqrt((gR2/r)) For an elliptical orbit, the period, P, is given by: P = 2ãa3/2/sqrt(gR2)

See also: ♦ Escape Velocity

Astro*Index Copyright © 1997 Michael Erlewine

[ TOP ]