Fr.: orbite d'aberration
The apparent path described by a star on the → celestial sphere due → annual aberration. A star at the → ecliptic pole is seen to move around a circle of angular radius about 20".50, once a year. A star on the → ecliptic oscillates to and fro along a line of angular half-length 20".50. At an intermediate → celestial latitude, β, the aberration orbit is an ellipse, with semi-major axis 20".50 and semi-minor axis (20".50) sin β.
Fr.: orbite liée
The orbit described by an object around a central gravitational force in a system whose total energy is negative. An elliptical orbit.
Of or relating to two or more celestial bodies that share, or almost share, the same orbit.
Fr.: mouvement co-orbital
The motion of two or more bodies around the Sun on different orbits when it takes them the same amount of time to complete one revolution. There are three possible types of co-orbital motions of a small body associated with a planet: → tadpole orbits, → horseshoe orbits, and → quasi-satellite orbits.
mâhvâre-ye ham-madâr, bandevâr-e ~
Fr.: satellite co-orbital
Any of satellites which either share the same orbit or which occupy immediately adjacent orbits that change periodically as the satellites approach one another (Ellis et al., 2007, Planetary Ring Systems, Springer).
Fr.: co-orbitage; c-orbitant, co-orbiteur
The action or quality of a → co-orbiting asteroid.
Fr.: astéroïde co-orbiteur
An asteroid having a → co-orbital motion.
Fr.: orbite de comète
The → path followed by a → comet in the → solar system around the → Sun. Most cometary orbits appear to be → elliptical, or in some cases → parabolic. The orbits of → short-period comets are elliptical, carrying them out to a region lying from → Jupiter to beyond the orbit of → Neptune. Those of → long-period comets are very elliptical. The orbits may be strongly influenced if they pass near the Jovian planets, particularly Jupiter itself. The cometary orbits are also influenced to some degree by gases shooting out of comets, so their orbits are primarily but not completely determined by gravity. Newton (1644-1727) was the first to compute a cometary orbit. He found that the comet of 1680 was following a parabolic orbit around the Sun. Edmond Halley (1656-1742), following the methods of Newton, computed the → orbital elements of 24 comets. He realized that the comets of 1531, 1607 and 1682 had very similar elements and postulated that they were in fact the same object, orbiting an elongated ellipse. He predicted the next return to occur in 1758 or early 1759. The return of what is now called Halley's comet was observed after his death, This first observation of a "predicted" comet is manifestly one of the major successes of → celestial mechanics.
Fr.: orbites commensurables
Of two bodies orbiting around a common barycenter, when the orbital period of one is an exact fraction, for example one-half or two-thirds, of the other.
To cause a spacecraft to leave its operational orbit to enter a descent phase or to change course.
Of a spacecraft, the act or process of departing from an operational orbit. → de-orbit.
Noun form of → de-orbit.
elements of the orbit
bonpârhâ-ye madâr, onsorhâ-ye ~ (#)
Fr.: éléments orbitaux
madâr-e derâzidé, ~ kašidé
Fr.: orbite allongée
Fr.: orbite géostationnaire
A satellite orbit in the plane of the Earth's equator and 35,880 km above it, at which distance the satellite's period of rotation matches the Earth's and the satellite always remains fixed in the same spot over the Earth.
Fr.: orbite géosynchrone
A circular orbit around the Earth identical to a geostationary orbit except that the satellite's orbit does not necessarily lie in the Earth's equatorial plane.
Fr.: orbite en fer à cheval
A periodic orbit which passes around the → Lagrangian points L4, L3, and L5, but neither of the two primaries. This orbit is shaped like a horseshoe when viewed in a reference frame rotating with the primaries. Such orbits occur in the solar system, for example in the case of the satellites → Janus and → Epimetheus, which share the same orbit around → Saturn. The smaller Epimetheus encompasses both the L4 and L5 points associated with the larger Janus and performs a horseshoe orbit relative to Saturn and Janus. The satellites experience a close approach every 4 years during which their orbits are exchanged. → tadpole orbit.
madâr-e hozluli (#)
Fr.: orbite hyperbolique
An orbit that is an open curve whose ends get wider apart at any rate between that of an ellipse and a straight line. Some comets' orbits become hyperbolic through the gravitational influence of a planet the comet passes near.
madâr-e Kepleri (#)
Fr.: orbit keplérienne
The orbit of a spherical object of a finite mass around another spherical object, also of finite mass, governed by their mutual → gravitational forces only.
Fr.: orbite de Lissajous
A quasi-periodic path resembling a → Lissajous figure around the L1 or L2 → Lagrangian points of a two-body system. Lissajous orbits, resulting from a combination of planar and vertical components, are used by certain space telescopes (such as → WMAP, → Planck Satellite, and → Herschel Satellite) that are required to be in a stable position relative to the Earth and Sun while making long-term observations.
lunar orbit node
gereh-e madâri-ye mâh
Fr.: nœud de l'orbite lunaire
Same as → lunar node.