Categories: Astronomy | Astrodynamics Illumination of Earth by Sun on the day of equinox The vernal equinox (or spring equinox) marks the beginning of astronomical spring. ... The ascending node is one of the orbital nodes, a point in the orbit of an object where it crosses the plane of the ecliptic from the south celestial hemisphere to the north celestial hemisphere in the direction of motion. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... In stellar dynamics a box orbit refers to a particular type of orbit which can be seen in triaxial systems, that is, systems which do not possess a symmetry around any of its axes. ... In astrodynamics or celestial mechanics a circular orbit is an elliptic orbit with the eccentricity equal to 0. ... Eclipitic orbit is an orbit with inclination to the plane of reference (i. ... Two bodies with similar mass orbiting around a common barycenter with elliptic orbits. ... Highly Elliptical Orbit (HEO) is an elliptic orbit characterized by a relatively low-altitude perigee and an extremely high-altitude apogee. ... A graveyard orbit is an orbit where spacecraft are intentionally placed at the end of their operational life. ... In astrodynamics or celestial mechanics a hyperbolic trajectory is an orbit with the eccentricity greater than 1. ... A geostationary orbit occurs when an object (satellite) is placed 37,000 km (22,300 miles) above the Earths equator with the characteristic that, from a fixed observation point on the Earths surface, it appears motionless. ... 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. ... In astrodynamics or celestial mechanics a parabolic trajectory is an orbit with the eccentricity equal to 1. ... A capture orbit is the high-energy parabolic orbit that allows the capture other than crashing directly to the central bodys surface (or atmospheric re_entry). ... An escape orbit (also known as C3 = 0 orbit) is the high-energy parabolic orbit around the central body. ... Semi-Synchronous Orbit (SSO): An orbit with approximately a 12-hour period. ... Unsurprisingly similar to synchronous orbit, this orbit is at a slightly different distance from the Earth, resulting in the satellite drifting slowly eastward. ... A synchronous orbit is an orbit in which an orbiting body (usually a satellite) has a period equal to the average rotational period of the body being orbited (usually a planet), and in the same direction of rotation as that body. ... Geocentric orbit refers to the orbit of any object orbiting the Earth, such as the Moon or artificial satellites. ... It has been suggested that this article or section be merged with geostationary orbit. ... A geostationary orbit (GEO) is a geosynchronous orbit directly above the Earths equator (0º latitude). ... By analogy with the geosynchronous orbit, a heliosynchronous orbit is a heliocentric orbit of radius 24. ... A low Earth orbit (LEO) is an orbit in which objects such as satellites are below intermediate circular orbit (ICO) and far below geostationary orbit, but typically around 350 - 1400 km above the Earths surface. ... Intermediate circular orbit (ICO), also called medium earth orbit (MEO), is used by satellites between the altitudes of low earth orbit (up to 1400 km) and geostationary orbit (ca. ... Molniya orbit is a class of a highly elliptic orbit with inclination of +/-63. ... A near equatorial orbit is an orbit that lies close to the equatorial plane of the object orbited. ... The Moon makes a complete orbit about the Earth approximately once every 27. ... A satellite in a polar orbit passes above or nearly above both poles of the planet (or other celestial body) on each revolution. ... A polar sun synchronous orbit is a nearly polar orbit. ... Tundra orbit is a class of a highly elliptic orbit with inclination of 63. ... Areosynchronous orbits are class of synchronous orbits for artificial satellites around the planet Mars. ... An areostationary orbit (abbreviated ASO) is a circular areo­synchronous orbit in the Martian equatorial plane 11,000 km above the surface, any point on which revolves about Mars in the same direction and with the same period as the Martian surface. ... In orbital mechanics, a Lissajous orbit is a quasi-periodic orbital trajectory an object can follow around a colinear libration point of a two-body system without requiring any propulsion. ... In astronomy, lunar orbit refers just to the orbit of the Moon around the Earth. ... A heliocentric orbit is an orbit around the sun. ... By analogy with the geosynchronous orbit, a heliosynchronous orbit is a heliocentric orbit of radius 24. ... The elements of an orbit are the parameters needed to specify that orbit uniquely, given a model of two ideal masses obeying the Newtonian laws of motion and the inverse-square law of gravitational attraction. ... Inclination in general is the angle between a reference plane and another plane or axis of direction. ... (This page refers to eccitricity in astrodynamics. ... The argument of periapsis (ω) is the orbital element describing the angle between an orbiting bodys ascending node (the point where the body crosses the plane of reference from South to North) and its periapsis (the point of closest approach to the central body), measured in the orbital plane and... The semi-major axis of an ellipse In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae. ... In the study of orbital dynamics the mean anomaly is a measure of time, specific to the orbiting body p, which is a multiple of 2π radians at and only at periapsis. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... In astronomy, the true anomaly (, also written ) is the angle between the direction z-s of periapsis and the current position p of an object on its orbit, measured at the focus s of the ellipse (the point around which the object orbits). ... In geometry, the semi-minor axis (also semiminor axis) applies to ellipses and hyperbolas. ... (This page refers to eccentricity in mathematics. ... The eccentric anomaly is the angle between the direction of periapsis and the current position of an object on its orbit, projected onto the ellipses circumscribing circle perpendicularly to the major axis, measured at the centre of the ellipse. ... In astrodynamics or celestial dynamics mean longitude of an orbiting body is . ... In astrodynamics true longitude is a . ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... An orbital maneuver is a change from one orbit to another, accomplished by applying thrust. ... In astronautics and aerospace engineering, the Bi-elliptic transfer is an orbital maneuver that moves a spacecraft from one orbit to another and may, in certain situations require less delta-v than a Hohmann transfer. ... A geostationary transfer orbit (GTO) is a Hohmann transfer orbit around the Earth between a low Earth orbit (LEO) and a geostationary orbit (GEO). ... It has been suggested that sling effect be merged into this article or section. ... In astronautics and aerospace engineering, the Hohmann transfer orbit is an orbital maneuver that, under standard assumption, moves a spacecraft from one circular orbit to another using two engine impulses. ... Orbital inclination change is a orbital maneuver aimed at changing inclination of orbiting bodys orbit. ... In astrodynamics orbital phasing is the adjustment of the time-position of spacecraft along its orbit, usually described as adjusting the orbiting spacecrafts true anomaly. ... A space rendezvous between two spacecraft, often between a spacecraft and a space station, is an orbital maneuver where the two arrive at the same orbit, make the orbital velocities the same, and bring them together (an approach maneuver, taxiing maneuver); it may or may not include docking. ... A diagram of Keplerian orbital elements. ... In astronomy, a celestial coordinate system is a coordinate system for mapping positions in the sky. ... Delta-v budget (or velocity change budget) is a term used in astrodynamics and aerospace industry for velocity change (or delta-v) requirements for the various propulsive tasks and orbital maneuvers over phases of the space mission. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... An ephemeris (plural: ephemerides) (from the Greek word ephemeros = daily) was, traditionally, a table providing the positions (given in a Cartesian coordinate system, or in right ascension and declination or, for astrologers, in longitude along the zodiacal ecliptic), of the Sun, the Moon, the planets, asteroids or comets in the... The equatorial coordinate system is probably the most widely used celestial coordinate system, whose equatorial coordinates are: declination () right ascension () -also RA-, or hour angle () -also HA- It is the most closely related to the geographic coordinate system, because they use the same fundamental plane, and the same poles. ... Ground track of the International Space Station for approximately two periods. ... Artists concept of the Interplanetary Transport Network. ... Johannes Keplers primary contributions to astronomy/astrophysics were his three laws of planetary motion. ... A contour plot of the effective potential (the Hills Surfaces) of a two-body system (the Sun and Earth here), showing the five Lagrange points. ... The following is a list of types of orbits: // Box orbit Circular orbit Ecliptic orbit Elliptic orbit Highly Elliptical Orbit Graveyard orbit Hohmann transfer orbit Hyperbolic trajectory Inclined orbit Osculating orbit Parabolic trajectory Capture orbit Escape orbit Semi-synchronous orbit Subsynchronous orbit Synchronous orbit Geocentric orbit Geosynchronous orbit Geostationary orbit... The n-body problem is the problem of finding, given the initial positions, masses, and velocities of n bodies, their subsequent motions as determined by classical mechanics, i. ... In astrodynamics an orbit equation defines the path of orbiting body around central body relative to , without specifying position as a function of time. ... In astrodynamics or celestial dynamics orbital state vectors (sometimes State Vectors) are vectors of position () and velocity () that together with their time (epoch) () uniquely determine the state of an orbiting body. ... Direct motion is the motion of a planetary body in a direction similar to that of other bodies within its system, and is sometimes called prograde motion. ... In astrodynamics the specific orbital energy (or vis-viva energy) of an orbiting body traveling through space under standard assumptions is the sum of its potential energy () and kinetic energy () per unit mass. ... In astrodynamics specific relative angular momentum () of orbiting body () relative to central body () is the relative angular momentum of per unit mass. ...