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Frozen Orbit In orbital mechanics, a frozen orbit is an orbit for an artificial satellite in which natural drifting due to the central body's shape has been minimized by careful selection of the orbital parameters. Typically this is an orbit where, over a long period of time, the altitude remains constant at the same point in each orbit[1] — changes in the inclination, position of the lowest point of the orbit, and eccentricity have been minimized by choosing initial values so that their perturbations cancel out.[2] This results in a longterm stable orbit that minimizes the use of stationkeeping propellant.Contents1 Background and motivation1.1 Lunar frozen orbits2 Classical theory 3 Modern theory 4 Derivation of the closed form expressions for the J3 perturbation 5 References 6 Further readingBackground and motivation[edit] For most spacecraft, changes to orbits are caused by the oblateness of the Earth, gravitational attraction from the sun and moon, solar r [...More...]  "Frozen Orbit" on: Wikipedia Yahoo Parouse 

Orbital Mechanics Orbital mechanics Orbital mechanics or astrodynamics is the application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft. The motion of these objects is usually calculated from Newton's laws of motion Newton's laws of motion and Newton's law of universal gravitation. It is a core discipline within space mission design and control. Celestial mechanics treats more broadly the orbital dynamics of systems under the influence of gravity, including both spacecraft and natural astronomical bodies such as star systems, planets, moons and comets. Orbital mechanics Orbital mechanics focuses on spacecraft trajectories, including orbital maneuvers, orbit plane changes, and interplanetary transfers, and is used by mission planners to predict the results of propulsive maneuvers [...More...]  "Orbital Mechanics" on: Wikipedia Yahoo Parouse 

Envisat Envisat Envisat ("Environmental Satellite") is a large inactive Earthobserving satellite which is still in orbit. Operated by the European Space Agency European Space Agency (ESA), it was the world's largest civilian Earth observation satellite.[2] It was launched on 1 March 2002 aboard an Ariane 5 Ariane 5 from the Guyana Space Centre in Kourou, French Guiana, into a Sun synchronous Sun synchronous polar orbit at an altitude of 790 km (490 mi) (± 10 km or 6.2 mi). It orbits the Earth Earth in about 101 minutes, with a repeat cycle of 35 days [...More...]  "Envisat" on: Wikipedia Yahoo Parouse 

Special Special Special or specials may refer to:Contents1 Music 2 Film and television 3 Other uses 4 See alsoMusic[edit] Special Special (album), a 1992 [...More...]  "Special" on: Wikipedia Yahoo Parouse 

American Institute Of Aeronautics And Astronautics Jim Albaugh Jim Albaugh (President) Sandra Magnus Sandra Magnus (Executive Director)Revenue$ 21 million (2009)Website www.aiaa.orgThe American Institute of Aeronautics and Astronautics American Institute of Aeronautics and Astronautics (AIAA) is a professional society for the field of aerospace engineering. The AIAA was founded in 1963 from the merger of two earlier societies: the American Rocket Society (ARS), founded in 1930 as the American Interplanetary Society (AIS), and the Institute of the Aerospace Sciences (IAS), founded in 1932 as the Institute of the Aeronautical Sciences. AIAA is the U.S [...More...]  "American Institute Of Aeronautics And Astronautics" on: Wikipedia Yahoo Parouse 

Orbital Node An orbital node is either of the two points where an orbit intersects a plane of reference to which it is inclined.[1] A noninclined orbit, which is contained in the reference plane, has no nodes.Contents1 Planes of reference 2 Node distinction 3 Symbols and nomenclature 4 Lunar nodes 5 See also 6 ReferencesPlanes of reference[edit] Common planes of reference include the following:For a geocentric orbit, Earth's equatorial plane. In this case, noninclined orbits are called equatorial.[2] For a heliocentric orbit, the ecliptic or invariable plane. In this case, noninclined orbits are called ecliptic.[2] For an orbit outside the Solar System, the plane through the primary perpendicular to a line through the observer and the primary (called the plane of the sky).[3]Node distinction[edit]Animation about nodes of two elliptic trajectories [...More...]  "Orbital Node" on: Wikipedia Yahoo Parouse 

Reference Ellipsoid In geodesy, a reference ellipsoid is a mathematically defined surface that approximates the geoid, the truer figure of the Earth, or other planetary body. Because of their relative simplicity, reference ellipsoids are used as a preferred surface on which geodetic network computations are performed and point coordinates such as latitude, longitude, and elevation are defined.Contents1 Ellipsoid Ellipsoid parameters 2 Coordinates 3 Historical Earth Earth ellipsoids 4 Ellipsoids for other planetary bodies 5 See also 6 Notes 7 References 8 External links Ellipsoid Ellipsoid parameters[edit] In 1687 Isaac Newton Isaac Newton published the Principia in which he included a proof[1][not in citation given] that a rotating selfgravitating fluid body in equilibrium takes the form of an oblate ellipsoid of revolution which he termed an oblate spheroid [...More...]  "Reference Ellipsoid" on: Wikipedia Yahoo Parouse 

Orbital Perturbation Analysis (spacecraft) Orbital perturbation analysis Orbital perturbation analysis is the activity of determining why a satellite's orbit differs from the mathematical ideal orbit. A satellite's orbit in an ideal twobody system describes a conic section, usually an ellipse. In reality, there are several factors that cause the conic section to continually change [...More...]  "Orbital Perturbation Analysis (spacecraft)" on: Wikipedia Yahoo Parouse 

Kepler Orbit In celestial mechanics, a Kepler orbit Kepler orbit (or Keplerian orbit) is the motion of one body relative to another, as an ellipse, parabola, or hyperbola, which forms a twodimensional orbital plane in threedimensional space. (A Kepler orbit Kepler orbit can also form a straight line.) It considers only the pointlike gravitational attraction of two bodies, neglecting perturbations due to gravitational interactions with other objects, atmospheric drag, solar radiation pressure, a nonspherical central body, and so on. It is thus said to be a solution of a special case of the twobody problem, known as the Kepler problem. As a theory in classical mechanics, it also does not take into account the effects of general relativity [...More...]  "Kepler Orbit" on: Wikipedia Yahoo Parouse 

Figure Of The Earth The figure of the Earth Earth is the size and shape of the Earth Earth in geodesy. Its specific meaning depends on the way it is used and the precision with which the Earth's size and shape is to be defined [...More...]  "Figure Of The Earth" on: Wikipedia Yahoo Parouse 

NASA The National Aeronautics Aeronautics and Space Administration ( NASA NASA /ˈnæsə/) is an independent agency of the executive branch of the United States federal government responsible for the civilian space program, as well as aeronautics and aerospace research.[note 1] President Dwight D. Eisenhower Dwight D. Eisenhower established NASA NASA in 1958[10] with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science [...More...]  "NASA" on: Wikipedia Yahoo Parouse 

Dirk Brouwer Dirk Brouwer (September 1, 1902, Rotterdam Rotterdam – January 31, 1966, New Haven) was a DutchAmerican astronomer.[1] He received his Ph.D. Ph.D. in 1927 at Leiden University Leiden University under Willem de Sitter[2] and then went to Yale University [...More...]  "Dirk Brouwer" on: Wikipedia Yahoo Parouse 

Orbital Perturbation Analysis Orbital perturbation analysis is the activity of determining why a satellite's orbit differs from the mathematical ideal orbit. A satellite's orbit in an ideal twobody system describes a conic section, usually an ellipse. In reality, there are several factors that cause the conic section to continually change [...More...]  "Orbital Perturbation Analysis" on: Wikipedia Yahoo Parouse 

PFS2 Left to right: Mattingly, Young, Duke Apollo program← Apollo 15 Apollo 17 → Apollo 16 Apollo 16 was the tenth manned mission in the United States Apollo space program, the fifth and penultimate to land on the Moon Moon and the first to land in the lunar highlands. The second of the socalled "J missions," it was crewed by Commander John Young, Lunar Module Pilot Charles Duke Charles Duke and Command Module Pilot Ken Mattingly. Launched from the Kennedy Space Center Kennedy Space Center in Florida Florida at 12:54 PM EST on April 16, 1972, the mission lasted 11 days, 1 hour, and 51 minutes, and concluded at 2:45 PM EST on April 27.[2][3][4] Young and Duke spent 71 hours—just under three days—on the lunar surface, during which they conducted three extravehicular activities or moonwalks, totaling 20 hours and 14 minutes [...More...]  "PFS2" on: Wikipedia Yahoo Parouse 

PFS1 1 in cislunar space Plus 4 on the lunar surfaceEVA duration39 minutes, 7 seconds Spacewalk Spacewalk to retrieve film cassettesStart of missionLaunch date July 26, 1971, 13:34:00.6 (19710726UTC13:34Z) UTCRocket Saturn V [...More...]  "PFS1" on: Wikipedia Yahoo Parouse 

Mass Concentration (astronomy) In astronomy and astrophysics, a mass concentration (or mascon) is a region of a planet or moon's crust that contains a large positive gravitational anomaly. In general, the word "mascon" can be used as a noun to refer to an excess distribution of mass on or beneath the surface of an astronomical body (with respect to some suitable average), such as is found around Hawaii Hawaii on Earth.[1] However, this term is most often used to describe a geologic structure that has a positive gravitational anomaly associated with a feature (e.g. depressed basin) that might otherwise have been expected to have a negative anomaly, such as the "mascon basins" on the Moon. Typical examples of mascon basins on the Moon Moon are the Imbrium, Serenitatis, Crisium and Orientale impact basins, all of which exhibit significant topographic depressions and positive gravitational anomalies [...More...]  "Mass Concentration (astronomy)" on: Wikipedia Yahoo Parouse 