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Pioneer Venus Orbiter

The Pioneer Venus Orbiter known as Pioneer Venus 1 or Pioneer 12, was a mission to Venus conducted by the United States as part of the Pioneer Venus project. Launched in May 1978 atop an Atlas-Centaur rocket, the spacecraft was inserted into an elliptical orbit around Venus on December 4, 1978, it returned data on Venus until October 1992. The Pioneer Venus Orbiter was launched by an Atlas SLV-3D Centaur-D1AR rocket, which flew from Launch Complex 36A at the Cape Canaveral Air Force Station; the launch occurred at 13:13:00 on May 20, 1978, deployed the Orbiter into heliocentric orbit for its coast to Venus. Venus orbit insertion occurred on December 4, 1978. Manufactured by Hughes Aircraft Company, the Pioneer Venus Orbiter was based on the HS-507 bus; the spacecraft was 2.5 meters in diameter and 1.2 meters long. All instruments and spacecraft subsystems were mounted on the forward end of the cylinder, except the magnetometer, at the end of a 4.7 meters boom. A solar array extended around the circumference of the cylinder.

A 1.09 metres despun dish antenna provided X band communication with Earth. A Star-24 solid rocket motor was integrated into the spacecraft to provide the thrust to enter orbit around Venus. From Venus orbit insertion to July 1980, periapsis was held between 142 and 253 kilometres to facilitate radar and ionospheric measurements; the spacecraft was in a 24-hour orbit with an apoapsis of 66,900 kilometers. Thereafter, the periapsis was allowed to rise to a maximum of 2,290 kilometres and fall, to conserve fuel. In 1991, the Radar Mapper was reactivated to investigate inaccessible southern portions of the planet, in conjunction with the arrived Magellan spacecraft. In May 1992, Pioneer Venus began the final phase of its mission, in which the periapsis was held between 150 and 250 kilometres, until the spacecraft's propellant was exhausted, after which the orbit decayed naturally; the spacecraft continued to return data until 8 October 1992, with the last signals being received at 19:22 UTC. The Pioneer Venus Orbiter disintegrated upon entering the atmosphere of Venus on October 22, 1992.

The Pioneer Venus Orbiter carried 17 experiments with a total mass of 45 kilograms: a cloud photo-polarimeter to measure the vertical distribution of the clouds, similar to Pioneer 10 and Pioneer 11 imaging photo-polarimeter a surface radar mapper to determine topography and surface characteristics. Observations could only be conducted. A 20 watt S-band signal was sent to the surface that reflected it, with the probe analyzing the echo. Resolution at periapsis was 23 x 7 km. an infrared radiometer to measure IR emissions from Venus' atmosphere an airglow ultraviolet spectrometer to measure scattered and emitted UV light a neutral mass spectrometer to determine the composition of the upper atmosphere a solar wind plasma analyzer to measure properties of the solar wind a magnetometer to characterize the magnetic field at Venus an electric field detector to study the solar wind and its interactions an electron temperature to study the thermal properties of the ionosphere an ion mass spectrometer to characterize the ionospheric ion population a charged particle retarding potential analyzer to study ionospheric particles two radio science experiments to determine the gravity field of Venus a radio occultation experiment to characterize the atmosphere an atmospheric drag experiment to study the upper atmosphere a radio science atmospheric and solar wind turbulence experiment a gamma ray burst detector to record gamma ray burst events The spacecraft conducted radar altimetry observations allowing the first global topographic map of the Venusian surface to be constructed.

From its orbit of Venus, the Pioneer Venus Orbiter was able to observe Halley's Comet when it was unobservable from Earth due to its proximity to the sun during February 1986. UV spectrometer observations monitored the loss of water from the comet's nucleus at perihelion on February 9. Pioneer Venus Multiprobe List of missions to Venus Timeline of artificial satellites and space probes NASA: Pioneer Venus Project Information Pioneer Venus Program Page by NASA's Solar System Exploration Kasprzak, W. T – The Pioneer Venus Orbiter: 11 years of data. – NASA Donahue, T. M.. "Pioneer Venus Results: An Overview". Science. 205: 41–44. Bibcode:1979Sci...205...41D. Doi:10.1126/science.205.4401.41. JSTOR 1748508. PMID 17778895. Colin, Lawrence. "Encounter with Venus: An Update". Science. 205: 44–46. Bibcode:1979Sci...205...44C. doi:10.1126/science.205.4401.44. JSTOR 1748509. PMID 17778896. Seiff, Alvin. "Thermal Contrast in the Atmosphere of Venus: Initial Appraisal from Pioneer Venus Probe Data". Science. 205: 46–49.

Bibcode:1979Sci...205...46S. Doi:10.1126/science.205.4401.46. JSTOR 1748510. Hoffman, J. H.. "Composition and Structure of the Venus Atmosphere: Results from Pioneer Venus". Science. 205: 49–52. Bibcode:1979Sci...205...49H. Doi:10.1126/science.205.4401.49. JSTOR 1748511. PMID 17778898. Oyama, V. I.. B.. "Laboratory Corroboration of the Pioneer Venus Gas Chromatograph Analyses". Science. 205: 52–54. Bibcode:1979Sci...205...52O. Doi:10.1126/science.205.4401.52. JSTOR 1748512. PMID 17778899. Niemann, H. B..

Halved cube graph

In graph theory, the halved cube graph or half cube graph of order n is the graph of the demihypercube, formed by connecting pairs of vertices at distance two from each other in the hypercube graph. That is, it is the half-square of the hypercube; this connectivity pattern produces two isomorphic graphs, disconnected from each other, each of, the halved cube graph. The construction of the halved cube graph can be reformulated in terms of binary numbers; the vertices of a hypercube may be labeled by binary numbers in such a way that two vertices are adjacent when they differ in a single bit. The demicube may be constructed from the hypercube as the convex hull of the subset of binary numbers with an number of nonzero bits, its edges connect pairs of numbers whose Hamming distance is two, it is possible to construct the halved cube graph from a lower-order hypercube graph, without taking a subset of the vertices: 1 2 Q n = Q n − 1 2 where the superscript 2 denotes the square of the hypercube graph Qn − 1, the graph formed by connecting pairs of vertices whose distance is at most two in the original graph.

For instance, the halved cube graph of order four may be formed from an ordinary three-dimensional cube by keeping the cube edges and adding edges connecting pairs of vertices that are on opposite corners of the same square face. The halved cube graph 1 2 Q 3 of order 3 is the complete graph K4, the graph of the tetrahedron; the halved cube graph 1 2 Q 4 of order 4 is K2,2,2,2, the graph of the four-dimensional regular polytope, the 16-cell. The halved cube graph 1 2 Q 5 of order five is sometimes known as the Clebsch graph, is the complement of the folded cube graph of order five, more called the Clebsch graph, it exists in the 5-demicube. Because it is the bipartite half of a distance-regular graph, the halved cube graph is itself distance-regular, and because it contains a hypercube as a spanning subgraph, it inherits from the hypercube all monotone graph properties, such as the property of containing a Hamiltonian cycle. As with the hypercube graphs, their isometric subgraphs the partial cubes, a halved cube graph may be embedded isometrically into a real vector space with the Manhattan metric.

The same is true for the isometric subgraphs of halved cube graphs, which may be recognized in polynomial time. For every halved cube graph of order five or more, it is possible to color the vertices with two colors, in such a way that the resulting colored graph has no nontrivial symmetries. For the graphs of order three and four, four colors are needed to eliminate all symmetries; the two graphs shown are symmetric Dn and Bn Petrie polygon projections of the related polytope which can include overlapping edges and vertices. Weisstein, Eric W. "Halved Cube Graph". MathWorld

Antoine Duhamel

Antoine Duhamel was a French composer, orchestra conductor and music teacher. Born in Valmondois in the Val-d'Oise département of France, Antoine Duhamel was the son of the French writer Georges Duhamel and actress Blanche Albane, he studied music at the Sorbonne. He was a pupil of René Leibowitz, an exponent of Arnold Schoenberg’s dodecaphonic and serial method of composing. Together with other Leibowitz pupils, Serge Nigg, André Casanova and Jean Prodromidès, he gave the first performance of Leibowitz's Explications des Metaphors, Op. 15, in Paris in 1948. He wrote the score for his first film in 1960, going on to work with many of Europe's film directors. In 2002 he was awarded the Silver Bear at the Berlin Film Festival for his music for the Bertrand Tavernier directed film, Laissez-passer. Duhamel scored several of Jean-Luc Godard's films, including Week End, he died at the age of 89 in September 2014. 1964: The Pit and the Pendulum 1965: Pierrot le Fou 1966: Trap for the Assassin 1966: La Longue marche 1966: La Voleuse 1967: The Sailor from Gibraltar 1967: Weekend 1968: Stolen Kisses 1969: Mississippi Mermaid 1970: Bed and Board 1970: The Cop 1973: Frank en Eva 1978: The Song of Roland 1979: Mais ou et donc Ornicar 1979: Return to the Beloved 1980: Death Watch 1989: El sueño del mono loco 1994: La Piste du télégraphe 1996: Ridicule 1998: The Girl of Your Dreams 2002: Safe Conduct Gravel Pit Antoine Duhamel on IMDb Alfred Duhamel French language Wikipedia article