1.
Venus
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Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. It has the longest rotation period of any planet in the Solar System and it is named after the Roman goddess of love and beauty. It is the second-brightest natural object in the sky after the Moon, reaching an apparent magnitude of −4.6. Because Venus orbits within Earths orbit it is a planet and never appears to venture far from the Sun. Venus is a planet and is sometimes called Earths sister planet because of their similar size, mass, proximity to the Sun. It is radically different from Earth in other respects and it has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. The atmospheric pressure at the surface is 92 times that of Earth. Venus is by far the hottest planet in the Solar System, with a surface temperature of 735 K. Venus is shrouded by an layer of highly reflective clouds of sulfuric acid. It may have had water oceans in the past, but these would have vaporized as the temperature rose due to a greenhouse effect. The water has probably photodissociated, and the hydrogen has been swept into interplanetary space by the solar wind because of the lack of a planetary magnetic field. Venuss surface is a dry desertscape interspersed with rocks and is periodically resurfaced by volcanism. As one of the brightest objects in the sky, Venus has been a fixture in human culture for as long as records have existed. It has been sacred to gods of many cultures, and has been a prime inspiration for writers and poets as the morning star. Venus was the first planet to have its motions plotted across the sky, as the closest planet to Earth, Venus has been a prime target for early interplanetary exploration. It was the first planet beyond Earth visited by a spacecraft, Venuss thick clouds render observation of its surface impossible in visible light, and the first detailed maps did not emerge until the arrival of the Magellan orbiter in 1991. Plans have been proposed for rovers or more missions. Venus is one of the four planets in the Solar System
2.
NASA
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President Dwight D. Eisenhower established NASA in 1958 with a distinctly civilian orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29,1958, disestablishing NASAs predecessor, the new agency became operational on October 1,1958. Since that time, most US space exploration efforts have led by NASA, including the Apollo Moon landing missions, the Skylab space station. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle, the agency is also responsible for the Launch Services Program which provides oversight of launch operations and countdown management for unmanned NASA launches. NASA shares data with various national and international such as from the Greenhouse Gases Observing Satellite. Since 2011, NASA has been criticized for low cost efficiency, from 1946, the National Advisory Committee for Aeronautics had been experimenting with rocket planes such as the supersonic Bell X-1. In the early 1950s, there was challenge to launch a satellite for the International Geophysical Year. An effort for this was the American Project Vanguard, after the Soviet launch of the worlds first artificial satellite on October 4,1957, the attention of the United States turned toward its own fledgling space efforts. This led to an agreement that a new federal agency based on NACA was needed to conduct all non-military activity in space. The Advanced Research Projects Agency was created in February 1958 to develop technology for military application. On July 29,1958, Eisenhower signed the National Aeronautics and Space Act, a NASA seal was approved by President Eisenhower in 1959. Elements of the Army Ballistic Missile Agency and the United States Naval Research Laboratory were incorporated into NASA, earlier research efforts within the US Air Force and many of ARPAs early space programs were also transferred to NASA. In December 1958, NASA gained control of the Jet Propulsion Laboratory, NASA has conducted many manned and unmanned spaceflight programs throughout its history. Some missions include both manned and unmanned aspects, such as the Galileo probe, which was deployed by astronauts in Earth orbit before being sent unmanned to Jupiter, the experimental rocket-powered aircraft programs started by NACA were extended by NASA as support for manned spaceflight. This was followed by a space capsule program, and in turn by a two-man capsule program. This goal was met in 1969 by the Apollo program, however, reduction of the perceived threat and changing political priorities almost immediately caused the termination of most of these plans. NASA turned its attention to an Apollo-derived temporary space laboratory, to date, NASA has launched a total of 166 manned space missions on rockets, and thirteen X-15 rocket flights above the USAF definition of spaceflight altitude,260,000 feet. The X-15 was an NACA experimental rocket-powered hypersonic research aircraft, developed in conjunction with the US Air Force, the design featured a slender fuselage with fairings along the side containing fuel and early computerized control systems
3.
Ames Research Center
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Ames Research Center, also known as NASA Ames, is a major NASA research center at Moffett Federal Airfield in Californias Silicon Valley. It was founded as the second National Advisory Committee for Aeronautics laboratory and that agency was dissolved and its assets and personnel transferred to the newly created National Aeronautics and Space Administration on October 1,1958. NASA Ames is named in honor of Joseph Sweetman Ames, a physicist, at last estimate NASA Ames has over US$3.0 billion in capital equipment,2,300 research personnel and a US$860 million annual budget. Ames was founded to conduct research on the aerodynamics of propeller-driven aircraft, however, its role has expanded to encompass spaceflight. Ames plays a role in many NASA missions, Ames also develops tools for a safer, more efficient national airspace. The centers current director is Eugene Tu, the site is mission center for several key current missions and a major contributor to the new exploration focus as a participant in the Orion crew exploration vehicle. Although Ames is a NASA Research Center, and not a center, it has nevertheless been closely involved in a number of astronomy. The Pioneer programs eight successful missions from 1965 to 1978 were managed by Charles Hall at Ames. By 1972, it supported the bold flyby missions to Jupiter and Saturn with Pioneer 10 and those two missions were trail blazers for the planners of the more complex Voyager 1 and Voyager 2 missions, launched five years later. In 1978, the end of the program brought about a return to the solar system, with the Pioneer Venus Orbiter and Multiprobe. Lunar Prospector was the mission selected by NASA for full development. Based on Lunar Prospector Neutron Spectrometer data, mission scientists have determined that there is indeed water ice in the craters of the Moon. The 11-pound GeneSat-1, carrying bacteria inside a laboratory, was launched on December 16,2006. The very small NASA satellite has proven that scientists can quickly design, the Lunar Crater Observation and Sensing Satellite mission to look for water on the moon was a secondary payload spacecraft. LCROSS began its trip to the moon on the rocket as the Lunar Reconnaissance Orbiter. It launched in April 2009 on an Atlas V rocket from Kennedy Space Center, the Kepler mission is NASAs first mission capable of finding Earth-size and smaller planets. The Kepler mission will monitor the brightness of stars to find planets that pass in front of them during the planets orbits, during such passes or transits, the planets will slightly decrease the stars brightness. Stratospheric Observatory for Infrared Astronomy is a joint venture of the U. S, the aircraft is supplied by the U. S. and the infrared telescope by Germany
4.
Satellite bus
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A satellite bus or spacecraft bus is the general model on which multiple-production satellite spacecraft are often based. The bus is the infrastructure of a spacecraft, usually providing locations for the payload, a bus-derived satellite would be used as opposed to a one-off, or specially produced satellite, such as Prospero X-3. Bus-derived satellites are usually customized to customer requirements, for example with specialized sensors or transponders, comparison of satellite buses Service module Satellite Glossary JWST Observatory, The Spacecraft Bus Spitzers Spacecraft Bus Gunters Space Page, Spacecraft buses
5.
Spacebus
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Spacebus is a satellite bus produced at the Cannes Mandelieu Space Center in France by Thales Alenia Space. Spacebuses are typically used for communications satellites, and seventy-four have been launched since development started in the 1980s. Spacebus was originally produced by Aérospatiale and later passed to Alcatel Alenia Space, in 2006, it was sold to Thales Group as Thales Alenia Space. The first Spacebus satellite, Arabsat-1A, was launched in 1985, since then, seventy-four have been launched, with one more completed, and six outstanding orders. The launch of the 50th Spacebus satellite, Star One C1 and it was a Spacebus 3000B3, launched by an Ariane 5 rocket flying from the Guiana Space Centre in Kourou, French Guiana. Aérospatiale had produced a number of satellites, including Symphonie, with the German company Messerschmitt, on 9 December 1983, the two companies signed the Franco-German Spacebus Agreement. The Spacebus designation was first applied to satellites which were under construction by Aérospatiale when the programme started, later series names were followed by a number indicating the approximate mass of the bus in kilograms. Spacebus designations were not applied retrospectively to satellites which had already been launched, the bus was designed to be adaptable to perform various missions, however, as of 2009, only communications satellites have been ordered. It was also designed to be adaptable when the capacity of launch systems increased, the bus is made of carbon fibre with a composite honeycomb structure. It contains fuel tanks, equipment needed to interface with a carrier rocket, panels are attached to the outside of the structure with externally mounted equipment, including the solar panels, payload, and engine. The payload, which is developed separately from the bus, takes up three panels, once it has been outfitted with transponders or other equipment, it is transported to Cannes-Mandelieu, where it is integrated onto the bus. The satellites are powered by solar panels. Several configurations are used depending on the amount of power that the satellite is expected to require, the batteries used to store this power are produced by the Belgian company ETCA. Early satellites used nickel-hydrogen batteries, while later spacecraft use lithium-ion batteries, Spacebus satellites use bipropellant, liquid-fuelled chemical engines to achieve their orbits, and subsequently perform station-keeping. Electric propulsion was used on the Stentor and Astra 1K satellites, Spacebus Neo will be an electric propulsion satellite. A three-axis stabilisation system is used for attitude control, Spacebus satellites were developed to be compatible with a large number of available carrier rockets, particularly the Ariane family of rockets. As the performance of the Ariane has increased, the satellites have become larger to take advantage of increased capacity. Three Spacebus 100 satellites were produced for Arabsat, to serve the 22 members of the Arab League, One of the solar panels on the first satellite, Arabsat-1A, failed to deploy resulting in reduced power to the spacecraft
6.
Hughes Aircraft Company
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The Hughes Aircraft Company was a major American aerospace and defense contractor founded in 1932 by Howard Hughes in Glendale, California as a division of Hughes Tool Company. During World War II the company designed and built prototype aircraft at Hughes Airport. These included the famous Hughes H-4 Hercules, better known by the nickname for it, the Spruce Goose, the H-1 racer, D-2. At the start of the war Hughes Aircraft had only four full-time employees—by the end the number was 80,000. Hughes Aircraft was one of many aerospace and defense companies which flourished in Southern California during, by the summer of 1947 certain politicians had become concerned about Hughes alleged mismanagement of the Spruce Goose and the XF-11 photo reconnaissance plane project. They formed a committee to investigate Hughes which culminated in a much-followed Senate investigation. Despite a highly critical report, Hughes was cleared. In 1948 Hughes created a new division of the company, the Aerospace Group, two Hughes engineers, Simon Ramo and Dean Wooldridge, had new ideas on the packaging of electronics to make complete fire control systems. Their MA-1 system combined signals from the radar with a digital computer to automatically guide the interceptor aircraft into the proper position for firing missiles. At the same time other teams were working with the newly formed US Air Force on air-to-air missiles, delivering the AIM-4 Falcon, the MA-1/Falcon package, with several upgrades, was the primary interceptor weapon system of the USAF for many years, lasting into the 1980s. The company became TRW in 1965, another company and a major competitor to Hughes Aircraft. In 1951 Hughes Aircraft Co. built a plant in Tucson. By the end of year, the U. S. Air Force had purchased the property. This Tucson plant is still in operation under the ownership of Raytheon Co, Howard Hughes donated Hughes Aircraft to the newly formed Howard Hughes Medical Institute in 1953 allegedly as a way of avoiding taxes on its huge income. Pat Hyland was hired as president and general manager of Hughes Aircraft, he would ultimately become company president. Under Hylands guidance, the Aerospace Group continued to diversify and become massively profitable, the company developed radar systems, electro-optical systems, the first working laser, aircraft computer systems, missile systems, ion-propulsion engines, and many other advanced technologies. The Electronic Properties Information Center of the United States was hosted at the Hughes Culver City library in the 1970s, EPIC published the multi-volume Handbook of Electronic Materials as public documents. Greg Jarvis and Ronald McNair, two of the astronauts on the last flight of the Space Shuttle Challenger, were Hughes alumni, Hughes Aircraft Ground Systems Group was located in Fullerton, California
7.
Atlas-Centaur
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The Atlas-Centaur was an American expendable launch system derived from the SM-65 Atlas D missile. Launches were conducted from Launch Complex 36 at Cape Canaveral Air Force Station, Convair, the manufacturer of the Atlas, developed the Centaur upper stage specifically for that booster, sharing its inflated balloon skin. It was also the first production rocket stage to liquid hydrogen. Despite high performance, LH2 nonetheless had problems because it had to be chilled at extremely low temperatures, however, the progress made during the aborted venture was picked up by Convair and others for rocket stage use. Although originally under ARPA supervision, Centaur was transferred to NASA in July 1959, however, the Air Force retained ultimate supervision in part because they intended to use Centaur for an ambitious network of military communications satellites known as ADVENT. A constellation of ten satellites would provide round-the-clock instant communications for the three branches of the US military. The first three would be launched on an Atlas-Agena, then the remainder on Centaur, ADVENT never got off the drawing board, but Centaur quickly found a use for several NASA planetary probe projects, namely Mariner and Surveyor. Centaur development was somewhat difficult by the insistence on modifying Atlas components rather than develop totally new ones. This was done for time and budget reasons and because it allowed the Centaur to be manufactured on the existing Atlas assembly line at Convair, the engines were manufactured by Pratt and Whitney. He preferred the use of a Saturn-Agena combo for planetary probes and this and lack of funds caused the project to drag on far longer than intended. Under original timetables, Centaur was to make its first flight in January 1961, in April, NASA Lunar and Planetary Programs director Oran Nicks suggested that it might be necessary to use Atlas-Agena for Mariner instead. By September, there was no launch date anywhere in sight while program costs rose higher and higher, the first Atlas-Centaur, Vehicle F-1, arrived at Cape Canaveral in October 1961 and was erected at the newly completed LC-36A, a pad built specifically for A/C flights. Flight plans amounted to more than a single burn with a partially fueled Centaur. The mission at last got under way on 8 May 1962, all went well until about T+53 seconds when the Centaur stage ruptured and disintegrated, taking the Atlas with it in a matter of seconds. It was unclear what had caused the failure at first, as tracking camera footage showed a large white cloud enveloping the booster followed by explosion of the entire launch vehicle. Scott Carpenters Mercury flight was only days away, and if the failure were caused by the Atlas, it could mean significant delays for that mission, which used a similar Atlas D derived booster. However, analysis of data and closer examination of the launch films quickly confirmed the Centaur as the source of trouble. The failure was determined to be caused by a panel that ripped off the Centaur during ascent, causing the LH2 to overheat
8.
Cape Canaveral Air Force Station
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Cape Canaveral Air Force Station is an installation of the United States Air Force Space Commands 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in Brevard County, Florida, CCAFS is the primary head of Americas Eastern Range with three launch pads currently active. The Cape Canaveral Air Force Station Skid Strip provides a 10, 000-foot runway close to the launch complexes for military airlift aircraft delivering heavy, a number of American space exploration firsts were launched from CCAFS, including the first U. S. Earth satellite, first U. S. astronaut, first U. S. astronaut in orbit, first two-man U. S. spacecraft, first U. S. unmanned lunar landing, and first three-man U. S. spacecraft. The CCAFS area had used by the United States government to test missiles since 1949. On June 1,1948, the U. S. Navy transferred the former Banana River Naval Air Station to the U. S. Air Force, with USAF renaming the facility the Joint Long Range Proving Ground Base on June 10,1949. On October 1,1949, the Joint Long Range Proving Ground Base was transferred from the Air Materiel Command to the Air Force Division of the Joint Long Range Proving Ground. On May 17,1950, the base was renamed the Long Range Proving Ground Base, in 1951, the Air Force established the Air Force Missile Test Center. Early American sub-orbital rocket flights were achieved at Cape Canaveral in 1956 and these flights occurred shortly after sub-orbital flights launched from White Sands Missile Range, such as the Viking 12 sounding rocket on February 4,1955. Following the Soviet Unions successful Sputnik 1, the US attempted its first launch of a satellite from Cape Canaveral on December 6,1957. However, the rocket carrying Vanguard TV3 blew up on the launch pad, NASA was founded in 1958, and Air Force crews launched missiles for NASA from the Cape, known then as Cape Canaveral Missile Annex. The row of Titan and Atlas launch pads along the coast came to be known as Missile Row in the 1960s, nASAs first manned spaceflight program was prepared for launch from Canaveral by U. S. Air Force crews. Mercurys objectives were to place a spacecraft in Earth orbit, investigate human performance and ability to function in space. Suborbital flights were launched by derivatives of the Armys Redstone missile from LC-5, Orbital flights were launched by derivatives of the Air Forces larger Atlas D missile from LC-14. The first American in orbit was John Glenn on February 20,1962, three more orbital flights followed through May 1963. Flight control for all Mercury missions was provided at the Mercury Control Center located at Canaveral near LC-14 and he had also convinced Gov. C. Farris Bryant to change the name of Cape Canaveral to Cape Kennedy and this resulted in some confusion in public perception, which conflated the two. This name was used through the Gemini and early Apollo programs, however, the geographical name change proved to be unpopular, owing to the historical longevity of Cape Canaveral
9.
Spaceport Florida Launch Complex 36
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Launch Complex 36 —formerly known as Space Launch Complex 36 from 1997 to 2010—is a launch complex at Cape Canaveral Air Force Station in Brevard County, Florida. It was used for Atlas launches by NASA and the US Air Force from 1962 until 2005, Blue Origin has leased the launch site since 2015 in order to build a new launch site for launching Blues orbital rockets. Orbital launches are expected to begin from LC36 no earlier than 2020, historically, the complex consisted of two launch pads, SLC-36A and SLC-36B, and was the launch site for the Pioneer, Surveyor, and Mariner probes in the 1960s and 1970s. There were a total of 68 and 77 launches from pads 36A and 36B, respectively, the Atlas rockets launched from Complex 36 were subsequently replaced by the Atlas V launch vehicle which launches from Complex 41 at Cape Canaveral beginning in 2002. LC-36A was the scene of the biggest on-pad explosion in Cape history when Atlas-Centaur AC-5 fell back onto the pad on March 2,1965, the accident spurred NASA to complete work on LC-36B which had been abandoned when it was 90% finished. In March 2010, the USAF 45th Space Wing issued Real Property Licenses to Space Florida for Space Launch Complexes 36 and 46 at Cape Canaveral Air Force Station. Moon Express leased the pad in February 2015 from Space Florida as a development and test site for its commercial lunar operations, as of 2016, orbital launches are expected to begin from LC-36 no earlier than 2020. The legacy Atlas-Centaur umbilical towers of both pads were demolished in 2006, the mobile service towers were both demolished in controlled explosions on June 16,2007. Tower B was demolished at 13,59 GMT and tower A followed twelve minutes later at 14,11, on September 15,2015, Blue Origin announced it would use Launch Complex 36 for launches of its orbital launch vehicle later in the decade. As of 2015, the first Blue launch from LC36 was planned for before 2020, as of October 2015, the pad design and configuration was not yet known. Blue broke ground for the facility to initiate construction activity on the site in June 2016, the New Glenn will be a very large 7. 0-meter -diameter vehicle. The first stage will be powered by seven BE-4 methane/oxygen engines producing 17.1 meganewtons total thrust at launch, the first stage will be reusable and is designed to land vertically. List of Cape Canaveral and Merritt Island launch sites Patrick Air Force Base
10.
Semi-major and semi-minor axes
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In geometry, the major axis of an ellipse is its longest diameter, a line segment that runs through the center and both foci, with ends at the widest points of the perimeter. The semi-major axis is one half of the axis, and thus runs from the centre, through a focus. Essentially, it is the radius of an orbit at the two most distant points. For the special case of a circle, the axis is the radius. One can think of the axis as an ellipses long radius. The semi-major axis of a hyperbola is, depending on the convention, thus it is the distance from the center to either vertex of the hyperbola. A parabola can be obtained as the limit of a sequence of ellipses where one focus is fixed as the other is allowed to move arbitrarily far away in one direction. Thus a and b tend to infinity, a faster than b, the semi-minor axis is a line segment associated with most conic sections that is at right angles with the semi-major axis and has one end at the center of the conic section. It is one of the axes of symmetry for the curve, in an ellipse, the one, in a hyperbola. The semi-major axis is the value of the maximum and minimum distances r max and r min of the ellipse from a focus — that is. In astronomy these extreme points are called apsis, the semi-minor axis of an ellipse is the geometric mean of these distances, b = r max r min. The eccentricity of an ellipse is defined as e =1 − b 2 a 2 so r min = a, r max = a. Now consider the equation in polar coordinates, with one focus at the origin, the mean value of r = ℓ / and r = ℓ /, for θ = π and θ =0 is a = ℓ1 − e 2. In an ellipse, the axis is the geometric mean of the distance from the center to either focus. The semi-minor axis of an ellipse runs from the center of the ellipse to the edge of the ellipse, the semi-minor axis is half of the minor axis. The minor axis is the longest line segment perpendicular to the axis that connects two points on the ellipses edge. The semi-minor axis b is related to the axis a through the eccentricity e. A parabola can be obtained as the limit of a sequence of ellipses where one focus is fixed as the other is allowed to move arbitrarily far away in one direction
11.
Orbital eccentricity
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The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is an orbit, values between 0 and 1 form an elliptical orbit,1 is a parabolic escape orbit. The term derives its name from the parameters of conic sections and it is normally used for the isolated two-body problem, but extensions exist for objects following a rosette orbit through the galaxy. In a two-body problem with inverse-square-law force, every orbit is a Kepler orbit, the eccentricity of this Kepler orbit is a non-negative number that defines its shape. The limit case between an ellipse and a hyperbola, when e equals 1, is parabola, radial trajectories are classified as elliptic, parabolic, or hyperbolic based on the energy of the orbit, not the eccentricity. Radial orbits have zero angular momentum and hence eccentricity equal to one, keeping the energy constant and reducing the angular momentum, elliptic, parabolic, and hyperbolic orbits each tend to the corresponding type of radial trajectory while e tends to 1. For a repulsive force only the trajectory, including the radial version, is applicable. For elliptical orbits, a simple proof shows that arcsin yields the projection angle of a circle to an ellipse of eccentricity e. For example, to view the eccentricity of the planet Mercury, next, tilt any circular object by that angle and the apparent ellipse projected to your eye will be of that same eccentricity. From Medieval Latin eccentricus, derived from Greek ἔκκεντρος ekkentros out of the center, from ἐκ- ek-, eccentric first appeared in English in 1551, with the definition a circle in which the earth, sun. Five years later, in 1556, a form of the word was added. The eccentricity of an orbit can be calculated from the state vectors as the magnitude of the eccentricity vector, e = | e | where. For elliptical orbits it can also be calculated from the periapsis and apoapsis since rp = a and ra = a, where a is the semimajor axis. E = r a − r p r a + r p =1 −2 r a r p +1 where, rp is the radius at periapsis. For Earths annual orbit path, ra/rp ratio = longest_radius / shortest_radius ≈1.034 relative to center point of path, the eccentricity of the Earths orbit is currently about 0.0167, the Earths orbit is nearly circular. Venus and Neptune have even lower eccentricity, over hundreds of thousands of years, the eccentricity of the Earths orbit varies from nearly 0.0034 to almost 0.058 as a result of gravitational attractions among the planets. The table lists the values for all planets and dwarf planets, Mercury has the greatest orbital eccentricity of any planet in the Solar System. Such eccentricity is sufficient for Mercury to receive twice as much solar irradiation at perihelion compared to aphelion, before its demotion from planet status in 2006, Pluto was considered to be the planet with the most eccentric orbit
12.
Apsis
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An apsis is an extreme point in an objects orbit. The word comes via Latin from Greek and is cognate with apse, for elliptic orbits about a larger body, there are two apsides, named with the prefixes peri- and ap-, or apo- added to a reference to the thing being orbited. For a body orbiting the Sun, the point of least distance is the perihelion, the terms become periastron and apastron when discussing orbits around other stars. For any satellite of Earth including the Moon the point of least distance is the perigee, for objects in Lunar orbit, the point of least distance is the pericynthion and the greatest distance the apocynthion. For any orbits around a center of mass, there are the terms pericenter and apocenter, periapsis and apoapsis are equivalent alternatives. A straight line connecting the pericenter and apocenter is the line of apsides and this is the major axis of the ellipse, its greatest diameter. For a two-body system the center of mass of the lies on this line at one of the two foci of the ellipse. When one body is larger than the other it may be taken to be at this focus. Historically, in systems, apsides were measured from the center of the Earth. In orbital mechanics, the apsis technically refers to the distance measured between the centers of mass of the central and orbiting body. However, in the case of spacecraft, the family of terms are used to refer to the orbital altitude of the spacecraft from the surface of the central body. The arithmetic mean of the two limiting distances is the length of the axis a. The geometric mean of the two distances is the length of the semi-minor axis b, the geometric mean of the two limiting speeds is −2 ε = μ a which is the speed of a body in a circular orbit whose radius is a. The words pericenter and apocenter are often seen, although periapsis/apoapsis are preferred in technical usage, various related terms are used for other celestial objects. The -gee, -helion and -astron and -galacticon forms are used in the astronomical literature when referring to the Earth, Sun, stars. The suffix -jove is occasionally used for Jupiter, while -saturnium has very rarely used in the last 50 years for Saturn. The -gee form is used as a generic closest approach to planet term instead of specifically applying to the Earth. During the Apollo program, the terms pericynthion and apocynthion were used when referring to the Moon, regarding black holes, the term peri/apomelasma was used by physicist Geoffrey A. Landis in 1998 before peri/aponigricon appeared in the scientific literature in 2002
13.
Orbital inclination
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Orbital inclination measures the tilt of an objects orbit around a celestial body. It is expressed as the angle between a plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Earth directly above the equator, the plane of the orbit is the same as the Earths equatorial plane. The general case is that the orbit is tilted, it spends half an orbit over the northern hemisphere. If the orbit swung between 20° north latitude and 20° south latitude, then its orbital inclination would be 20°, the inclination is one of the six orbital elements describing the shape and orientation of a celestial orbit. It is the angle between the plane and the plane of reference, normally stated in degrees. For a satellite orbiting a planet, the plane of reference is usually the plane containing the planets equator, for planets in the Solar System, the plane of reference is usually the ecliptic, the plane in which the Earth orbits the Sun. This reference plane is most practical for Earth-based observers, therefore, Earths inclination is, by definition, zero. Inclination could instead be measured with respect to another plane, such as the Suns equator or the invariable plane, the inclination of orbits of natural or artificial satellites is measured relative to the equatorial plane of the body they orbit, if they orbit sufficiently closely. The equatorial plane is the perpendicular to the axis of rotation of the central body. An inclination of 30° could also be described using an angle of 150°, the convention is that the normal orbit is prograde, an orbit in the same direction as the planet rotates. Inclinations greater than 90° describe retrograde orbits, thus, An inclination of 0° means the orbiting body has a prograde orbit in the planets equatorial plane. An inclination greater than 0° and less than 90° also describe prograde orbits, an inclination of 63. 4° is often called a critical inclination, when describing artificial satellites orbiting the Earth, because they have zero apogee drift. An inclination of exactly 90° is an orbit, in which the spacecraft passes over the north and south poles of the planet. An inclination greater than 90° and less than 180° is a retrograde orbit, an inclination of exactly 180° is a retrograde equatorial orbit. For gas giants, the orbits of moons tend to be aligned with the giant planets equator, the inclination of exoplanets or members of multiple stars is the angle of the plane of the orbit relative to the plane perpendicular to the line-of-sight from Earth to the object. An inclination of 0° is an orbit, meaning the plane of its orbit is parallel to the sky. An inclination of 90° is an orbit, meaning the plane of its orbit is perpendicular to the sky
14.
Pioneer program
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The Pioneer program is a series of United States unmanned space missions that were designed for planetary exploration. There were a number of missions in the program, but the most notable were Pioneer 10 and Pioneer 11. Pioneer 10 and Pioneer 11 carry a golden plaque, depicting a man and a woman and information about the origin and the creators of the probes, should any extraterrestrials find them someday. Credit for naming the first probe has been attributed to Stephen A. Saliga, while he was at a briefing, the spacecraft was described to him as a lunar-orbiting vehicle with an infrared scanning device. Saliga thought the title too long and lacked theme for an exhibit design, the earliest missions were attempts to achieve Earths escape velocity, simply to show it was feasible and study the Moon. This included the first launch by NASA which was formed from the old NACA and these missions were carried out by the US Air Force and Army. Most missions here are listed with their most recognised name, while successful, the missions returned much poorer images than the Voyager program probes would five years later. In 1978, the end of the program saw a return to the inner Solar System, with the Pioneer Venus Orbiter and Multiprobe, the new missions were numbered from Pioneer 6.8 AU distance to the Sun. Their orbital periods are slightly shorter than Earths. Pioneer 7 and Pioneer 8 are in orbits with 1.1 AU distance to the Sun. Their orbital periods are slightly longer than Earths. Since the probes orbital periods differ from that of the Earth, from time to time, the probes can sense parts of the Sun several days before the Suns rotation reveals it to ground-based Earth orbiting observatories. If a powerful solar magnetic storm is formed, they can warn Earth in advance, Pioneer 10 – Jupiter, interstellar medium, launched March 1972 Pioneer 11 – Jupiter, Saturn, interstellar medium, launched April 1973 Pioneer H – identical to Pioneers 10 and 11. Proposed out-of-the-ecliptic mission for 1974, but was not built
15.
Pioneer Venus project
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The Pioneer Venus project was part of the Pioneer program consisting of two spacecraft, the Pioneer Venus Orbiter and the Pioneer Venus Multiprobe, launched to Venus in 1978. The program was managed by NASAs Ames Research Center, the Pioneer Venus Orbiter entered orbit around Venus on December 4,1978, and performed observations to characterize the atmosphere and surface of Venus. It continued to transmit data until October 1992, the Pioneer Venus Multiprobe deployed four small probes into the Venusian atmosphere on December 9,1978. All four probes transmitted data throughout their descent to the surface, one probe survived landing and transmitted data from the surface for over an hour. The Pioneer mission consisted of two components, launched separately, an orbiter and a multiprobe, the orbiter was launched on 20 May 1978 with an Atlas-Centaur rocket. The orbiters mass was 517 kg, the Pioneer Venus Orbiter was inserted into an elliptical orbit around Venus on December 4,1978. The Pioneer Venus Multiprobe was launched on August 8,1978 on an Atlas-Centaur rocket and it consisted of a 290 kg bus which carried one large and three small atmospheric probes. The large probe was released on November 16,1978 and the three small probes on November 20, all four probes entered the Venus atmosphere on December 9, followed by the bus. The Pioneer Venus large probe was about 1.5 m in diameter, after deceleration from initial atmospheric entry at about 11.5 km/s, a parachute was deployed at 47 km altitude.8 m in diameter and 90 kg each small probe. The small probes were each targeted at different parts of the planet, They had no parachutes, the Pioneer Venus bus also carried two experiments, a neutral mass spectrometer and an ion mass spectrometer to study the composition of the atmosphere. With no heat shield or parachute, the bus made measurements only to about 110 km altitude before burning up, Pioneer Venus specifications at NASA The Pioneer Venus Orbiter,11 years of data. Results published in May 1,1990
16.
Pioneer 11
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It was the first probe to encounter Saturn and the second to fly through the asteroid belt and by Jupiter. Due to power constraints and the vast distance to the probe, approved in February 1969, Pioneer 11 and its twin probe, Pioneer 10, were the first to be designed for exploring the outer Solar System. Subsequent planning for an encounter with Saturn added many more goals, Map the magnetic field of Saturn and determine its intensity, direction, determine how many electrons and protons of various energies are distributed along the trajectory of the spacecraft through the Saturn system. Map the interaction of the Saturn system with the solar wind, measure the temperature of Saturns atmosphere and that of Titan, the largest satellite of Saturn. Determine the structure of the atmosphere of Saturn where molecules are expected to be electrically charged. Map the thermal structure of Saturns atmosphere by infrared observations coupled with radio occultation data, obtain spin-scan images of the Saturnian system in two colors during the encounter sequence and polarimetry measurements of the planet. Probe the ring system and the atmosphere of Saturn with S-band radio occultation, determine more precisely the masses of Saturn and its larger satellites by accurate observations of the effects of their gravitational fields on the motion of the spacecraft. As a precursor to the Mariner Jupiter/Saturn mission, verify the environment of the plane to find out where it may be safely crossed by the Mariner spacecraft without serious damage. Pioneer 11 was built by TRW and managed as part of the Pioneer program by NASA Ames Research Center, a backup unit, Pioneer H, is currently on display in the Milestones of Flight exhibit at the National Air and Space Museum in Washington, D. C. Many elements of the proved to be critical in the planning of the Voyager Program. The Pioneer 11 bus measured 36 centimeters deep and with six 76-centimeter-long panels forming the hexagonal structure, the bus housed propellant to control the orientation of the probe and eight of the twelve scientific instruments. The spacecraft had a mass of 260 kilograms, information for the orientation was provided by performing conical scanning maneuvers to track Earth in its orbit, a star sensor able to reference Canopus, and two Sun sensors. The space probe included a redundant system transceivers, one attached to the high-gain antenna, each transceiver was 8 watts and transmitted data across the S-band using 2110 MHz for the uplink from Earth and 2292 MHz for the downlink to Earth with the Deep Space Network tracking the signal. Prior to transmitting data, the probe used an encoder to allow correction of errors in the received data on Earth. Pioneer 11 used four SNAP-19 radioisotope thermoelectric generators and they were positioned on two three-rod trusses, each 3 meters in length and 120 degrees apart. This was expected to be a distance from the sensitive scientific experiments carried on board. Combined, the RTGs provided 155 watts at launch, and decayed to 140 W in transit to Jupiter, the spacecraft required 100 W to power all systems. The spacecraft included two command decoders and a distribution unit, a very limited form of processor, to direct operations on the spacecraft
17.
Pioneer Venus Multiprobe
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The Pioneer Venus Multiprobe, also known as Pioneer Venus 2 or Pioneer 13 was a spacecraft launched in 1978 to explore Venus as part of NASAs Pioneer program. The Pioneer Venus Multiprobe bus was constructed by the Hughes Aircraft Company and it was cylindrical in shape, with a diameter of 2.5 metres and a mass of 290 kilograms. Unlike the probes, which did not begin making direct measurements until they had decelerated lower in the atmosphere, the bus was targeted to enter the Venusian atmosphere at a shallow entry angle and transmit data until destruction by the heat of atmospheric friction. The spacecraft carried one large and three small probes, designed to collect data as they descended into the atmosphere of Venus. All four probes continued transmitting data until impact, however, one survived and continued to transmit data from the surface, the Large probe carried seven experiments, contained within a sealed spherical pressure vessel. After deceleration from initial atmospheric entry at about 11.5 kilometres per second near the equator on the side of Venus. The large probe was about 150 centimetres in diameter and the vessel itself was 73.2 centimeters in diameter. Three identical small probes, around 0.8 metres in diameter, were deployed and these probes consisted of spherical pressure vessels surrounded by an aeroshell, but unlike the large probe, they had no parachutes and the aeroshells did not separate from the probes. The small probes were each targeted at different parts of the planet and were named accordingly, the North probe entered the atmosphere at about 60 degrees north latitude on the day side. The Night probe entered on the night side, the Day probe entered well into the day side, and was the only one of the four probes which continued to send radio signals back after impact, for over an hour. The Pioneer Venus Multiprobe was launched by an Atlas SLV-3D Centaur-D1AR rocket, the launch occurred at 07,33 on August 8,1978, and deployed the Multiprobe into heliocentric orbit for its coast to Venus. Prior to the Multiprobe reaching Venus, the four probes were deployed from the main bus, the large probe was released on November 16,1978, and the three small probes on November 20. All four probes and the bus reached Venus on December 9,1978, the large probe was the first to enter the atmosphere, at 18,45,32 UTC, followed over the next 11 minutes by the other three probes. The bus entered the atmosphere at 20,21,52 UTC, the four probes transmitted data until they impacted the surface of Venus. The Day Probe survived impact, returning data from the surface for over an hour, below the altitude of 50 km the temperatures measured by the four probes are identical to within a few degrees. They are between 448 °C and 459 °C on the surface, the ground pressure is between 86.2 bar and 94.5 bar. Nephelometers identified three cloud layers with different characteristics, overall data from airborne sensors confirmed, while specifying the data obtained by the Soviet space probe Venera program that preceded this mission. Young, Richard E. Sommer, Simon C, findlay, John T. Kelly, G. M
18.
Heliocentric orbit
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A heliocentric orbit is an orbit around the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. All planets, comets, and asteroids in the Solar System are in such orbits, the moons of planets in the Solar System, by contrast, are not in heliocentric orbits as they orbit their respective planet. A similar phenomenon allows the detection of exoplanets by way of the radial velocity method, the helio- prefix is derived from the Greek word helios, meaning sun, and also Helios, the personification of the Sun in Greek mythology. The first spacecraft to be put in an orbit is Luna 1. A trans-Mars injection is an orbit in which a propulsive maneuver is used to set a spacecraft on a trajectory, also known as Mars transfer orbit. Every two years, low-energy transfer windows open up which allow movement between planets with the lowest possible delta-v requirements, transfer injections can place spacecraft into either a Hohmann transfer orbit or bi-elliptic transfer orbit. Trans-Mars injections can be either a single maneuver burn, such as used by the NASA MAVEN orbiter, or a series of perigee kicks. Earths orbit Geocentric orbit Heliocentrism Astrodynamics Low-energy transfer List of artificial objects in heliocentric orbit List of orbits
19.
Kennedy Space Center
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The John F. Kennedy Space Center is one of ten National Aeronautics and Space Administration field centers. Since December 1968, Kennedy Space Center has been NASAs primary launch center of human spaceflight, Launch operations for the Apollo, Skylab and Space Shuttle programs were carried out from Kennedy Space Center Launch Complex 39 and managed by KSC. Located on the east coast of Florida, KSC is adjacent to Cape Canaveral Air Force Station, the management of the two entities work very closely together, share resources, and even own facilities on each others property. Additionally, the center manages launch of robotic and commercial missions, researches food production and In-Situ Resource Utilization for off Earth exploration. Since 2010, the center has worked to become a multi-user spaceport through industry partnerships, there are about 700 facilities grouped across the centers 144,000 acres. There is also a Visitor Complex open to the public on site, the military had been performing launch operations since 1949 at what would become Cape Canaveral Air Force Station. In December 1959, the Department of Defense transferred 5,000 personnel, President John F. Kennedys 1961 goal of a manned lunar landing before 1970 required an expansion of launch operations. On July 1,1962, the Launch Operations Directorate was separated from MSFC to become the Launch Operations Center, therefore, the decision was made to build a new LOC site located adjacent to Cape Canaveral on Merritt Island. NASA began land acquisition in 1962, buying title to 131 square miles, the major buildings in KSCs Industrial Area were designed by architect Charles Luckman. Construction began in November 1962, and Kennedy visited the site twice in 1962, on November 29,1963, the facility was given its current name by President Lyndon B. Johnson under Executive Order 11129. Johnsons order joined both the civilian LOC and the military Cape Canaveral station under the designation John F. Kennedy Space Center, spawning some confusion joining the two in the public mind. Located on Merritt Island, Florida, the center is north-northwest of Cape Canaveral on the Atlantic Ocean and it is 34 miles long and roughly six miles wide, covering 219 square miles. KSC is a major central Florida tourist destination and is one hours drive from the Orlando area. The Kennedy Space Center Visitor Complex offers public tours of the center, Center workers can encounter bald eagles, American alligators, wild boars, eastern diamondback rattlesnakes, the endangered Florida panther and Florida manatees. From 1967 through 1973, there were 13 Saturn V launches, the first of two unmanned flights, Apollo 4 on November 9,1967, was also the first rocket launch from KSC. The Saturn Vs first manned launch on December 21,1968 was Apollo 8s lunar orbiting mission, the next two missions tested the Lunar Module, Apollo 9 and Apollo 10. Apollo 11, launched from Pad A on July 16,1969, Apollo 12 followed four months later. From 1970–1972, the Apollo program concluded at KSC with the launches of missions 13 through 17, on May 14,1973, the last Saturn V launch put the Skylab space station in orbit from Pad 39A
20.
Magnetometer
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A compass is a simple example of a magnetometer, one that measures the direction of an ambient magnetic field. Magnetometers are widely used for measuring the Earths magnetic field and in geophysical surveys to detect anomalies of various types. They are also used in the military to detect submarines, consequently, some countries, such as the United States, Canada and Australia, classify the more sensitive magnetometers as military technology, and control their distribution. Magnetic fields are vector quantities characterized by strength and direction. The strength of a field is measured in units of tesla in the SI units. 10,000 gauss are equal to one tesla, measurements of the Earths magnetic field are often quoted in units of nanotesla, also called a gamma. Gaussmeters and teslameters are magnetometers that measure in units of gauss or tesla, in some contexts, magnetometer is the term used for an instrument that measures fields of less than 1 millitesla and gaussmeter is used for those measuring greater than 1 mT. There are two types of magnetometer measurement. Vector magnetometers measure the components of a magnetic field. Total field magnetometers or scalar magnetometers measure the magnitude of the magnetic field. Magnetometers used to study the Earths magnetic field may express the components of the field in terms of declination. Absolute magnetometers measure the magnitude or vector magnetic field, using an internal calibration or known physical constants of the magnetic sensor. Relative magnetometers measure magnitude or vector magnetic field relative to a fixed but uncalibrated baseline, also called variometers, relative magnetometers are used to measure variations in magnetic field. Magnetometers may also be classified by their situation or intended use, stationary magnetometers are installed to a fixed position and measurements are taken while the magnetometer is stationary. Portable or mobile magnetometers are meant to be used while in motion, laboratory magnetometers are used to measure the magnetic field of materials placed within them and are typically stationary. The performance and capabilities of magnetometers are described through their technical specifications, major specifications include Sample rate is the amount of readings given per second. The inverse is the time in seconds per reading. Sample rate is important in mobile magnetometers, the sample rate, bandwidth or bandpass characterizes how well a magnetometer tracks rapid changes in magnetic field
21.
Solar panel
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Solar panel refers to a panel designed to absorb the suns rays as a source of energy for generating electricity or heating. A photovoltaic module is a packaged, connect assembly of typically 6×10 photovoltaic solar cells, photovoltaic modules constitute the photovoltaic array of a photovoltaic system that generates and supplies solar electricity in commercial and residential applications. Each module is rated by its DC output power under standard test conditions, the efficiency of a module determines the area of a module given the same rated output – an 8% efficient 230 watt module will have twice the area of a 16% efficient 230 watt module. There are a few commercially available solar modules that exceed 22% efficiency, a single solar module can produce only a limited amount of power, most installations contain multiple modules. A photovoltaic system typically includes an array of photovoltaic modules, an inverter, a pack for storage, interconnection wiring. The most common application of solar panels is solar heating systems. The price of power has continued to fall so that in many countries it is cheaper than ordinary fossil fuel electricity from the grid. Photovoltaic modules use light energy from the Sun to generate electricity through the photovoltaic effect, the majority of modules use wafer-based crystalline silicon cells or thin-film cells. The structural member of a module can either be the top layer or the back layer, cells must also be protected from mechanical damage and moisture. Most modules are rigid, but semi-flexible ones are available, based on thin-film cells, the cells must be connected electrically in series, one to another. Externally, most of photovoltaic modules use MC4 connectors type to facilitate easy connections to the rest of the system. Modules electrical connections are made in series to achieve an output voltage and/or in parallel to provide a desired current capability. The conducting wires that take the current off the modules may contain silver, copper or other non-magnetic conductive transition metals, bypass diodes may be incorporated or used externally, in case of partial module shading, to maximize the output of module sections still illuminated. Some special solar PV modules include concentrators in which light is focused by lenses or mirrors onto smaller cells and this enables the use of cells with a high cost per unit area in a cost-effective way. Depending on construction, photovoltaic modules can produce electricity from a range of frequencies of light, hence, much of the incident sunlight energy is wasted by solar modules, and they can give far higher efficiencies if illuminated with monochromatic light. Therefore, another design concept is to split the light into different wavelength ranges and this has been projected to be capable of raising efficiency by 50%. Scientists from Spectrolab, a subsidiary of Boeing, have reported development of solar cells with an efficiency of more than 40%. Currently the best achieved sunlight conversion rate is around 21. 5% in new products typically lower than the efficiencies of their cells in isolation
22.
Antenna (radio)
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In radio and electronics, an antenna, or aerial, is an electrical device which converts electric power into radio waves, and vice versa. It is usually used with a transmitter or radio receiver. In reception, an antenna intercepts some of the power of a wave in order to produce a tiny voltage at its terminals. Antennas are essential components of all equipment that uses radio, typically an antenna consists of an arrangement of metallic conductors, electrically connected to the receiver or transmitter. These time-varying fields radiate away from the antenna into space as a transverse electromagnetic field wave. Antennas can be designed to transmit and receive radio waves in all directions equally. The first antennas were built in 1888 by German physicist Heinrich Hertz in his experiments to prove the existence of electromagnetic waves predicted by the theory of James Clerk Maxwell. Hertz placed dipole antennas at the point of parabolic reflectors for both transmitting and receiving. He published his work in Annalen der Physik und Chemie, the words antenna and aerial are used interchangeably. Occasionally the term aerial is used to mean a wire antenna, however, note the important international technical journal, the IEEE Transactions on Antennas and Propagation. In the United Kingdom and other areas where British English is used, the origin of the word antenna relative to wireless apparatus is attributed to Italian radio pioneer Guglielmo Marconi. In the summer of 1895, Marconi began testing his wireless system outdoors on his fathers estate near Bologna, Marconi discovered that by raising the aerial wire above the ground and connecting the other side of his transmitter to ground, the transmission range was increased. Soon he was able to transmit signals over a hill, a distance of approximately 2.4 kilometres, in Italian a tent pole is known as lantenna centrale, and the pole with the wire was simply called lantenna. Until then wireless radiating transmitting and receiving elements were simply as aerials or terminals. Because of his prominence, Marconis use of the word spread among wireless researchers. In common usage, the antenna may refer broadly to an entire assembly including support structure, enclosure. Especially at microwave frequencies, an antenna may include not only the actual electrical antenna. An antenna, in converting radio waves to electrical signals or vice versa, is a form of transducer, Antennas are required by any radio receiver or transmitter to couple its electrical connection to the electromagnetic field
23.
X band
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The X band is a segment of the microwave radio region of the electromagnetic spectrum. In some cases, such as in engineering, the frequency range of the X band is rather indefinitely set at approximately 7.0 to 11.2 GHz. In radar engineering, the range is specified by the IEEE at 8.0 to 12.0 GHz. This is also the case pertaining to X band military communications satellites, X band is used in radar applications including continuous-wave, pulsed, single-polarization, dual-polarization, synthetic aperture radar, and phased arrays. X band is used in modern radars. The shorter wavelengths of the X band allow for higher resolution imagery from high-resolution imaging radars for target identification and discrimination, in Ireland, Libya, Saudi Arabia and Canada, the X band 10.15 to 10.7 segment is used for terrestrial broadband. Alvarion, CBNL, and Ogier make systems for this, though each has a proprietary airlink, the Ogier system is a full duplex Transverter used for DOCSIS over microwave. The home / Business CPE has a coaxial cable with a power adapter connecting to an ordinary cable modem. The local oscillator is usually 9750 MHz, the same as for Ku band satellite TV LNB, two way applications such as broadband typically use a 350 MHz TX offset. Portions of the X band are assigned by the International Telecommunications Union exclusively for deep space telecommunications, the primary user of this allocation is the American NASA Deep Space Network. DSN facilities are located in Goldstone, California, near Canberra, Australia and these three stations, located approximately 120 degrees apart in longitude, provide continual communications from the Earth to almost any point in the Solar System independent of Earth rotation. DSN stations are capable of using the older and lower S band deep-space radio communications allocations and it will also detect variations in angular momentum due to the redistribution of masses, such as the migration of ice from the polar caps to the atmosphere. An important use of the X band communications came with the two Viking program landers and these results are some of the best confirmations of the General Theory of Relativity. This is known as the 3-centimeter band by amateurs and the X-band by AMSAT, motion detectors often use 10.525 GHz.10.4 GHz is proposed for traffic light crossing detectors. Comreg in Ireland has allocated 10.450 GHz for Traffic Sensors as SRD, many electron paramagnetic resonance spectrometers operate near 9.8 GHz. Particle accelerators may be powered by X-band RF sources, the frequencies are then standardized at 11.9942 GHz or 11.424 GHz, which is the second harmonic of C-band and fourth harmonic of S-band. The European X-band frequency is used for the Compact Linear Collider. ntia. doc. gov/osmhome/allochrt. pdf http, //www. g3pho. free-online. co. uk/microwaves/wideband. htm
24.
Earth
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Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, thus, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, politically, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe. It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, originally, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun
25.
Solid-propellant rocket
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A solid-propellant rocket or solid rocket is a rocket with a rocket engine that uses solid propellants. The earliest rockets were solid-fuel rockets powered by gunpowder, they were used in warfare by the Chinese, Indians, Mongols and Persians, all rockets used some form of solid or powdered propellant up until the 20th century, when liquid-propellant rockets offered more efficient and controllable alternatives. Solid rockets are used today in model rockets and on larger applications for their simplicity and reliability. Since solid-fuel rockets can remain in storage for periods, and then reliably launch on short notice. Solids are, however, frequently used as boosters to increase payload capacity or as spin-stabilized add-on upper stages when higher-than-normal velocities are required. Solid rockets are used as launch vehicles for low Earth orbit payloads under 2 tons or escape payloads up to 500 kilograms. A simple solid rocket motor consists of a casing, nozzle, grain, the grain behaves like a solid mass, burning in a predictable fashion and producing exhaust gases. The nozzle dimensions are calculated to maintain a design chamber pressure, once ignited, a simple solid rocket motor cannot be shut off, because it contains all the ingredients necessary for combustion within the chamber in which they are burned. More advanced solid rocket motors can not only be throttled but also be extinguished, also, pulsed rocket motors that burn in segments and that can be ignited upon command are available. Design begins with the total impulse required, which determines the fuel/oxidizer mass, grain geometry and chemistry are then chosen to satisfy the required motor characteristics. The following are chosen or solved simultaneously, the results are exact dimensions for grain, nozzle, and case geometries, The grain burns at a predictable rate, given its surface area and chamber pressure. The chamber pressure is determined by the orifice diameter and grain burn rate. Allowable chamber pressure is a function of casing design, the length of burn time is determined by the grain web thickness. The grain may or may not be bonded to the casing, case-bonded motors are more difficult to design, since the deformation of the case and the grain under flight must be compatible. Common modes of failure in rocket motors include fracture of the grain, failure of case bonding. All of these produce an increase in burn surface area and a corresponding increase in exhaust gas production rate and pressure. Another failure mode is casing seal failure, seals are required in casings that have to be opened to load the grain. Once a seal fails, hot gas will erode the escape path and this was the cause of the Space Shuttle Challenger disaster
26.
Magellan (spacecraft)
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Magellan was the fifth successful NASA mission to Venus, and it ended an eleven-year gap in U. S. interplanetary probe launches. Beginning in the late 1970s, scientists pushed for a mapping mission to Venus. They first sought to construct a spacecraft named the Venus Orbiting Imaging Radar, the VOIR mission was canceled in 1982. A simplified radar mission proposal was recommended by the Solar System Exploration Committee, the proposal included a limited focus and a single primary scientific instrument. In 1985, the mission was renamed Magellan, in honor of the sixteenth-century Portuguese explorer Ferdinand Magellan, known for his exploration, mapping, and circumnavigation of the Earth. The objectives of the included, Obtain near-global radar images of the Venusian surface with a resolution equivalent to optical imaging of 1.0 km per line pair. Obtain a near-global topographic map with 50 km spatial and 100 m vertical resolution, Obtain near-global gravity field data with 700 km resolution and two to three milligals of accuracy. Develop an understanding of the structure of the planet, including its density distribution. The spacecraft was designed and built by the Martin Marietta Company, elizabeth Beyer served as the program manager and Joseph Boyce served as the lead program scientist for the NASA headquarters. For JPL, Douglas Griffith served as the Magellan project manager, to save costs, most of the Magellan probe was made up of spare parts from various missions, including the Voyager program, Galileo, Ulysses, and Mariner 9. The main body of the spacecraft, a spare one from the Voyager missions, was a 10-sided aluminum bus, containing the computers, data recorders, the spacecraft measured 6.4 meters tall and 4.6 meters in diameter. Overall, the spacecraft weighed 1,035 kilograms and carried 2,414 kilograms of propellant for a mass of 3,449 kilograms. The spacecraft was designed to be stabilized, including during the firing of the Star 48B solid rocket motor used to place it into orbit around Venus. Prior to Magellan, all spacecraft SRM firings had involved spinning spacecraft, in a typical spin mode, any unwanted forces related to SRM or nozzle mis-alignments are cancelled out. The Star 48B, containing 2,014 kg of propellant, developed a thrust of ~89,000 Newton shortly after firing, therefore. The actual propulsion system consisted of a total of 24 monopropellant hydrazine thrusters fed from a single 71 cm diameter titanium tank. The tank contained 133 kg of purified hydrazine, other hardware regarding orientation of the spacecraft consists of a set of gyroscopes and a star scanner. For communications, the spacecraft included a lightweight graphite/aluminum,3. 7-meter high-gain antenna left over from the Voyager Program, a low-gain antenna attached to the high-gain antenna, was also included for contingencies
27.
Atmospheric entry
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Atmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet or natural satellite. Technologies and procedures allowing the atmospheric entry, descent and landing of spacecraft are collectively abbreviated as EDL. Atmospheric drag and aerodynamic heating can cause atmospheric breakup capable of completely disintegrating smaller objects and these forces may cause objects with lower compressive strength to explode. Manned space vehicles must be slowed to subsonic speeds before parachutes or air brakes may be deployed, such vehicles have kinetic energies typically between 50 and 1800 MJoules, and atmospheric dissipation is the only way of expending the kinetic energy. While the high temperature generated at the surface of the shield is due to adiabatic compression. Other smaller energy losses include black body radiation directly from the hot gasses, ballistic warheads and expendable vehicles do not require slowing at re-entry, and in fact, are made streamlined so as to maintain their speed. Uncontrolled, objects accelerate through the atmosphere at extreme velocities under the influence of Earths gravity, most controlled objects enter at hypersonic speeds due to their suborbital, orbital, or unbounded trajectories. Various advanced technologies have developed to enable atmospheric reentry and flight at extreme velocities. Practical development of systems began as the range and reentry velocity of ballistic missiles increased. For early short-range missiles, like the V-2, stabilization and aerodynamic stress were important issues, medium-range missiles like the Soviet R-5, with a 1200 km range, required ceramic composite heat shielding on separable reentry vehicles. The first ICBMs, with ranges of 8000 to 12,000 km, were possible with the development of modern ablative heat shields. In the U. S. this technology was pioneered by H. Julian Allen at Ames Research Center, over the decades since the 1950s, a rich technical jargon has grown around the engineering of vehicles designed to enter planetary atmospheres. It is recommended that the review the jargon glossary before continuing with this article on atmospheric reentry. When atmospheric entry is part of a landing or recovery, particularly on a planetary body other than Earth, entry is part of a phase referred to as entry, descent and landing. When the atmospheric entry returns to the body that the vehicle had launched from. These four shadowgraph images represent early reentry-vehicle concepts, if the reentry vehicle is made blunt, air cannot get out of the way quickly enough, and acts as an air cushion to push the shock wave and heated shock layer forward. Since most of the hot gases are no longer in contact with the vehicle. The Allen and Eggers discovery, though initially treated as a secret, was eventually published in 1958
28.
Atmosphere of Venus
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The atmosphere of Venus is the layer of gases surrounding Venus. It is composed primarily of carbon dioxide and is denser and hotter than that of Earth. The temperature at the surface is 740 K, and the pressure is 93 bar, the Venusian atmosphere supports opaque clouds made of sulfuric acid, making optical Earth-based and orbital observation of the surface impossible. Information about the topography has been obtained exclusively by radar imaging, aside from carbon dioxide, the other main component is nitrogen. Other chemical compounds are present only in trace amounts, aside from the very surface layers, the atmosphere is in a state of vigorous circulation. The upper layer of troposphere exhibits a phenomenon of super-rotation, in which the circles the planet in just four Earth days. The winds supporting super-rotation blow as fast as 100 m/s, winds move at up to 60 times the speed of the planets rotation, while Earths fastest winds are only 10% to 20% rotation speed. On the other hand, the wind speed becomes increasingly slower as the elevation from the surface decreases, near the poles are anticyclonic structures called polar vortices. Each vortex is double-eyed and shows a characteristic S-shaped pattern of clouds, above there is an intermediate layer of mesosphere which separates the troposphere from the thermosphere. Unlike Earth, Venus lacks a magnetic field and its ionosphere separates the atmosphere from outer space and the solar wind. This ionised layer excludes the solar field, giving Venus a distinct magnetic environment. This is considered Venuss induced magnetosphere, lighter gases, including water vapour, are continuously blown away by the solar wind through the induced magnetotail. It is speculated that the atmosphere of Venus up to around 4 billion years ago was more like that of the Earth with liquid water on the surface. A runaway greenhouse effect may have been caused by the evaporation of the surface water, on January 29,2013, ESA scientists reported that the ionosphere of the planet Venus streams outwards in a manner similar to the ion tail seen streaming from a comet under similar conditions. The atmosphere of Venus is composed of 96. 5% carbon dioxide,3. 5% nitrogen, the atmosphere contains a range of interesting compounds in small quantities, including some based on hydrogen, such as hydrogen chloride and hydrogen fluoride. There is carbon monoxide, water vapour and atomic oxygen as well, hydrogen is in relatively short supply in the Venusian atmosphere. A large amount of the hydrogen is theorised to have been lost to space, with the remainder being mostly bound up in sulfuric acid. The loss of significant amounts of hydrogen is proved by a very high D–H ratio measured in the Venusian atmosphere, the ratio is about 0. 015–0.025, which is 100–150 times higher than the terrestrial value of 1. 6×10−4
29.
Pioneer 10
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Pioneer 10 is an American space probe, launched in 1972 and weighing 258 kilograms, that completed the first mission to the planet Jupiter. Thereafter, Pioneer 10 became the first spacecraft to escape velocity from the Solar System. This space exploration project was conducted by the NASA Ames Research Center in California, Pioneer 10 was assembled around a hexagonal bus with a 2.74 meters diameter parabolic dish high-gain antenna, and the spacecraft was spin stabilized around the axis of the antenna. Its electric power was supplied by four radioisotope thermoelectric generators that provided a combined 155 watts at launch and it was launched on March 2,1972, by an Atlas-Centaur expendable vehicle from Cape Canaveral, Florida. Between July 15,1972, and February 15,1973, photography of Jupiter began November 6,1973, at a range of 25,000,000 kilometers, and a total of about 500 images were transmitted. The closest approach to the planet was on December 4,1973, radio communications were lost with Pioneer 10 on January 23,2003, because of the loss of electric power for its radio transmitter, with the probe at a distance of 12 billion kilometers from Earth. An advocacy group named the Outer Space Panel and chaired by American space scientist James A. Van Allen, NASA Goddard Spaceflight Center put together a proposal for a pair of Galactic Jupiter Probes that would pass through the asteroid belt and visit Jupiter. These were to be launched in 1972 and 1973 during favorable windows that occurred only a few weeks every 13 months, Launch during other time intervals would have been more costly in terms of propellant requirements. Approved by NASA in February 1969, the spacecraft were designated Pioneer F and Pioneer G before launch, later they were named Pioneer 10. They formed part of the Pioneer program, a series of United States unmanned space missions launched between 1958 and 1978 and this model was the first in the series to be designed for exploring the outer Solar System. More than 150 scientific experiments were proposed for the missions, the experiments to be carried on the spacecraft were selected in a series of planning sessions during the 1960s, then were finalized by early 1970. NASA Ames Research Center, rather than Goddard, was selected to manage the project as part of the Pioneer program, the Ames Research Center, under the direction of Charles F. Hall, was chosen because of its previous experience with spin-stabilized spacecraft. The requirements called for a small, lightweight spacecraft which was magnetically clean and it was to use spacecraft modules that had already been proven in the Pioneer 6 through 9 missions. In February 1970, Ames awarded a combined $380 million contract to TRW for building both of the Pioneer 10 and 11 vehicles, bypassing the usual bidding process to save time, B. J. OBrien and Herb Lassen led the TRW team that assembled the spacecraft. Design and construction of the spacecraft required an estimated 25 million man-hours, to meet the schedule, the first launch would need to take place between February 29 and March 17 so that it could arrive at Jupiter in November 1974. The encounter trajectory for Pioneer 10 was selected to maximize the information returned about the environment around Jupiter. It would come within three times the radius of the planet, which was thought to be the closest it could approach. The trajectory chosen would give the spacecraft a good view of the sunlit side, the Pioneer 10 bus measured 36 centimeters deep and with six 76-centimeter long panels forming the hexagonal structure
30.
Hertz
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The hertz is the unit of frequency in the International System of Units and is defined as one cycle per second. It is named for Heinrich Rudolf Hertz, the first person to provide proof of the existence of electromagnetic waves. Hertz are commonly expressed in SI multiples kilohertz, megahertz, gigahertz, kilo means thousand, mega meaning million, giga meaning billion and tera for trillion. Some of the units most common uses are in the description of waves and musical tones, particularly those used in radio-. It is also used to describe the speeds at which computers, the hertz is equivalent to cycles per second, i. e. 1/second or s −1. In English, hertz is also used as the plural form, as an SI unit, Hz can be prefixed, commonly used multiples are kHz, MHz, GHz and THz. One hertz simply means one cycle per second,100 Hz means one hundred cycles per second, and so on. The unit may be applied to any periodic event—for example, a clock might be said to tick at 1 Hz, the rate of aperiodic or stochastic events occur is expressed in reciprocal second or inverse second in general or, the specific case of radioactive decay, becquerels. Whereas 1 Hz is 1 cycle per second,1 Bq is 1 aperiodic radionuclide event per second, the conversion between a frequency f measured in hertz and an angular velocity ω measured in radians per second is ω =2 π f and f = ω2 π. This SI unit is named after Heinrich Hertz, as with every International System of Units unit named for a person, the first letter of its symbol is upper case. Note that degree Celsius conforms to this rule because the d is lowercase. — Based on The International System of Units, the hertz is named after the German physicist Heinrich Hertz, who made important scientific contributions to the study of electromagnetism. The name was established by the International Electrotechnical Commission in 1930, the term cycles per second was largely replaced by hertz by the 1970s. One hobby magazine, Electronics Illustrated, declared their intention to stick with the traditional kc. Mc. etc. units, sound is a traveling longitudinal wave which is an oscillation of pressure. Humans perceive frequency of waves as pitch. Each musical note corresponds to a frequency which can be measured in hertz. An infants ear is able to perceive frequencies ranging from 20 Hz to 20,000 Hz, the range of ultrasound, infrasound and other physical vibrations such as molecular and atomic vibrations extends from a few femtoHz into the terahertz range and beyond. Electromagnetic radiation is described by its frequency—the number of oscillations of the perpendicular electric and magnetic fields per second—expressed in hertz. Radio frequency radiation is measured in kilohertz, megahertz, or gigahertz
31.
Infrared
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It extends from the nominal red edge of the visible spectrum at 700 nanometers, to 1000000 nm. Most of the radiation emitted by objects near room temperature is infrared. Like all EMR, IR carries radiant energy, and behaves both like a wave and like its quantum particle, the photon, slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has an effect on Earths climate. Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements and it excites vibrational modes in a molecule through a change in the dipole moment, making it a useful frequency range for study of these energy states for molecules of the proper symmetry. Infrared spectroscopy examines absorption and transmission of photons in the infrared range, Infrared radiation is used in industrial, scientific, and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected, Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, and to detect overheating of electrical apparatuses. Thermal-infrared imaging is used extensively for military and civilian purposes, military applications include target acquisition, surveillance, night vision, homing, and tracking. Humans at normal body temperature radiate chiefly at wavelengths around 10 μm, Infrared radiation extends from the nominal red edge of the visible spectrum at 700 nanometers to 1 mm. This range of wavelengths corresponds to a range of approximately 430 THz down to 300 GHz. Below infrared is the portion of the electromagnetic spectrum. Sunlight, at a temperature of 5,780 kelvins, is composed of near thermal-spectrum radiation that is slightly more than half infrared. At zenith, sunlight provides an irradiance of just over 1 kilowatt per square meter at sea level, of this energy,527 watts is infrared radiation,445 watts is visible light, and 32 watts is ultraviolet radiation. Nearly all the radiation in sunlight is near infrared, shorter than 4 micrometers. On the surface of Earth, at far lower temperatures than the surface of the Sun, almost all thermal radiation consists of infrared in mid-infrared region, much longer than in sunlight. Of these natural thermal radiation processes only lightning and natural fires are hot enough to produce much visible energy, thermal infrared radiation also has a maximum emission wavelength, which is inversely proportional to the absolute temperature of object, in accordance with Wiens displacement law. Therefore, the band is often subdivided into smaller sections. Due to the nature of the blackbody radiation curves, typical hot objects, such as exhaust pipes, the three regions are used for observation of different temperature ranges, and hence different environments in space
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Ultraviolet
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Ultraviolet is an electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation constitutes about 10% of the light output of the Sun. It is also produced by electric arcs and specialized lights, such as lamps, tanning lamps. Consequently, the effects of UV are greater than simple heating effects. Suntan, freckling and sunburn are familiar effects of over-exposure, along with risk of skin cancer. Living things on dry land would be damaged by ultraviolet radiation from the Sun if most of it were not filtered out by the Earths atmosphere. More-energetic, shorter-wavelength extreme UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground, Ultraviolet is also responsible for the formation of bone-strengthening vitamin D in most land vertebrates, including humans. The UV spectrum thus has both beneficial and harmful to human health. Ultraviolet rays are invisible to most humans, the lens in a human eye ordinarily filters out UVB frequencies or higher, and humans lack color receptor adaptations for ultraviolet rays. Under some conditions, children and young adults can see ultraviolet down to wavelengths of about 310 nm, near-UV radiation is visible to some insects, mammals, and birds. Small birds have a fourth color receptor for ultraviolet rays, this gives birds true UV vision, reindeer use near-UV radiation to see polar bears, who are poorly visible in regular light because they blend in with the snow. UV also allows mammals to see urine trails, which is helpful for animals to find food in the wild. The males and females of some species look identical to the human eye. Ultraviolet means beyond violet, violet being the color of the highest frequencies of visible light, Ultraviolet has a higher frequency than violet light. He called them oxidizing rays to emphasize chemical reactivity and to them from heat rays. The terms chemical and heat rays were eventually dropped in favour of ultraviolet and infrared radiation, in 1878 the effect of short-wavelength light on sterilizing bacteria was discovered. By 1903 it was known the most effective wavelengths were around 250 nm, in 1960, the effect of ultraviolet radiation on DNA was established. The discovery of the ultraviolet radiation below 200 nm, named vacuum ultraviolet because it is absorbed by air, was made in 1893 by the German physicist Victor Schumann
33.
Mass spectrometry
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Mass spectrometry is an analytical technique that ionizes chemical species and sorts the ions based on their mass-to-charge ratio. In simpler terms, a mass spectrum measures the masses within a sample, mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures. A mass spectrum is a plot of the ion signal as a function of the mass-to-charge ratio, in a typical MS procedure, a sample, which may be solid, liquid, or gas, is ionized, for example by bombarding it with electrons. This may cause some of the molecules to break into charged fragments. The ions are detected by a capable of detecting charged particles. Results are displayed as spectra of the abundance of detected ions as a function of the mass-to-charge ratio. The atoms or molecules in the sample can be identified by correlating known masses to the masses or through a characteristic fragmentation pattern. Goldstein called these positively charged anode rays Kanalstrahlen, the translation of this term into English is canal rays. Wien found that the charge-to-mass ratio depended on the nature of the gas in the discharge tube, thomson later improved on the work of Wien by reducing the pressure to create the mass spectrograph. The word spectrograph had become part of the international scientific vocabulary by 1884, a mass spectroscope is similar to a mass spectrograph except that the beam of ions is directed onto a phosphor screen. A mass spectroscope configuration was used in early instruments when it was desired that the effects of adjustments be quickly observed, once the instrument was properly adjusted, a photographic plate was inserted and exposed. The term mass spectroscope continued to be used though the direct illumination of a phosphor screen was replaced by indirect measurements with an oscilloscope. The use of the mass spectroscopy is now discouraged due to the possibility of confusion with light spectroscopy. Mass spectrometry is often abbreviated as mass-spec or simply as MS, modern techniques of mass spectrometry were devised by Arthur Jeffrey Dempster and F. W. Aston in 1918 and 1919 respectively. Sector mass spectrometers known as calutrons were used for separating the isotopes of uranium developed by Ernest O. Lawrence during the Manhattan Project, calutron mass spectrometers were used for uranium enrichment at the Oak Ridge, Tennessee Y-12 plant established during World War II. In 1989, half of the Nobel Prize in Physics was awarded to Hans Dehmelt, a mass spectrometer consists of three components, an ion source, a mass analyzer, and a detector. The ionizer converts a portion of the sample into ions, there is a wide variety of ionization techniques, depending on the phase of the sample and the efficiency of various ionization mechanisms for the unknown species. An extraction system removes ions from the sample, which are then targeted through the mass analyzer, the differences in masses of the fragments allows the mass analyzer to sort the ions by their mass-to-charge ratio
34.
Solar wind
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The solar wind is a stream of charged particles released from the upper atmosphere of the Sun. This plasma consists of electrons, protons and alpha particles with thermal energies between 1.5 and 10 keV. Embedded within the plasma is the interplanetary magnetic field. The solar wind varies in density, temperature and speed over time and its particles can escape the Suns gravity because of their high energy resulting from the high temperature of the corona, which in turn is a result of the coronal magnetic field. At a distance of more than a few radii from the sun. The flow of the wind is no longer supersonic at the termination shock. The Voyager 2 spacecraft crossed the shock more than five times between 30 August and 10 December 2007, Voyager 2 crossed the shock about a billion kilometers closer to the Sun than the 13.5 billion kilometer distance where Voyager 1 came upon the termination shock. The spacecraft moved outward through the shock into the heliosheath. Other related phenomena include the aurora, the tails of comets that always point away from the Sun. The existence of flowing outward from the Sun to the Earth was first suggested by British astronomer Richard C. In 1859, Carrington and Richard Hodgson independently made the first observation of what would later be called a solar flare, george FitzGerald later suggested that matter was being regularly accelerated away from the Sun and was reaching the Earth after several days. In 1910 British astrophysicist Arthur Eddington essentially suggested the existence of the wind, without naming it. The idea never caught on even though Eddington had also made a similar suggestion at a Royal Institution address the previous year. In the latter case, he postulated that the material consisted of electrons while in his study of Comet Morehouse he supposed them to be ions. The first person to suggest that the material consisted of both ions and electrons was Kristian Birkeland. His geomagnetic surveys showed that activity was nearly uninterrupted. In 1916, Birkeland proposed that, From a physical point of view it is most probable that solar rays are neither exclusively negative nor positive rays, in other words, the solar wind consists of both negative electrons and positive ions. Three years later in 1919, Frederick Lindemann also suggested that particles of both polarities, protons as well as electrons, come from the Sun
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Plasma (physics)
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Plasma is one of the four fundamental states of matter, the others being solid, liquid, and gas. Yet unlike these three states of matter, plasma does not naturally exist on the Earth under normal surface conditions, the term was first introduced by chemist Irving Langmuir in the 1920s. However, true plasma production is from the separation of these ions and electrons that produces an electric field. Based on the environmental temperature and density either partially ionised or fully ionised forms of plasma may be produced. The positive charge in ions is achieved by stripping away electrons from atomic nuclei, the number of electrons removed is related to either the increase in temperature or the local density of other ionised matter. Plasma may be the most abundant form of matter in the universe, although this is currently tentative based on the existence. Plasma is mostly associated with the Sun and stars, extending to the rarefied intracluster medium, Plasma was first identified in a Crookes tube, and so described by Sir William Crookes in 1879. The nature of the Crookes tube cathode ray matter was identified by British physicist Sir J. J. The term plasma was coined by Irving Langmuir in 1928, perhaps because the glowing discharge molds itself to the shape of the Crookes tube and we shall use the name plasma to describe this region containing balanced charges of ions and electrons. Plasma is a neutral medium of unbound positive and negative particles. Although these particles are unbound, they are not ‘free’ in the sense of not experiencing forces, in turn this governs collective behavior with many degrees of variation. The average number of particles in the Debye sphere is given by the plasma parameter, bulk interactions, The Debye screening length is short compared to the physical size of the plasma. This criterion means that interactions in the bulk of the plasma are more important than those at its edges, when this criterion is satisfied, the plasma is quasineutral. Plasma frequency, The electron plasma frequency is compared to the electron-neutral collision frequency. When this condition is valid, electrostatic interactions dominate over the processes of ordinary gas kinetics, for plasma to exist, ionization is necessary. The term plasma density by itself refers to the electron density, that is. The degree of ionization of a plasma is the proportion of atoms that have lost or gained electrons, even a partially ionized gas in which as little as 1% of the particles are ionized can have the characteristics of a plasma. The degree of ionization, α, is defined as α = n i n i + n n, where n i is the number density of ions and n n is the number density of neutral atoms
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Magnetic field
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A magnetic field is the magnetic effect of electric currents and magnetic materials. The magnetic field at any point is specified by both a direction and a magnitude, as such it is represented by a vector field. The term is used for two distinct but closely related fields denoted by the symbols B and H, where H is measured in units of amperes per meter in the SI, B is measured in teslas and newtons per meter per ampere in the SI. B is most commonly defined in terms of the Lorentz force it exerts on moving electric charges, Magnetic fields can be produced by moving electric charges and the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property, their spin. In quantum physics, the field is quantized and electromagnetic interactions result from the exchange of photons. Magnetic fields are used throughout modern technology, particularly in electrical engineering. The Earth produces its own field, which is important in navigation. Rotating magnetic fields are used in electric motors and generators. Magnetic forces give information about the carriers in a material through the Hall effect. The interaction of magnetic fields in electric devices such as transformers is studied in the discipline of magnetic circuits, noting that the resulting field lines crossed at two points he named those points poles in analogy to Earths poles. He also clearly articulated the principle that magnets always have both a north and south pole, no matter how finely one slices them, almost three centuries later, William Gilbert of Colchester replicated Petrus Peregrinus work and was the first to state explicitly that Earth is a magnet. Published in 1600, Gilberts work, De Magnete, helped to establish magnetism as a science, in 1750, John Michell stated that magnetic poles attract and repel in accordance with an inverse square law. Charles-Augustin de Coulomb experimentally verified this in 1785 and stated explicitly that the north and south poles cannot be separated, building on this force between poles, Siméon Denis Poisson created the first successful model of the magnetic field, which he presented in 1824. In this model, a magnetic H-field is produced by magnetic poles, three discoveries challenged this foundation of magnetism, though. First, in 1819, Hans Christian Ørsted discovered that an electric current generates a magnetic field encircling it, then in 1820, André-Marie Ampère showed that parallel wires having currents in the same direction attract one another. Finally, Jean-Baptiste Biot and Félix Savart discovered the Biot–Savart law in 1820, extending these experiments, Ampère published his own successful model of magnetism in 1825. This has the benefit of explaining why magnetic charge can not be isolated. Also in this work, Ampère introduced the term electrodynamics to describe the relationship between electricity and magnetism, in 1831, Michael Faraday discovered electromagnetic induction when he found that a changing magnetic field generates an encircling electric field
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Electron
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The electron is a subatomic particle, symbol e− or β−, with a negative elementary electric charge. Electrons belong to the first generation of the lepton particle family, the electron has a mass that is approximately 1/1836 that of the proton. Quantum mechanical properties of the include a intrinsic angular momentum of a half-integer value, expressed in units of the reduced Planck constant. As it is a fermion, no two electrons can occupy the same state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of particles and waves, they can collide with other particles and can be diffracted like light. Since an electron has charge, it has an electric field. Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law, electrons radiate or absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields, special telescopes can detect electron plasma in outer space. Electrons are involved in applications such as electronics, welding, cathode ray tubes, electron microscopes, radiation therapy, lasers, gaseous ionization detectors. Interactions involving electrons with other particles are of interest in fields such as chemistry. The Coulomb force interaction between the positive protons within atomic nuclei and the negative electrons without, allows the composition of the two known as atoms, ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the cause of chemical bonding. In 1838, British natural philosopher Richard Laming first hypothesized the concept of a quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge electron in 1891, electrons can also participate in nuclear reactions, such as nucleosynthesis in stars, where they are known as beta particles. Electrons can be created through beta decay of isotopes and in high-energy collisions. The antiparticle of the electron is called the positron, it is identical to the electron except that it carries electrical, when an electron collides with a positron, both particles can be totally annihilated, producing gamma ray photons. The ancient Greeks noticed that amber attracted small objects when rubbed with fur, along with lightning, this phenomenon is one of humanitys earliest recorded experiences with electricity. In his 1600 treatise De Magnete, the English scientist William Gilbert coined the New Latin term electricus, both electric and electricity are derived from the Latin ēlectrum, which came from the Greek word for amber, ἤλεκτρον
38.
Ionosphere
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The ionosphere is a region of Earths upper atmosphere, from about 60 km to 1,000 km altitude, and includes the thermosphere and parts of the mesosphere and exosphere. It is ionized by radiation, plays an important part in atmospheric electricity. It has practical importance because, among other functions, it influences radio propagation to distant places on the Earth. The ionosphere is a shell of electrons and electrically charged atoms and molecules that surrounds the Earth and it owes its existence primarily to ultraviolet radiation from the Sun. The lowest part of the Earths atmosphere, the troposphere extends from the surface to about 10 km, above 10 km is the stratosphere, followed by the mesosphere. In the stratosphere incoming solar radiation creates the ozone layer, at heights of above 80 km, in the thermosphere, the atmosphere is so thin that free electrons can exist for short periods of time before they are captured by a nearby positive ion. The number of free electrons is sufficient to affect radio propagation. This portion of the atmosphere is ionized and contains a plasma which is referred to as the ionosphere, in this process the light electron obtains a high velocity so that the temperature of the created electronic gas is much higher than the one of ions and neutrals. The reverse process to ionization is recombination, in which an electron is captured by a positive ion. Recombination occurs spontaneously, and causes the emission of a photon carrying away the energy produced upon recombination, as gas density increases at lower altitudes, the recombination process prevails, since the gas molecules and ions are closer together. The balance between two processes determines the quantity of ionization present. Ionization depends primarily on the Sun and its activity, the amount of ionization in the ionosphere varies greatly with the amount of radiation received from the Sun. Thus there is an effect and a seasonal effect. The local winter hemisphere is tipped away from the Sun, thus there is less received solar radiation, the activity of the Sun is associated with the sunspot cycle, with more radiation occurring with more sunspots. Radiation received also varies with geographical location, there are also mechanisms that disturb the ionosphere and decrease the ionization. There are disturbances such as flares and the associated release of charged particles into the solar wind which reaches the Earth. At night the F layer is the layer of significant ionization present. During the day, the D and E layers become more heavily ionized, as does the F layer
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Radio
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When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form, Radio systems need a transmitter to modulate some property of the energy produced to impress a signal on it, for example using amplitude modulation or angle modulation. Radio systems also need an antenna to convert electric currents into radio waves, an antenna can be used for both transmitting and receiving. The electrical resonance of tuned circuits in radios allow individual stations to be selected, the electromagnetic wave is intercepted by a tuned receiving antenna. Radio frequencies occupy the range from a 3 kHz to 300 GHz, a radio communication system sends signals by radio. The term radio is derived from the Latin word radius, meaning spoke of a wheel, beam of light, however, this invention would not be widely adopted. The switch to radio in place of wireless took place slowly and unevenly in the English-speaking world, the United States Navy would also play a role. Although its translation of the 1906 Berlin Convention used the terms wireless telegraph and wireless telegram, the term started to become preferred by the general public in the 1920s with the introduction of broadcasting. Radio systems used for communication have the following elements, with more than 100 years of development, each process is implemented by a wide range of methods, specialised for different communications purposes. Each system contains a transmitter, This consists of a source of electrical energy, the transmitter contains a system to modulate some property of the energy produced to impress a signal on it. This modulation might be as simple as turning the energy on and off, or altering more subtle such as amplitude, frequency, phase. Amplitude modulation of a carrier wave works by varying the strength of the signal in proportion to the information being sent. For example, changes in the strength can be used to reflect the sounds to be reproduced by a speaker. It was the used for the first audio radio transmissions. Frequency modulation varies the frequency of the carrier, the instantaneous frequency of the carrier is directly proportional to the instantaneous value of the input signal. FM has the capture effect whereby a receiver only receives the strongest signal, Digital data can be sent by shifting the carriers frequency among a set of discrete values, a technique known as frequency-shift keying. FM is commonly used at Very high frequency radio frequencies for high-fidelity broadcasts of music, analog TV sound is also broadcast using FM. Angle modulation alters the phase of the carrier wave to transmit a signal
40.
Gravity
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Gravity, or gravitation, is a natural phenomenon by which all things with mass are brought toward one another, including planets, stars and galaxies. Since energy and mass are equivalent, all forms of energy, including light, on Earth, gravity gives weight to physical objects and causes the ocean tides. Gravity has a range, although its effects become increasingly weaker on farther objects. The most extreme example of this curvature of spacetime is a hole, from which nothing can escape once past its event horizon. More gravity results in time dilation, where time lapses more slowly at a lower gravitational potential. Gravity is the weakest of the four fundamental interactions of nature, the gravitational attraction is approximately 1038 times weaker than the strong force,1036 times weaker than the electromagnetic force and 1029 times weaker than the weak force. As a consequence, gravity has an influence on the behavior of subatomic particles. On the other hand, gravity is the dominant interaction at the macroscopic scale, for this reason, in part, pursuit of a theory of everything, the merging of the general theory of relativity and quantum mechanics into quantum gravity, has become an area of research. While the modern European thinkers are credited with development of gravitational theory, some of the earliest descriptions came from early mathematician-astronomers, such as Aryabhata, who had identified the force of gravity to explain why objects do not fall out when the Earth rotates. Later, the works of Brahmagupta referred to the presence of force, described it as an attractive force. Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th and this was a major departure from Aristotles belief that heavier objects have a higher gravitational acceleration. Galileo postulated air resistance as the reason that objects with less mass may fall slower in an atmosphere, galileos work set the stage for the formulation of Newtons theory of gravity. In 1687, English mathematician Sir Isaac Newton published Principia, which hypothesizes the inverse-square law of universal gravitation. Newtons theory enjoyed its greatest success when it was used to predict the existence of Neptune based on motions of Uranus that could not be accounted for by the actions of the other planets. Calculations by both John Couch Adams and Urbain Le Verrier predicted the position of the planet. A discrepancy in Mercurys orbit pointed out flaws in Newtons theory, the issue was resolved in 1915 by Albert Einsteins new theory of general relativity, which accounted for the small discrepancy in Mercurys orbit. The simplest way to test the equivalence principle is to drop two objects of different masses or compositions in a vacuum and see whether they hit the ground at the same time. Such experiments demonstrate that all objects fall at the rate when other forces are negligible
41.
Radio occultation
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Radio occultation is a remote sensing technique used for measuring the physical properties of a planetary atmosphere or ring system. Atmospheric radio occultation relies on the detection of a change in a signal as it passes through a planets atmosphere. When electromagnetic radiation passes through the atmosphere, it is refracted, the magnitude of the refraction depends on the gradient of refractivity normal to the path, which in turn depends on the density gradient. The effect is most pronounced when the radiation traverses a long atmospheric limb path, at radio frequencies the amount of bending cannot be measured directly, instead the bending can be calculated using the Doppler shift of the signal given the geometry of the emitter and receiver. The amount of bending can be related to the index by using an Abel transform on the formula relating bending angle to refractivity. In the case of the neutral atmosphere information on the temperature, pressure. GNSS or GPS radio occultation is a type of radio occultation relies on radio transmissions from GPS, or more generally from GNSS. This is a new technique for performing atmospheric measurements. It is used as a forecasting tool, and could also be harnessed in monitoring climate change. The technique involves a low-Earth orbit satellite receiving a signal from a GPS satellite, the signal has to pass through the atmosphere and gets refracted along the way. The magnitude of the refraction depends on the temperature and water vapor concentration in the atmosphere, GPS Radio occultation amounts to an almost instantaneous depiction of the atmospheric state. The relative position between the GPS satellite and the low-Earth orbit satellite changes over time, allowing for a vertical scanning of successive layers of the atmosphere, GPSRO observations can also be conducted from aircraft. Current missions include, REX on New Horizons For past missions, see Special, WhatLinksHere/Radio occultation
42.
Turbulence
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Turbulence or turbulent flow is a flow regime in fluid dynamics characterized by chaotic changes in pressure and flow velocity. It is in contrast to a flow regime, which occurs when a fluid flows in parallel layers. Turbulence is caused by kinetic energy in parts of a fluid flow. For this reason turbulence is easier to create in low viscosity fluids, in general terms, in turbulent flow, unsteady vortices appear of many sizes which interact with each other, consequently drag due to friction effects increases. This would increase the energy needed to pump fluid through a pipe, however this effect can also be exploited by such as aerodynamic spoilers on aircraft, which deliberately spoil the laminar flow to increase drag and reduce lift. The onset of turbulence can be predicted by a constant called the Reynolds number. However, turbulence has long resisted detailed physical analysis, and the interactions within turbulence creates a complex situation. Richard Feynman has described turbulence as the most important unsolved problem of classical physics, smoke rising from a cigarette is mostly turbulent flow. However, for the first few centimeters the flow is laminar, the smoke plume becomes turbulent as its Reynolds number increases, due to its flow velocity and characteristic length increasing. If the golf ball were smooth, the boundary layer flow over the front of the sphere would be laminar at typical conditions. However, the layer would separate early, as the pressure gradient switched from favorable to unfavorable. To prevent this happening, the surface is dimpled to perturb the boundary layer. This results in higher skin friction, but moves the point of boundary layer separation further along, resulting in form drag. The flow conditions in industrial equipment and machines. The external flow over all kind of such as cars, airplanes, ships. The motions of matter in stellar atmospheres, a jet exhausting from a nozzle into a quiescent fluid. As the flow emerges into this external fluid, shear layers originating at the lips of the nozzle are created and these layers separate the fast moving jet from the external fluid, and at a certain critical Reynolds number they become unstable and break down to turbulence. Biologically generated turbulence resulting from swimming animals affects ocean mixing, snow fences work by inducing turbulence in the wind, forcing it to drop much of its snow load near the fence
