1.
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
2.
Jet Propulsion Laboratory
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The Jet Propulsion Laboratory is a federally funded research and development center and NASA field center in La Cañada Flintridge, California and Pasadena, California, United States. The JPL is managed by the nearby California Institute of Technology for NASA, the laboratorys primary function is the construction and operation of planetary robotic spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASAs Deep Space Network and they are also responsible for managing the JPL Small-Body Database, and provides physical data and lists of publications for all known small Solar System bodies. The JPLs Space Flight Operations Facility and Twenty-Five-Foot Space Simulator are designated National Historic Landmarks, JPL traces its beginnings to 1936 in the Guggenheim Aeronautical Laboratory at the California Institute of Technology when the first set of rocket experiments were carried out in the Arroyo Seco. Malinas thesis advisor was engineer/aerodynamicist Theodore von Kármán, who arranged for U. S. Army financial support for this GALCIT Rocket Project in 1939. In 1941, Malina, Parsons, Forman, Martin Summerfield, in 1943, von Kármán, Malina, Parsons, and Forman established the Aerojet Corporation to manufacture JATO motors. The project took on the name Jet Propulsion Laboratory in November 1943, during JPLs Army years, the laboratory developed two deployed weapon systems, the MGM-5 Corporal and MGM-29 Sergeant intermediate range ballistic missiles. These missiles were the first US ballistic missiles developed at JPL and it also developed a number of other weapons system prototypes, such as the Loki anti-aircraft missile system, and the forerunner of the Aerobee sounding rocket. At various times, it carried out testing at the White Sands Proving Ground, Edwards Air Force Base. A lunar lander was developed in 1938-39 which influenced design of the Apollo Lunar Module in the 1960s. The team lost that proposal to Project Vanguard, and instead embarked on a project to demonstrate ablative re-entry technology using a Jupiter-C rocket. They carried out three successful flights in 1956 and 1957. Using a spare Juno I, the two organizations then launched the United States first satellite, Explorer 1, on February 1,1958, JPL was transferred to NASA in December 1958, becoming the agencys primary planetary spacecraft center. JPL engineers designed and operated Ranger and Surveyor missions to the Moon that prepared the way for Apollo, JPL also led the way in interplanetary exploration with the Mariner missions to Venus, Mars, and Mercury. In 1998, JPL opened the Near-Earth Object Program Office for NASA, as of 2013, it has found 95% of asteroids that are a kilometer or more in diameter that cross Earths orbit. JPL was early to employ women mathematicians, in the 1940s and 1950s, using mechanical calculators, women in an all-female computations group performed trajectory calculations. In 1961, JPL hired Dana Ulery as their first woman engineer to work alongside male engineers as part of the Ranger and Mariner mission tracking teams, when founded, JPLs site was a rocky flood-plain just outside the city limits of Pasadena. Almost all of the 177 acres of the U. S, the city of La Cañada Flintridge, California was incorporated in 1976, well after JPL attained international recognition with a Pasadena address
3.
Titan IIIE
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The Titan IIIE or Titan 3E, also known as Titan III-Centaur was an American expendable launch system. Launched seven times between 1974 and 1977, it enabled several high-profile NASA missions, including the Voyager and Viking planetary probes, all seven launches were conducted from Launch Complex 41 at Cape Canaveral. With over three times the capacity of the Atlas-Centaur, Titan IIIE would be able to launch ambitious robotic spacecraft missions planned for the 1970s. NASAs Lewis Research Center was given the task of integrating Titan with Centaur, the most obvious change was enclosing Centaur in a large shroud that protected the stage and the payload during ascent. This enabled the use of improved insulation on Centaur, which increased coast time in orbit from 30 minutes when launched on Atlas to over 5 hours on the Titan IIIE, since Centaur was wider than the Titans core stage, a tapering interface was required. This interface had to be insulated to prevent boiloff of Centaurs cryogenic propellants, since Titan used hypergolic propellants stored at ambient temperature, the Centaur stage also contained the guidance computer for the entire launch vehicle. A four-stage configuration, with an upper stage, a Star-37E, was also available. Star-37E stages were used on the two Voyager launches, but were considered to be part of the payload rather than the rocket. The first Titan IIIE launch occurred on February 11,1974, the Titan performed normally, but the Centaurs engines failed to start. Ground controllers waited for a minute, then issued a start command. With the Centaur descending back towards Earth, the range safety destruct command was sent from a station in Antigua. The failure was traced to the Centaur boost pumps, but the cause was still unclear, to reduce the chance of another similar failure, pre-launch procedures to verify Centaurs pumps were free and unobstructed were put in place. It took nearly four years to trace the cause of the failure and this bracket held a LOX regulator in place and the technician responsible for installing it had found that the normal tool used to screw bolts into place was too short to reach the bracket. He thus used a slightly longer socket wrench which gave him more reach, the technician had since retired and failed to inform his successor about this. The new technician thus attempted to attach the bolt with the wrench specified in the assembly instructions, the bolt came loose, fell off, and got sucked into one of the LOX boost pumps, jamming it and preventing it from operating. The next flight of the Titan IIIE was on December 10,1974 and this mission was successful, as were all subsequent launches. Voyager 1s launch almost ended in failure when a fuel line obstruction caused low thrust in the Titan second stage, at cutoff, it was a mere 3.5 seconds from propellant exhaustion. That the mission ultimately succeeded was due to the position of Jupiter vis-a-vis the Earth on launch day
4.
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
5.
Jupiter
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Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a giant planet with a mass one-thousandth that of the Sun, Jupiter and Saturn are gas giants, the other two giant planets, Uranus and Neptune are ice giants. Jupiter has been known to astronomers since antiquity, the Romans named it after their god Jupiter. Jupiter is primarily composed of hydrogen with a quarter of its mass being helium and it may also have a rocky core of heavier elements, but like the other giant planets, Jupiter lacks a well-defined solid surface. Because of its rotation, the planets shape is that of an oblate spheroid. The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence, a prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope. Surrounding Jupiter is a faint planetary ring system and a powerful magnetosphere, Jupiter has at least 67 moons, including the four large Galilean moons discovered by Galileo Galilei in 1610. Ganymede, the largest of these, has a greater than that of the planet Mercury. Jupiter has been explored on several occasions by robotic spacecraft, most notably during the early Pioneer and Voyager flyby missions and later by the Galileo orbiter. In late February 2007, Jupiter was visited by the New Horizons probe, the latest probe to visit the planet is Juno, which entered into orbit around Jupiter on July 4,2016. Future targets for exploration in the Jupiter system include the probable ice-covered liquid ocean of its moon Europa, Earth and its neighbor planets may have formed from fragments of planets after collisions with Jupiter destroyed those super-Earths near the Sun. Astronomers have discovered nearly 500 planetary systems with multiple planets, Jupiter moving out of the inner Solar System would have allowed the formation of inner planets, including Earth. Jupiter is composed primarily of gaseous and liquid matter and it is the largest of the four giant planets in the Solar System and hence its largest planet. It has a diameter of 142,984 km at its equator, the average density of Jupiter,1.326 g/cm3, is the second highest of the giant planets, but lower than those of the four terrestrial planets. Jupiters upper atmosphere is about 88–92% hydrogen and 8–12% helium by percent volume of gas molecules, a helium atom has about four times as much mass as a hydrogen atom, so the composition changes when described as the proportion of mass contributed by different atoms. Thus, Jupiters atmosphere is approximately 75% hydrogen and 24% helium by mass, the atmosphere contains trace amounts of methane, water vapor, ammonia, and silicon-based compounds. There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, the outermost layer of the atmosphere contains crystals of frozen ammonia. The interior contains denser materials - by mass it is roughly 71% hydrogen, 24% helium, through infrared and ultraviolet measurements, trace amounts of benzene and other hydrocarbons have also been found
6.
Saturn
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Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with a radius about nine times that of Earth. Although it has only one-eighth the average density of Earth, with its larger volume Saturn is just over 95 times more massive, Saturn is named after the Roman god of agriculture, its astronomical symbol represents the gods sickle. Saturns interior is composed of a core of iron–nickel and rock. This core is surrounded by a layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium. Saturn has a yellow hue due to ammonia crystals in its upper atmosphere. Saturns magnetic field strength is around one-twentieth of Jupiters, the outer atmosphere is generally bland and lacking in contrast, although long-lived features can appear. Wind speeds on Saturn can reach 1,800 km/h, higher than on Jupiter, sixty-two moons are known to orbit Saturn, of which fifty-three are officially named. This does not include the hundreds of moonlets comprising the rings, Saturn is a gas giant because it is predominantly composed of hydrogen and helium. It lacks a definite surface, though it may have a solid core, Saturns rotation causes it to have the shape of an oblate spheroid, that is, it is flattened at the poles and bulges at its equator. Its equatorial and polar radii differ by almost 10%,60,268 km versus 54,364 km, Jupiter, Uranus, and Neptune, the other giant planets in the Solar System, are also oblate but to a lesser extent. Saturn is the planet of the Solar System that is less dense than water—about 30% less. Although Saturns core is considerably denser than water, the specific density of the planet is 0.69 g/cm3 due to the atmosphere. Jupiter has 318 times the Earths mass, while Saturn is 95 times the mass of the Earth, together, Jupiter and Saturn hold 92% of the total planetary mass in the Solar System. On 8 January 2015, NASA reported determining the center of the planet Saturn, the temperature, pressure, and density inside Saturn all rise steadily toward the core, which causes hydrogen to transition into a metal in the deeper layers. Standard planetary models suggest that the interior of Saturn is similar to that of Jupiter, having a rocky core surrounded by hydrogen. This core is similar in composition to the Earth, but more dense, in 2004, they estimated that the core must be 9–22 times the mass of the Earth, which corresponds to a diameter of about 25,000 km. This is surrounded by a liquid metallic hydrogen layer, followed by a liquid layer of helium-saturated molecular hydrogen that gradually transitions to a gas with increasing altitude
7.
Titan (moon)
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Titan is the largest moon of Saturn. It is the only known to have a dense atmosphere. Titan is the sixth ellipsoidal moon from Saturn, frequently described as a planet-like moon, Titan is 50% larger than Earths Moon, and it is 80% more massive. It is the second-largest moon in the Solar System, after Jupiters moon Ganymede, and is larger than the smallest planet, Mercury, discovered in 1655 by the Dutch astronomer Christiaan Huygens, Titan was the first known moon of Saturn, and the sixth known planetary satellite. Titan orbits Saturn at 20 Saturn radii, from Titans surface, Saturn subtends an arc of 5.09 degrees and would appear 11.4 times larger in the sky than the Moon from Earth. Titan is primarily composed of ice and rocky material. The geologically young surface is smooth, with few impact craters, although mountains. The atmosphere of Titan is largely nitrogen, minor components lead to the formation of methane and ethane clouds and nitrogen-rich organic smog. The climate—including wind and rain—creates surface features similar to those of Earth, such as dunes, rivers, lakes, seas, and deltas, Huygens was inspired by Galileos discovery of Jupiters four largest moons in 1610 and his improvements in telescope technology. Christiaan, with the help of his brother Constantijn Huygens, Jr. began building telescopes around 1650 and it was the sixth moon to be discovered. He named it Saturni Luna, publishing in the 1655 tract De Saturni Luna Observatio Nova, after Giovanni Domenico Cassini published his discoveries of four more moons of Saturn between 1673 and 1686, astronomers fell into the habit of referring to these and Titan as Saturn I through V. Other early epithets for Titan include Saturns ordinary satellite, Titan is officially numbered Saturn VI because after the 1789 discoveries the numbering scheme was frozen to avoid causing any more confusion. Numerous small moons have been discovered closer to Saturn since then and he suggested the names of the mythological Titans, brothers and sisters of Cronus, the Greek Saturn. In Greek mythology, the Titans were a race of powerful deities, descendants of Gaia and Uranus, Titan orbits Saturn once every 15 days and 22 hours. Because of this, there is a point on its surface. Longitudes on Titan are measured westward, starting from the passing through this point. Its orbital eccentricity is 0.0288, and the plane is inclined 0.348 degrees relative to the Saturnian equator. Viewed from Earth, Titan reaches a distance of about 20 Saturn radii from Saturn
8.
Flagship Program
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The Flagship Program is a series of NASA missions to explore the Solar System. It is the largest and most expensive of three classes of NASA Solar System Programs, the two being the medium-cost New Frontiers Program and the lowest-cost Discovery Program. According to NASA, the cost of a Flagship-class mission is over $1 billion and these missions will be crucial in allowing humans to reach and explore high-priority targets. These critically important targets could help establish the limits of habitability, not just for the Solar System. In particular, they provide an opportunity to identify prebiotic organic molecules or even extant life beyond Earth, should it exist. The Flagship program includes the Viking probes, the Voyager probes, the Galileo spacecraft, the Cassini spacecraft, the Chandra X-Ray Observatory, proposed programs in the estimated range $1 billion and $3 billion include the Mars 2020, and Europa Multiple-Flyby Mission. And the modern NASA program which includes Flagships, in the early 1990s, NASA made the decision that instead of a centrally planned mission approach around pre-selected targets, mission ideas would compete for selection. The competitions would be based in cost categories, eventually turning into the Discovery, New Frontiers, while teams self-assemble to compete for Discovery and New Frontiers missions, Flagship programs are still strongly influenced by NASA headquarters. Other priorities included the Uranus Orbiter and Probe, the Enceladus Orbiter, at that time, all proposed NASA Flagship planetary missions were put on hold indefinitely. However, in December 2012, the Mars 2020 sample-caching rover, more recently, in June 2015, the Europa Multiple-Flyby Mission was approved by NASA and entered the formulation stage. ExoMars Jupiter Europa Orbiter Mars Science Laboratory Outer Planet Flagship Mission
9.
Voyager 2
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Voyager 2 is a space probe launched by NASA on August 20,1977, to study the outer planets. Part of the Voyager program, it was launched 16 days before its twin, Voyager 1, on a trajectory that took longer to reach Jupiter and Saturn but enabled further encounters with Uranus and it is the only spacecraft to have visited either of the ice giants. Voyager 2 is now in its mission to study the outer reaches of the Solar System and has been operating for 39 years,7 months and 17 days. It remains in contact through the Deep Space Network, at a distance of 114 AU from the Sun as of April 5th,2017, Voyager 2 is one of the most distant human-made objects, along with Voyager 1, New Horizons, Pioneer 10 and Pioneer 11. The probe was moving at a velocity of 15.4 km/s relative to the Sun as of December 2014 and is traveling through the heliosheath, upon reaching interstellar space, Voyager 2 is expected to provide the first direct measurements of the density and temperature of the interstellar plasma. The spacecraft would be designed with redundant systems to ensure survival through the entire tour, by 1972 the mission was scaled back and replaced with two Mariner-derived spacecraft, the Mariner Jupiter-Saturn probes. To keep apparent lifetime program costs low, the mission would include only flybys of Jupiter and Saturn, as the program progressed, the name was changed to Voyager. The primary mission of Voyager 1 was to explore Jupiter, Saturn, Voyager 2 was also to explore Jupiter and Saturn, but on a trajectory that would have option of continuing on to Uranus and Neptune, or being redirected to Titan as a backup for Voyager 1. Upon successful completion of Voyager 1s objectives, Voyager 2 would get an extension to send the probe on towards Uranus. Collectively these instruments are part of the Attitude and Articulation Control Subsystem along with redundant units of most instruments and 8 backup thrusters, the spacecraft also included 11 scientific instruments to study celestial objects as it traveled through space. Built with the intent for eventual interstellar travel, Voyager 2 included a large,3.7 m parabolic, when the spacecraft is unable to communicate with Earth, the Digital Tape Recorder can record about 64 kilobytes of data for transmission at another time. The spacecraft was built with 3 Multihundred-Watt radioisotope thermoelectric generators, each RTG includes 24 pressed plutonium oxide spheres and provides enough heat to generate approximately 157 watts of power at launch. Collectively, the RTGs supply the spacecraft with 470 watts at launch, for more details on the Voyager space probes identical instrument packages, see the separate article on the overall Voyager Program. The Voyager 2 probe was launched on August 20,1977, by NASA from Space Launch Complex 41 at Cape Canaveral, Florida, two weeks later, the twin Voyager 1 probe would be launched on September 5,1977. However, Voyager 1 would reach both Jupiter and Saturn sooner, as Voyager 2 had been launched into a longer, more circular trajectory, Voyager 2s closest approach to Jupiter occurred on July 9,1979. It came within 570,000 km of the cloud tops. It discovered a few rings around Jupiter, as well as volcanic activity on the moon Io, the Great Red Spot was revealed as a complex storm moving in a counterclockwise direction. An array of other storms and eddies were found throughout the banded clouds
10.
Galileo (spacecraft)
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Galileo was an American unmanned spacecraft that studied the planet Jupiter and its moons, as well as several other Solar System bodies. Named after the astronomer Galileo Galilei, it consisted of an orbiter and it was launched on October 18,1989, carried by Space Shuttle Atlantis, on the STS-34 mission. Galileo arrived at Jupiter on December 7,1995, after gravitational assist flybys of Venus and Earth and it launched the first probe into Jupiter, directly measuring its atmosphere. Despite suffering major antenna problems, Galileo achieved the first asteroid flyby, of 951 Gaspra, in 1994, Galileo observed Comet Shoemaker–Levy 9s collision with Jupiter. Jupiters atmospheric composition and ammonia clouds were recorded, the clouds possibly created by outflows from the depths of the atmosphere. Ios volcanism and plasma interactions with Jupiters atmosphere were also recorded, Ganymede was shown to possess a magnetic field and the spacecraft found new evidence for exospheres around Europa, Ganymede, and Callisto. Galileo also discovered that Jupiters faint ring system consists of dust from impacts on the four inner moons. The extent and structure of Jupiters magnetosphere was also mapped, Jupiter was rated as the number one priority in the Planetary Science Decadal Survey published in the summer of 1968. In the early 1970s the first flybys of Jupiter were achieved by Pioneer 10 and Pioneer 11, work on the spacecraft began at Jet Propulsion Laboratory in 1977, while the Voyager 1 and 2 missions were still being prepared for launch. As the shuttle program got underway, Galileo was scheduled for launch in 1984, the mission was initially called the Jupiter Orbiter Probe, it was christened Galileo in 1978. Once the spacecraft was complete, its launch was scheduled for STS-61-G on-board Atlantis in 1986, the Inertial Upper Stage booster was going to be used at first, but this changed to the Centaur booster, then back to IUS after Challenger. The Centaur-G liquid hydrogen-fueled booster stage allowed a direct trajectory to Jupiter, however, the mission was further delayed by the hiatus in launches that occurred after the Space Shuttle Challenger disaster. New safety protocols introduced as a result of the disaster prohibited the use of the Centaur-G stage on the Shuttle and it was finally launched on October 18,1989, by Space Shuttle Atlantis on the STS-34 mission. Venus was flown by at 05,58,48 UTC on February 10,1990, at a range of 16,106 km. Galileo then performed a flyby of Earth at 303.1 km at 15,09,25 UTC on December 8,1992. Galileo performed close observations of an asteroid,243 Ida, at 16,51,59 UTC on August 28,1993. The spacecraft discovered Ida has a moon, Dactyl, the first discovery of a satellite orbiting an asteroid. Galileos prime mission was a study of the Jovian system
11.
Space probe
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A space probe is a robotic spacecraft that does not orbit the Earth, but, instead, explores further into outer space. A space probe may approach the Moon, travel through space, flyby, orbit, or land on other planetary bodies. Approximately fifteen missions are currently operational, once a probe has left the vicinity of Earth, its trajectory will likely take it along an orbit around the Sun similar to the Earths orbit. To reach another planet, the simplest practical method is a Hohmann transfer orbit, more complex techniques, such as gravitational slingshots, can be more fuel-efficient, though they may require the probe to spend more time in transit. Some high Delta-V missions can only be performed, within the limits of modern propulsion, a technique using very little propulsion, but requiring a considerable amount of time, is to follow a trajectory on the Interplanetary Transport Network. First man-made object to land on the Moon, or any other extra terrestrial surface. First mission to photograph the far side of the Moon, launched in 1959, first robotic sample return probe from the Moon. It was sent to the Moon on November 10,1970, first successful in-place analysis of another planet. It may have also been the first space probe to impact the surface of another planet, the Venera 7 probe was the first spacecraft to successfully soft land on another planet and to transmit data from there back to Earth. Upon its arrival at Mars on November 13,1971, Mariner 9 became the first space probe to orbit around another planet. Although, the spacecraft failed shortly after landing, the Mars Exploration Rovers, Spirit and Opportunity surface and geology, and searched for clues to past water activity on Mars. They were each launched in 2003 and landed in 2004, communication with Spirit stopped on sol 2210. JPL continued to attempt to regain contact until May 24,2011, Opportunity arrived at Endeavour crater on 9 August 2011, at a landmark called Spirit Point named after its rover twin, after traversing 13 miles from Victoria crater, over a three-year period. As of January 26,2016, Opportunity has lasted for more than twelve years on Mars — although the rovers were intended to last only three months. The first dedicated missions to a comet, in this case and they dropped landers and balloons at Venus before their rendezvous with Halleys Comet. This Japanese probe was the first non-US, non-Soviet interplanetary probe, a second Japanese probe, it made ultraviolet wavelength observations of the comet. The first space probe to penetrate a comets coma and take images of its nucleus. First solar wind sample return probe from sun-earth L1, first sample return probe from a comet tail
12.
Voyager program
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The Voyager program is a continuing American scientific program that employs two robotic probes, Voyager 1 and Voyager 2, to study the outer Solar System. They were launched in 1977 to take advantage of an alignment of Jupiter, Saturn, Uranus, and Neptune. Their mission has been extended three times, and both continue to collect and relay useful scientific data. Neither Uranus nor Neptune has been visited by any other than Voyager 2. On August 25,2012, data from Voyager 1 indicated that it had become the first human-made object to enter space, traveling further than anyone, or anything. As of 2013, Voyager 1 was moving with a velocity of 17 kilometers per second relative to the Sun, Data and photographs collected by the Voyagers cameras, magnetometers, and other instruments revealed previously unknown details about each of the giant planets and their moons. Close-up images from the spacecraft charted Jupiter’s complex cloud forms, winds, saturn’s rings were found to have enigmatic braids, kinks, and spokes and to be accompanied by myriad ringlets. At Uranus Voyager 2 discovered a magnetic field around the planet and 10 additional moons. Its flyby of Neptune uncovered three complete rings and six hitherto unknown moons as well as a magnetic field and complex. Voyager 2 is still the only spacecraft to have visited the ice giants, the two Voyager space probes were originally conceived as part of the Mariner program, and they were thus initially named Mariner 11 and Mariner 12. The Voyager Program was similar to the Planetary Grand Tour planned during the late 1960s, the Grand Tour would take advantage of an alignment of the outer planets discovered by Gary Flandro, an aerospace engineer at the Jet Propulsion Laboratory. This alignment, which occurs once every 175 years, would occur in the late 1970s and make it possible to use gravitational assists to explore Jupiter, Saturn, Uranus, Neptune, and Pluto. The Planetary Grand Tour was to several pairs of probes to fly by all the outer planets along various trajectories, including Jupiter-Saturn-Pluto. Limited funding ended the Grand Tour program, but elements were incorporated into the Voyager Program, Voyager 2 was the first to launch. Its trajectory was designed to allow flybys of Jupiter, Saturn, Uranus and this encounter sent Voyager 1 out of the plane of the ecliptic, ending its planetary science mission. Had Voyager 1 been unable to perform the Titan flyby, the trajectory of Voyager 2 could have altered to explore Titan, forgoing any visit to Uranus. Voyager 1 was not launched on a trajectory that would have allowed it to continue to Uranus and Neptune, but could have continued from Saturn to Pluto without exploring Titan. The New Horizons probe, which had a higher velocity than Voyager 1, is traveling more slowly due to the extra speed Voyager 1 gained from its flybys of Jupiter
13.
Solar System
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The Solar System is the gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly. Of those objects that orbit the Sun directly, the largest eight are the planets, with the remainder being significantly smaller objects, such as dwarf planets, of the objects that orbit the Sun indirectly, the moons, two are larger than the smallest planet, Mercury. The Solar System formed 4.6 billion years ago from the collapse of a giant interstellar molecular cloud. The vast majority of the mass is in the Sun. The four smaller inner planets, Mercury, Venus, Earth and Mars, are terrestrial planets, being composed of rock. The four outer planets are giant planets, being more massive than the terrestrials. All planets have almost circular orbits that lie within a flat disc called the ecliptic. The Solar System also contains smaller objects, the asteroid belt, which lies between the orbits of Mars and Jupiter, mostly contains objects composed, like the terrestrial planets, of rock and metal. Beyond Neptunes orbit lie the Kuiper belt and scattered disc, which are populations of trans-Neptunian objects composed mostly of ices, within these populations are several dozen to possibly tens of thousands of objects large enough that they have been rounded by their own gravity. Such objects are categorized as dwarf planets, identified dwarf planets include the asteroid Ceres and the trans-Neptunian objects Pluto and Eris. In addition to two regions, various other small-body populations, including comets, centaurs and interplanetary dust clouds. Six of the planets, at least four of the dwarf planets, each of the outer planets is encircled by planetary rings of dust and other small objects. The solar wind, a stream of charged particles flowing outwards from the Sun, the heliopause is the point at which pressure from the solar wind is equal to the opposing pressure of the interstellar medium, it extends out to the edge of the scattered disc. The Oort cloud, which is thought to be the source for long-period comets, the Solar System is located in the Orion Arm,26,000 light-years from the center of the Milky Way. For most of history, humanity did not recognize or understand the concept of the Solar System, the invention of the telescope led to the discovery of further planets and moons. The principal component of the Solar System is the Sun, a G2 main-sequence star that contains 99. 86% of the known mass. The Suns four largest orbiting bodies, the giant planets, account for 99% of the mass, with Jupiter. The remaining objects of the Solar System together comprise less than 0. 002% of the Solar Systems total mass, most large objects in orbit around the Sun lie near the plane of Earths orbit, known as the ecliptic
14.
NASA Deep Space Network
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It also performs radio and radar astronomy observations for the exploration of the solar system and the universe, and supports selected Earth-orbiting missions. DSN is part of the NASA Jet Propulsion Laboratory, similar networks are run by Europe, Russia, China, India, and Japan. DSN currently consists of three deep-space communications facilities placed approximately 120 degrees apart around the Earth and they are, the Goldstone Deep Space Communications Complex outside Barstow, California. Each facility is situated in semi-mountainous, bowl-shaped terrain to shield against radio frequency interference. All DSN antennas are steerable, high-gain, parabolic reflector antennas, the antennas and data delivery systems make it possible to, acquire telemetry data from spacecraft. Perform Very Long Baseline Interferometry observations, measure variations in radio waves for radio science experiments. Monitor and control the performance of the network, the antennas at all three DSN Complexes communicate directly with the Deep Space Operations Center located at the JPL facilities in Pasadena, California. In the early years, the control center did not have a permanent facility. It was a setup with numerous desks and phones installed in a large room near the computers used to calculate orbits. In July 1961, NASA started the construction of the permanent facility, the facility was completed in October 1963 and dedicated on May 14,1964. In the initial setup of the SFOF, there were 31 consoles,100 closed-circuit television cameras, currently, the operations center personnel at SFOF monitor and direct operations, and oversee the quality of spacecraft telemetry and navigation data delivered to network users. Tracking vehicles in space is quite different from tracking missions in low Earth orbit. Deep space missions are visible for long periods of time from a portion of the Earths surface. These few stations, however, require huge antennas, ultra-sensitive receivers, Deep space is defined in several different ways. According to a 1975 NASA report, the DSN was designed to communicate with spacecraft traveling approximately 16,000 km from Earth to the farthest planets of the solar system. JPL diagrams state that at an altitude of 30,000 km and this definition means that missions to the Moon, and the Earth–Sun Lagrangian points L1 and L2, are considered near space and cannot use the ITUs deep space bands. Other Lagrangian points may or may not be subject to rule due to distance. NASA was officially established on October 1,1958, to consolidate the separately developing space-exploration programs of the US Army, US Navy, the DSN was given responsibility for its own research, development, and operation in support of all of its users
15.
Pluto
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Pluto is a dwarf planet in the Kuiper belt, a ring of bodies beyond Neptune. It was the first Kuiper belt object to be discovered, Pluto was discovered by Clyde Tombaugh in 1930 and was originally considered to be the ninth planet from the Sun. After 1992, its planethood was questioned following the discovery of objects of similar size in the Kuiper belt. In 2005, Eris, which is 27% more massive than Pluto, was discovered and this led the International Astronomical Union to define the term planet formally in 2006, during their 26th General Assembly. That definition excluded Pluto and reclassified it as a dwarf planet, Pluto is the largest and second-most-massive known dwarf planet in the Solar System and the ninth-largest and tenth-most-massive known object directly orbiting the Sun. It is the largest known trans-Neptunian object by volume but is less massive than Eris, like other Kuiper belt objects, Pluto is primarily made of ice and rock and is relatively small—about one-sixth the mass of the Moon and one-third its volume. It has an eccentric and inclined orbit during which it ranges from 30 to 49 astronomical units or AU from the Sun. This means that Pluto periodically comes closer to the Sun than Neptune, light from the Sun takes about 5.5 hours to reach Pluto at its average distance. Pluto has five moons, Charon, Styx, Nix, Kerberos. Pluto and Charon are sometimes considered a system because the barycenter of their orbits does not lie within either body. The IAU has not formalized a definition for binary dwarf planets, on July 14,2015, the New Horizons spacecraft became the first spacecraft to fly by Pluto. During its brief flyby, New Horizons made detailed measurements and observations of Pluto, on October 25,2016, at 05,48 pm ET, the last bit of data was received from New Horizons from its close encounter with Pluto on July 14,2015. In the 1840s, Urbain Le Verrier used Newtonian mechanics to predict the position of the then-undiscovered planet Neptune after analysing perturbations in the orbit of Uranus. Subsequent observations of Neptune in the late 19th century led astronomers to speculate that Uranuss orbit was being disturbed by another planet besides Neptune, by 1909, Lowell and William H. Pickering had suggested several possible celestial coordinates for such a planet. Lowell and his observatory conducted his search until his death in 1916, unknown to Lowell, his surveys had captured two faint images of Pluto on March 19 and April 7,1915, but they were not recognized for what they were. There are fourteen other known prediscovery observations, with the oldest made by the Yerkes Observatory on August 20,1909. Percivals widow, Constance Lowell, entered into a legal battle with the Lowell Observatory over her late husbands legacy. Tombaughs task was to image the night sky in pairs of photographs, then examine each pair
16.
Natural satellite
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A natural satellite or moon is, in the most common usage, an astronomical body that orbits a planet or minor planet. In the Solar System there are six planetary satellite systems containing 178 known natural satellites, four IAU-listed dwarf planets are also known to have natural satellites, Pluto, Haumea, Makemake, and Eris. As of January 2012, over 200 minor-planet moons have been discovered, the Earth–Moon system is unique in that the ratio of the mass of the Moon to the mass of Earth is much greater than that of any other natural-satellite–planet ratio in the Solar System. At 3,474 km across, Earths Moon is 0.27 times the diameter of Earth, the first known natural satellite was the Moon, but it was considered a planet until Copernicus introduction of heliocentrism in 1543. Until the discovery of the Galilean satellites in 1610, however, galileo chose to refer to his discoveries as Planetæ, but later discoverers chose other terms to distinguish them from the objects they orbited. The first to use of the satellite to describe orbiting bodies was the German astronomer Johannes Kepler in his pamphlet Narratio de Observatis a se quatuor Iouis satellitibus erronibus in 1610. He derived the term from the Latin word satelles, meaning guard, attendant, or companion, the term satellite thus became the normal one for referring to an object orbiting a planet, as it avoided the ambiguity of moon. In 1957, however, the launching of the artificial object Sputnik created a need for new terminology, to further avoid ambiguity, the convention is to capitalize the word Moon when referring to Earths natural satellite, but not when referring to other natural satellites. A few recent authors define moon as a satellite of a planet or minor planet, there is no established lower limit on what is considered a moon. Small asteroid moons, such as Dactyl, have also been called moonlets, the upper limit is also vague. Two orbiting bodies are described as a double body rather than primary. Asteroids such as 90 Antiope are considered double asteroids, but they have not forced a clear definition of what constitutes a moon, some authors consider the Pluto–Charon system to be a double planet. In contrast, irregular satellites are thought to be captured asteroids possibly further fragmented by collisions, most of the major natural satellites of the Solar System have regular orbits, while most of the small natural satellites have irregular orbits. The Moon and possibly Charon are exceptions among large bodies in that they are thought to have originated by the collision of two large proto-planetary objects. The material that would have placed in orbit around the central body is predicted to have reaccreted to form one or more orbiting natural satellites. As opposed to planetary-sized bodies, asteroid moons are thought to form by this process. Triton is another exception, although large and in a close, circular orbit, its motion is retrograde, most regular moons in the Solar System are tidally locked to their respective primaries, meaning that the same side of the natural satellite always faces its planet. The only known exception is Saturns natural satellite Hyperion, which rotates chaotically because of the influence of Titan
17.
Escape velocity
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The escape velocity from Earth is about 11.186 km/s at the surface. More generally, escape velocity is the speed at which the sum of a kinetic energy. With escape velocity in a direction pointing away from the ground of a massive body, once escape velocity is achieved, no further impulse need be applied for it to continue in its escape. When given a speed V greater than the speed v e. In these equations atmospheric friction is not taken into account, escape velocity is only required to send a ballistic object on a trajectory that will allow the object to escape the gravity well of the mass M. The existence of escape velocity is a consequence of conservation of energy, by adding speed to the object it expands the possible places that can be reached until with enough energy they become infinite. For a given gravitational potential energy at a position, the escape velocity is the minimum speed an object without propulsion needs to be able to escape from the gravity. Escape velocity is actually a speed because it does not specify a direction, no matter what the direction of travel is, the simplest way of deriving the formula for escape velocity is to use conservation of energy. Imagine that a spaceship of mass m is at a distance r from the center of mass of the planet and its initial speed is equal to its escape velocity, v e. At its final state, it will be a distance away from the planet. The same result is obtained by a calculation, in which case the variable r represents the radial coordinate or reduced circumference of the Schwarzschild metric. All speeds and velocities measured with respect to the field, additionally, the escape velocity at a point in space is equal to the speed that an object would have if it started at rest from an infinite distance and was pulled by gravity to that point. In common usage, the point is on the surface of a planet or moon. On the surface of the Earth, the velocity is about 11.2 km/s. However, at 9,000 km altitude in space, it is less than 7.1 km/s. The escape velocity is independent of the mass of the escaping object and it does not matter if the mass is 1 kg or 1,000 kg, what differs is the amount of energy required. For an object of mass m the energy required to escape the Earths gravitational field is GMm / r, a related quantity is the specific orbital energy which is essentially the sum of the kinetic and potential energy divided by the mass. An object has reached escape velocity when the orbital energy is greater or equal to zero
18.
Heliopause (astronomy)
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The heliosphere is the bubble-like region of space dominated by the Sun, which extends far beyond the orbit of Pluto. The solar wind flows outward from the Sun until encountering the termination shock, the overall shape of the heliosphere is controlled by the interstellar medium through which it is traveling, as well as the Sun, and is not perfectly spherical. The limited data available and unexplored nature of structures have resulted in many theories. On September 12,2013, NASA announced that Voyager 1 had exited the heliosphere on August 25,2012, originating at the extremely hot surface of the corona, solar wind particles reach escape velocity, streaming outwards at 300 to 800 km/s. As it begins to interact with the medium, its velocity slows before finally stopping altogether. The termination shock was traversed by Voyager 1 in 2004, and it may be a more gentle bow wave. Voyager data led to a new theory that the heliosheath has magnetic bubbles, the stagnation region within the heliosheath, starting around 113 au, was detected by Voyager 1 in 2010. There the solar wind velocity drops to zero, the field intensity doubles. Starting in May 2012 at 120 au, Voyager 1 detected an increase in cosmic rays. In the summer of 2013 NASA announced that Voyager 1 had reached interstellar space as of August 25,2012, cassini and IBEX data challenged the heliotail theory in 2009. In July 2013, IBEX results revealed a 4-lobed tail on the Solar Systems heliosphere, the solar wind consists of particles and fields. Because the Sun rotates once approximately every 25 days, the magnetic field transported by the wind gets wrapped into a spiral. Variations in the Suns magnetic field are carried outward by the solar wind, the heliospheric current sheet is a ripple in the heliosphere created by the rotating magnetic field of the Sun. Extending throughout the heliosphere, it is considered the largest structure in the Solar System and is said to resemble a ballerinas skirt, the outer structure of the heliosphere is determined by the interactions between the solar wind and the winds of interstellar space. The solar wind away from the Sun in all directions at speeds of several hundred km/s in the Earths vicinity. At some distance from the Sun, well beyond the orbit of Neptune and this takes place in several stages, The solar wind is traveling at supersonic speeds within the Solar System. At the termination shock, a shock wave, the solar wind falls below the speed of sound. However, observations in 2009 showed that model is incorrect
19.
Interstellar medium
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In astronomy, the interstellar medium is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and it fills interstellar space and blends smoothly into the surrounding intergalactic space. The energy that occupies the same volume, in the form of radiation, is the interstellar radiation field. The interstellar medium is composed of phases, distinguished by whether matter is ionic, atomic, or molecular. The interstellar medium is composed primarily of hydrogen followed by helium with trace amounts of carbon, oxygen, the thermal pressures of these phases are in rough equilibrium with one another. Magnetic fields and turbulent motions also provide pressure in the ISM, in all phases, the interstellar medium is extremely tenuous by terrestrial standards. In cool, dense regions of the ISM, matter is primarily in molecular form, in hot, diffuse regions of the ISM, matter is primarily ionized, and the density may be as low as 10−4 ions per cm3. Compare this with a density of roughly 1019 molecules per cm3 for air at sea level. By mass, 99% of the ISM is gas in any form, and 1% is dust. Of the gas in the ISM, by number 91% of atoms are hydrogen and 9% are helium, with 0. 1% being atoms of elements heavier than hydrogen or helium, by mass this amounts to 70% hydrogen, 28% helium, and 1. 5% heavier elements. The hydrogen and helium are primarily a result of primordial nucleosynthesis, the ISM plays a crucial role in astrophysics precisely because of its intermediate role between stellar and galactic scales. Stars form within the densest regions of the ISM, molecular clouds, and replenish the ISM with matter and energy through planetary nebulae, stellar winds, and supernovae. This interplay between stars and the ISM helps determine the rate at which a galaxy depletes its gaseous content, voyager 1 reached the ISM on August 25,2012, making it the first artificial object from Earth to do so. Interstellar plasma and dust will be studied until the end in 2025. Table 1 shows a breakdown of the properties of the components of the ISM of the Milky Way, field, Goldsmith & Habing put forward the static two phase equilibrium model to explain the observed properties of the ISM. Their modeled ISM consisted of a dense phase, consisting of clouds of neutral and molecular hydrogen. McKee & Ostriker added a third phase that represented the very hot gas which had been shock heated by supernovae. These phases are the temperatures where heating and cooling can reach a stable equilibrium and their paper formed the basis for further study over the past three decades
20.
Radioisotope thermoelectric generator
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This generator has no moving parts. RTGs have been used as sources in satellites, space probes. Safe use of RTGs requires containment of the radioisotopes long after the life of the unit. The RTG was invented in 1954 by Mound Laboratories scientists Ken Jordan and they were inducted into the National Inventors Hall of Fame in 2013. RTGs were developed in the US during the late 1950s by Mound Laboratories in Miamisburg, the project was led by Dr. Bertram C. The first RTG launched into space by the United States was SNAP 3B in 1961 powered by 96 grams of plutonium-238 metal, one of the first terrestrial uses of RTGs was in 1966 by the US Navy at uninhabited Fairway Rock in Alaska. RTGs were used at that site until 1995, a common RTG application is spacecraft power supply. Systems for Nuclear Auxiliary Power units were used for probes that traveled far from the Sun rendering solar panels impractical. As such, they were used with Pioneer 10, Pioneer 11, Voyager 1, Voyager 2, Galileo, Ulysses, Cassini, New Horizons and the Mars Science Laboratory. RTGs were used to power the two Viking landers and for the scientific experiments left on the Moon by the crews of Apollo 12 through 17. Because the Apollo 13 moon landing was aborted, its RTG rests in the South Pacific Ocean, RTGs were also used for the Nimbus, Transit and LES satellites. By comparison, only a few vehicles have been launched using full-fledged nuclear reactors, the Soviet RORSAT series. In addition to spacecraft, the Soviet Union constructed many unmanned lighthouses, powered by strontium-90, they are very reliable and provide a steady source of power. In one instance, the compartments were opened by a thief. In another case, three woodsmen in Tsalendzhikha Region, Georgia came across two ceramic RTG heat sources that had stripped of their shielding. Two of the three were hospitalized with severe radiation burns after carrying the sources on their backs. The units were eventually recovered and isolated, there are approximately 1,000 such RTGs in Russia. All of them have long exhausted their 10-year engineered life spans and they are likely no longer functional, and may be in need of dismantling
21.
Grand Tour program
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The Grand Tour was a NASA program that would have sent two groups of robotic probes to all the planets of the outer Solar System. It called for four spacecraft, two of which would visit Jupiter, Saturn, and Pluto, while the two would visit Jupiter, Uranus, and Neptune. The enormous cost of the project, around $1 billion, led to its cancellation and replacement with Mariner Jupiter-Saturn, the particular alignment occurs once every 175 years. By 1966, JPL was promoting the project, noting it would allow a complete survey of the planets in less time. In 1969, NASA created the Outer Planets Working Group, which favored the concept of two missions that would visit three planets each and these missions were referred to as the Grand Tour. One would launch in 1977 and visit Jupiter, Saturn, and Pluto, while the other would launch in 1979 and visit Jupiter, Uranus and this would reduce total mission time compared to a single Grand Tour from over thirteen years to seven and a half years. The Working Group also called for the development of a new spacecraft to carry out the flyby missions and these probes, called Thermoelectric Outer Planets Spacecraft, were being designed at JPL and featured an operational life of over ten years. By 1971, the estimated cost of Grand Tour was $750 to $900 million, congressional pressure, combined with internal competition from the recently approved Space Shuttle program, led to the decision to cancel the project in December 1971. The Grand Tour and TOPS were replaced with a proposal to only two planets using a pair of Mariner-derived probes. The Mariner Jupiter-Saturn project was approved in early 1972, with an estimated cost of $360 million, the probes were to visit Jupiter, Saturn, and Saturns moon Titan. One was designated JST, its mission would take it to Jupiter, Saturn, the second was designated JSX, it would be launched on a trajectory that would preserve the option of a Grand Tour, while serving as backup for the first probe. It would arrive after JST, and if JST were successful, if JST was unsuccessful, JSX could be diverted to perform the Titan flyby itself. In March 1977, just a few months before launch, NASA held a competition to rename the project, the two spacecraft that launched retained the same mission concept. Voyager 1s course was optimized for the Titan flyby and Voyager 2 for the Grand Tour, Voyager 2 would reach Saturn nine months after Voyager 1, giving plenty of time to decide if it should proceed with the Grand Tour. Additionally, by launching Voyager 2 first, Voyager 1s launch could be re-targeted to perform the Grand Tour if Voyager 2 were lost in a launch failure. With Voyager 1s mission complete, Voyager 2 was cleared for a mission to Uranus and Neptune. Note, Pluto was classified as a planet when the Grand Tour was proposed and at the time New Horizons was launched
22.
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
23.
Mariner program
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The program included a number of firsts, including the first planetary flyby, the first planetary orbiter, and the first gravity assist maneuver. Of the ten vehicles in the Mariner series, seven were successful, other Mariner-based spacecraft, launched since Voyager, included the Magellan probe to Venus, and the Galileo probe to Jupiter. A second-generation Mariner spacecraft, called the Mariner Mark II series, eventually evolved into the Cassini–Huygens probe, the total cost of the Mariner program was approximately $554 million. Mariner 2 was based on the Ranger Lunar probe, all of the Mariners launched after Mariner 2 had four solar panels for power, except for Mariner 10, which had two. Additionally, all except Mariner 1, Mariner 2 and Mariner 5 had TV cameras, the first five Mariners were launched on Atlas-Agena rockets, while the last five used the Atlas-Centaur. All Mariner-based probes after Mariner 10 used the Titan IIIE, Titan IV unmanned rockets or the Space Shuttle with a solid-fueled Inertial Upper Stage and multiple planetary flybys. Mariners, Mariner 1 Mariner 2 Mariner 3 Mariner 4 Mariner 5 Mariner 6 Mariner 7 Mariner 8 Mariner 9 Mariner 10 Mariner 1, a secondary objective was to make interplanetary magnetic field and/or particle measurements on the way to, and in the vicinity of, Venus. Mariner 1 was launched on July 22,1962, but was destroyed approximately 5 minutes after liftoff by the Air Force Range Safety Officer when its malfunctioning Atlas-Agena rocket went off course. Mariner 2 was launched on August 27,1962, sending it on a 3½-month flight to Venus, the mission was a success, and Mariner 2 became the first spacecraft to have flown by another planet. Mariner 2 – Defunct after successful mission, occupies a heliocentric orbit, sisterships Mariner 3 and Mariner 4 were Mars flyby missions. Mariner 3 was lost when the vehicles nose fairing failed to jettison. Mariner 4, launched on November 28,1964, was the first successful flyby of the planet Mars, Mariner 4 – Communications lost after bombardment by micrometeoroids. The Mariner 5 spacecraft was launched to Venus on June 14,1967, Mariners 6 and 7 were identical teammates in a two-spacecraft mission to Mars. Mariner 6 was launched on February 24,1969, followed by Mariner 7 on March 21,1969 and they flew over the equator and southern hemisphere of the planet Mars. Mariner 8 and Mariner 9 were identical sister craft designed to map the Martian surface simultaneously and its identical sister craft, Mariner 9, was launched in May 1971 and became the first artificial satellite of Mars. It entered Martian orbit in November 1971 and began photographing the surface and analyzing the atmosphere with its infrared, in Areocentric orbit until at least 2022 when it is projected to fall out of orbit and into the Martian atmosphere. It was also the first spacecraft to encounter two planets at close range, and for 33 years the spacecraft to photograph Mercury in closeup. Mission, plasma, charged particles, magnetic fields, radio occultation and celestial mechanics Status, Mariner Jupiter-Saturn was approved in 1972 after the cancellation of the Grand Tour program, which proposed visiting all the outer planets with multiple spacecraft
24.
Directional antenna
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A directional antenna or beam antenna is an antenna which radiates or receives greater power in specific directions allowing for increased performance and reduced interference from unwanted sources. Directional antennas provide increased performance over dipole antennas – or omnidirectional antennas in general – when greater concentration of radiation in a direction is desired. A high-gain antenna is an antenna with a focused, narrow radiowave beam width. This narrow beam allows more precise targeting of the radio signals. Most commonly referred to during space missions, these antennas are also in use all over Earth, most successfully in flat, open areas where no mountains lie to disrupt radiowaves. Low gain antennas are used in spacecraft as a backup to the high-gain antenna. The most common types are the Yagi antenna, the antenna, and the corner reflector antenna. Cellular repeaters often make use of directional antennas to give a far greater signal than can be obtained on a standard cell phone. Satellite Television receivers usually use parabolic antennas, for long and medium wavelength frequencies, tower arrays are used in most cases as directional antennas. When transmitting, a high-gain antenna allows more of the power to be sent in the direction of the receiver. When receiving, a high gain antenna captures more of the signal, as a consequence of their directivity, directional antennas also send less signal from directions other than the main beam. This property may be used to reduce interference, there are many ways to make a high-gain antenna - the most common are parabolic antennas, helical antennas, yagi antennas, and phased arrays of smaller antennas of any kind. Horn antennas can also be constructed with high gain, but are commonly seen. Still other configurations are possible - the Arecibo Observatory uses a combination of a line feed with a spherical reflector. Antenna gain is often quoted with respect to an antenna that radiates equally in all directions. This gain, when measured in decibels, is called dBi, conservation of energy dictates that high gain antennas must have narrow beams. For example, if a high gain antenna makes a 1 watt transmitter look like a 100 watt transmitter, in turn this implies that high-gain antennas must be physically large, since according to the diffraction limit, the narrower the beam desired, the larger the antenna must be. Antenna gain can also be measured in dBd, which is gain in Decibels compared to the maximum intensity direction of a half wave dipole
25.
Gyroscope
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A gyroscope is a spinning wheel or disc in which the axis of rotation is free to assume any orientation by itself. When rotating, the orientation of this axis is unaffected by tilting or rotation of the mounting, according to the conservation of angular momentum, because of this, gyroscopes are useful for measuring or maintaining orientation. Due to their precision, gyroscopes are used in gyrotheodolites to maintain direction in tunnel mining. Gyroscopes can be used to construct gyrocompasses, which complement or replace magnetic compasses, a gyroscope is a wheel mounted in two or three gimbals, which are a pivoted supports that allow the rotation of the wheel about a single axis. In the case of a gyroscope with two gimbals, the gimbal, which is the gyroscope frame, is mounted so as to pivot about an axis in its own plane determined by the support. This outer gimbal possesses one degree of freedom and its axis possesses none. The inner gimbal is mounted in the frame so as to pivot about an axis in its own plane that is always perpendicular to the pivotal axis of the gyroscope frame. This inner gimbal has two degrees of rotational freedom, the axle of the spinning wheel defines the spin axis. The rotor is constrained to spin about an axis, which is perpendicular to the axis of the inner gimbal. So the rotor possesses three degrees of freedom and its axis possesses two. The wheel responds to a force applied to the axis by a reaction force to the output axis. The behaviour of a gyroscope can be most easily appreciated by consideration of the front wheel of a bicycle. If the wheel is leaned away from the vertical so that the top of the moves to the left. In other words, rotation on one axis of the turning wheel produces rotation of the third axis, a gyroscope flywheel will roll or resist about the output axis depending upon whether the output gimbals are of a free or fixed configuration. Examples of some free-output-gimbal devices would be the attitude reference gyroscopes used to sense or measure the pitch, roll, the centre of gravity of the rotor can be in a fixed position. Some gyroscopes have mechanical equivalents substituted for one or more of the elements, for example, the spinning rotor may be suspended in a fluid, instead of being pivotally mounted in gimbals. In some special cases, the outer gimbal may be omitted so that the rotor has two degrees of freedom. Essentially, a gyroscope is a top combined with a pair of gimbals, Tops were invented in many different civilizations, including classical Greece, Rome, and China
26.
Attitude control
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Attitude control is controlling the orientation of an object with respect to an inertial frame of reference or another entity. The integrated field that studies the combination of sensors, actuators and algorithms is called Guidance, Navigation, a spacecrafts attitude must typically be stabilized and controlled for a variety of reasons. Propulsion system thrusters are fired only occasionally to make desired changes in spin rate, if desired, the spinning may be stopped through the use of thrusters or by yo-yo de-spin. The Pioneer 10 and Pioneer 11 probes in the solar system are examples of spin-stabilized spacecraft. Three-axis stabilization is a method of spacecraft attitude control in which the spacecraft is held fixed in the desired orientation without any rotation. One method is to use thrusters to continually nudge the spacecraft back. Thrusters may also be referred to as control systems, or reaction control systems. The space probes Voyager 1 and Voyager 2 employ this method, another method for achieving three-axis stabilization is to use electrically powered reaction wheels, also called momentum wheels, which are mounted on three orthogonal axes aboard the spacecraft. They provide a means to trade angular momentum back and forth between spacecraft and wheels, to rotate the vehicle on a given axis, the reaction wheel on that axis is accelerated in the opposite direction. To rotate the back, the wheel is slowed. This is done during maneuvers called momentum desaturation or momentum unload maneuvers, most spacecraft use a system of thrusters to apply the torque for desaturation maneuvers. A different approach was used by the Hubble Space Telescope, which had sensitive optics that could be contaminated by thruster exhaust, there are advantages and disadvantages to both spin stabilization and three-axis stabilization. Many spacecraft have components that require articulation, Voyager and Galileo, for example, were designed with scan platforms for pointing optical instruments at their targets largely independently of spacecraft orientation. Many spacecraft, such as Mars orbiters, have solar panels that must track the Sun so they can provide power to the spacecraft. Cassinis main engine nozzles are steerable, knowing where to point a solar panel, or scan platform, or a nozzle — that is, how to articulate it—requires knowledge of the spacecrafts attitude. Because AACS keeps track of the attitude, the Suns location. It logically falls to one subsystem, then, to manage both attitude and articulation, the name AACS may even be carried over to a spacecraft even if it has no appendages to articulate. Many sensors generate outputs that reflect the rate of change in attitude and these require a known initial attitude, or external information to use them to determine attitude
27.
Planet
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The term planet is ancient, with ties to history, astrology, science, mythology, and religion. Several planets in the Solar System can be seen with the naked eye and these were regarded by many early cultures as divine, or as emissaries of deities. As scientific knowledge advanced, human perception of the planets changed, in 2006, the International Astronomical Union officially adopted a resolution defining planets within the Solar System. This definition is controversial because it excludes many objects of mass based on where or what they orbit. The planets were thought by Ptolemy to orbit Earth in deferent, at about the same time, by careful analysis of pre-telescopic observation data collected by Tycho Brahe, Johannes Kepler found the planets orbits were not circular but elliptical. As observational tools improved, astronomers saw that, like Earth, the planets rotated around tilted axes, and some shared such features as ice caps and seasons. Since the dawn of the Space Age, close observation by space probes has found that Earth and the planets share characteristics such as volcanism, hurricanes, tectonics. Planets are generally divided into two types, large low-density giant planets, and smaller rocky terrestrials. Under IAU definitions, there are eight planets in the Solar System, in order of increasing distance from the Sun, they are the four terrestrials, Mercury, Venus, Earth, and Mars, then the four giant planets, Jupiter, Saturn, Uranus, and Neptune. Six of the planets are orbited by one or more natural satellites, several thousands of planets around other stars have been discovered in the Milky Way. e. in the habitable zone. On December 20,2011, the Kepler Space Telescope team reported the discovery of the first Earth-sized extrasolar planets, Kepler-20e and Kepler-20f, orbiting a Sun-like star, Kepler-20. A2012 study, analyzing gravitational microlensing data, estimates an average of at least 1.6 bound planets for every star in the Milky Way, around one in five Sun-like stars is thought to have an Earth-sized planet in its habitable zone. The idea of planets has evolved over its history, from the lights of antiquity to the earthly objects of the scientific age. The concept has expanded to include not only in the Solar System. The ambiguities inherent in defining planets have led to much scientific controversy, the five classical planets, being visible to the naked eye, have been known since ancient times and have had a significant impact on mythology, religious cosmology, and ancient astronomy. In ancient times, astronomers noted how certain lights moved across the sky, as opposed to the fixed stars, ancient Greeks called these lights πλάνητες ἀστέρες or simply πλανῆται, from which todays word planet was derived. In ancient Greece, China, Babylon, and indeed all pre-modern civilizations, it was almost universally believed that Earth was the center of the Universe and that all the planets circled Earth. The first civilization known to have a theory of the planets were the Babylonians
28.
Communication system
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The components of a communications system serve a common purpose, are technically compatible, use common procedures, respond to controls, and operate in union. Telecommunications is a method of communication, a communications subsystem is a functional unit or operational assembly that is smaller than the larger assembly under consideration. An optical communication system is any form of telecommunication that uses light as the transmission medium, fiber-optic communication systems transmit information from one place to another by sending light through an optical fiber. The light forms a signal that is modulated to carry information. A radio communication system is composed of several communications subsystems that give exterior communications capabilities, power line communication systems operate by impressing a modulated carrier signal on power wires. Different types of powerline communications use different frequency bands, depending on the signal characteristics of the power wiring used. Since the power wiring system was intended for transmission of AC power. The propagation problem is a factor for each type of power line communications. Mail Gmail imo Snapchat Instagram A duplex communication system is a composed of two connected parties or devices which can communicate with one another in both directions. The term duplex is used when describing communication between two parties or devices, an Antenna is basically a small length of a qwert conductor that is used to radiate or receive electromagnetic waves. Several types of antenna are used in communication, examples of communications subsystems include the Defense Communications System. These systems are designed to integrate the cross-communication of messages between are variety of communication technologies. An Automatic call distributor is a system that automatically queues, assigns. This is used often in service, ordering by telephone. These types of sensors are called input transducers in modern analog, at the end of the circuit is an antenna, the point at which the signal is released as electromagnetic waves. A communication channel is simply referring to the medium by which a signal travels, there are two types of media by which electrical signals travel, i. e. guided and unguided. Guided media refers to any medium that can be directed from transmitter to receiver by means of connecting cables, in optical fiber communication, the medium is an optical fiber. Other guided media might include coaxial cables, telephone wire, twisted-pairs, the other type of media, unguided media, refers to any communication channel that creates space between the transmitter and receiver
29.
Diameter
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In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle, both definitions are also valid for the diameter of a sphere. In more modern usage, the length of a diameter is called the diameter. In this sense one speaks of the rather than a diameter, because all diameters of a circle or sphere have the same length. Both quantities can be calculated efficiently using rotating calipers, for a curve of constant width such as the Reuleaux triangle, the width and diameter are the same because all such pairs of parallel tangent lines have the same distance. For an ellipse, the terminology is different. A diameter of an ellipse is any chord passing through the midpoint of the ellipse, for example, conjugate diameters have the property that a tangent line to the ellipse at the endpoint of one of them is parallel to the other one. The longest diameter is called the major axis, the word diameter is derived from Greek διάμετρος, diameter of a circle, from διά, across, through and μέτρον, measure. It is often abbreviated DIA, dia, d, or ⌀, the definitions given above are only valid for circles, spheres and convex shapes. However, they are cases of a more general definition that is valid for any kind of n-dimensional convex or non-convex object. The diameter of a subset of a space is the least upper bound of the set of all distances between pairs of points in the subset. So, if A is the subset, the diameter is sup, if the distance function d is viewed here as having codomain R, this implies that the diameter of the empty set equals −∞. Some authors prefer to treat the empty set as a case, assigning it a diameter equal to 0. For any solid object or set of scattered points in n-dimensional Euclidean space, in medical parlance concerning a lesion or in geology concerning a rock, the diameter of an object is the supremum of the set of all distances between pairs of points in the object. In differential geometry, the diameter is an important global Riemannian invariant, the symbol or variable for diameter, ⌀, is similar in size and design to ø, the Latin small letter o with stroke. In Unicode it is defined as U+2300 ⌀ Diameter sign, on an Apple Macintosh, the diameter symbol can be entered via the character palette, where it can be found in the Technical Symbols category. The character will not display correctly, however, since many fonts do not include it. In many situations the letter ø is a substitute, which in Unicode is U+00F8 ø
30.
Radio wave
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Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies as high as 300 GHz to as low as 3 kHz, though some definitions describe waves above 1 or 3 GHz as microwaves, at 300 GHz, the corresponding wavelength is 1 mm, and at 3 kHz is 100 km. Like all other electromagnetic waves, they travel at the speed of light, naturally occurring radio waves are generated by lightning, or by astronomical objects. Radio waves are generated by radio transmitters and received by radio receivers, the radio spectrum is divided into a number of radio bands on the basis of frequency, allocated to different uses. Radio waves were first predicted by mathematical work done in 1867 by Scottish mathematical physicist James Clerk Maxwell, Maxwell noticed wavelike properties of light and similarities in electrical and magnetic observations. Radio waves were first used for communication in the mid 1890s by Guglielmo Marconi, different frequencies experience different combinations of these phenomena in the Earths atmosphere, making certain radio bands more useful for specific purposes than others. It does not necessarily require a cleared sight path, at lower frequencies radio waves can pass through buildings, foliage and this is the only method of propagation possible at microwave frequencies and above. On the surface of the Earth, line of propagation is limited by the visual horizon to about 40 miles. This is the used by cell phones, cordless phones, walkie-talkies, wireless networks, FM and television broadcasting. Indirect propagation, Radio waves can reach points beyond the line-of-sight by diffraction, diffraction allows a radio wave to bend around obstructions such as a building edge, a vehicle, or a turn in a hall. Radio waves also reflect from surfaces such as walls, floors, ceilings, vehicles and these effects are used in short range radio communication systems. Ground waves allow mediumwave and longwave broadcasting stations to have coverage areas beyond the horizon, the nonzero resistance of the earth absorbs energy from ground waves, so as they propagate the waves lose power and the wavefronts bend over at an angle to the surface. As frequency decreases, the decrease and the achievable range increases. Military very low frequency and extremely low frequency communication systems can communicate over most of the Earth, and with submarines hundreds of feet underwater. Tropospheric propagation, In the VHF and UHF bands, radio waves can travel somewhat beyond the horizon due to refraction in the troposphere. This is due to changes in the index of air with temperature and pressure. At times, radio waves can travel up to 500 -1000 km due to tropospheric ducting and these effects are variable and not as reliable as ionospheric propagation, below. So radio waves directed at an angle into the sky can return to Earth beyond the horizon, by using multiple skips communication at intercontinental distances can be achieved
31.
Magnetic storage
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Magnetic storage or magnetic recording is the storage of data on a magnetised medium. Magnetic storage uses different patterns of magnetisation in a material to store data and is a form of non-volatile memory. The information is accessed using one or more read/write heads, as of 2017, magnetic storage media, primarily hard disks, are widely used to store computer data as well as audio and video signals. In the field of computing, the magnetic storage is preferred and in the field of audio and video production. The distinction is less technical and more a matter of preference, other examples of magnetic storage media include floppy disks, magnetic recording tape, and magnetic stripes on credit cards. Magnetic storage in the form of wire recording—audio recording on a wire—was publicized by Oberlin Smith in the Sept 8,1888 issue of the Electrical World. Smith had previously filed a patent in September,1878 but found no opportunity to pursue the idea as his business was machine tools, the first publicly demonstrated magnetic recorder was invented by Valdemar Poulsen in 1898. Poulsens device recorded a signal on a wire wrapped around a drum, in 1928, Fritz Pfleumer developed the first magnetic tape recorder. Early magnetic storage devices were designed to record analog audio signals, computers and now most audio and video magnetic storage devices record digital data. In old computers, magnetic storage was used for primary storage in a form of magnetic drum, or core memory, core rope memory, thin film memory. Unlike modern computers, magnetic tape was often used for secondary storage. Information is written to and read from the medium as it moves past devices called read-and-write heads that operate very close over the magnetic surface. The read-and-write head is used to detect and modify the magnetisation of the material immediately under it, there are two magnetic polarities, each of which is used to represent either 0 or 1. The magnetic surface is divided into many small sub-micrometer-sized magnetic regions, referred to as magnetic domains. Due to the nature of the magnetic material each of these magnetic regions is composed of a few hundred magnetic grains. Magnetic grains are typically 10 nm in size and each form a single magnetic domain. Each magnetic region in total forms a magnetic dipole which generates a magnetic field, for reliable storage of data, the recording material needs to resist self-demagnetisation, which occurs when the magnetic domains repel each other. Magnetic domains written too densely together to a weakly magnetisable material will degrade over time due to rotation of the moment one or more domains to cancel out these forces
32.
MHW-RTG
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The Multihundred-Watt radioisotope thermoelectric generators is a type of US radioisotope thermoelectric generator developed for the Voyager spacecrafts, Voyager 1 and Voyager 2. Each RTG had a weight of 37.7 kg including about 4.5 kg of Pu-238. It uses 24 pressed plutonium-238 oxide spheres and provides heat to generate approximately 157 watts of electrical power initially - halving every 87.7 years. Each RTG generated about 2400 Watts of thermal power, conversion of the decay heat of the plutonium to electrical power used 312 silicon-germanium thermoelectric couples. The initial thermoelectric couple hot junction temperature was 1273 K with a junction temperature of 573 K. Each Voyager spacecraft has 3 RTGs, collectively, the RTGs supplied each Voyager spacecraft with 470 watts at launch. MHW-RTGs were used on the Lincoln Experimental Satellites 8 and 9, subsequent US spacecraft used the GPHS-RTG which used similar SiGe thermoelectic devices but a different packaging of the fuel. Another later RTG was the MMRTG Nuclear power in space
33.
Plutonium-238
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Plutonium-238 is a radioactive isotope of plutonium that has a half-life of 87.7 years. Plutonium-238 is a very powerful alpha emitter and this makes the plutonium-238 isotope suitable for usage in radioisotope thermoelectric generators and radioisotope heater units. One gram of 238Pu corresponds to 1/238 moles, which is 2. 53×1021 plutonium atoms, considering its half-life t1/2 =87.7 years we can calculate its activity as A = λ N = ln 2 t 1 /2 N =634 GBq. It is the number of 238Pu decays per second, each of the emitted alpha particles has kinetic energy 5.593 MeV or 8. 96×10-13 J which is quickly converted to heat when the particle decelerates in the material. Therefore each gram of 238Pu spontaneously generates 0.568 W of heat, Plutonium-238 was the first isotope of plutonium to be discovered. It was synthesized by Glenn Seaborg and associates in December,1940 by bombarding uranium-238 with deuterons, creating neptunium-238, Plutonium-238 decays to uranium-234 and then further along the radium series to lead-206. Plutonium-238 was produced by irradiating Neptunium-237, which is a by-product of the production of Plutonium-239 weapons-grade material, as produced by Savannah River in their weapons reactor, shut down in 1988, Plutonium-238 was mixed with about 16% Plutonium-239. The first application was its use in a weapons component made at Mound for the Weapons Design Agency Lawrence Livermore Laboratory, Mound was chosen for this work because of its experience in producing the Polonium-210 fueled Urchin initiator and its work with several heavy elements in a Reactor Fuels program. Two Mound scientists spent 1959 at LLL in joint development while the Special Metallurgical Building was constructed at Mound to house the project, meanwhile the first sample of Plutonium-238 came to Mound in 1959. The weapons project was planned for about 1 kg/year of Pu-238 over a 3-year period, but the Pu-238 component could not be produced to the specifications despite a 2 year effort beginning at Mound in mid-1961. A maximum effort was undertaken with 3 shifts a day,6 days a week, a loosening of the specifications resulted in productivity of about 3%, and production finally began in 1964. Capt. R. T. Carpenter had chosen Pu-238 as the fuel for the first RTG to be launched into space as auxiliary power for the Transit IV Navy navigational satellite, June 29,1961. As of January 21,1963, the decision had yet to be made as to what isotope would be used to fuel the large RTGs for NASA programs. Then early in 1964 Mound scientists developed a different method of fabricating the weapon component that resulted in an efficiency of around 98%. When it was recognized that the source would not remain intact through cremation. An addition to the Special Metallurgical building weapon component production facility was completed at the end of 1964 for Pu-238 heat source fuel fabrication, a temporary fuel production facility was also installed in the Research Building in 1969 for Transit fuel fabrication. Pu-238 makes up one or two percent, but it may be responsible for much of the short-term decay heat because of its short half-life relative to other plutonium isotopes. Reactor-grade plutonium is not useful for producing Pu-238 for RTGs because difficult isotopic separation would be needed, in both cases, the targets are subjected to a chemical treatment, including dissolution in nitric acid to extract the plutonium-238
34.
Electric power
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Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second, Electric power is usually produced by electric generators, but can also be supplied by sources such as electric batteries. It is usually supplied to businesses and homes by the power industry through an electric power grid. Electric power is sold by the kilowatt hour which is the product of power in kilowatts multiplied by running time in hours. Electric utilities measure power using an electricity meter, which keeps a total of the electric energy delivered to a customer. Electrical power provides a low form of energy and can be carried long distances and converted into other forms of energy such as motion. Electric power, like power, is the rate of doing work, measured in watts. The term wattage is used colloquially to mean electric power in watts, the potential energy of the charges due to the voltage between the terminals is converted to kinetic energy in the device. These devices are called passive components or loads, they consume electric power from the circuit, converting it to other forms of such as mechanical work, heat, light. Examples are electrical appliances, such as bulbs, electric motors. In alternating current circuits the direction of the voltage periodically reverses, devices in which this occurs are called active devices or power sources, such as electric generators and batteries. Some devices can be either a source or a load, depending on the voltage, for example, a rechargeable battery acts as a source when it provides power to a circuit, but as a load when it is connected to a battery charger and is being recharged. Since electric power can flow either into or out of a component, Electric power flowing out of a circuit into a component is arbitrarily defined to have a positive sign, while power flowing into a circuit from a component is defined to have a negative sign. Thus passive components have positive power consumption, while power sources have negative power consumption and this is called the passive sign convention. In alternating current circuits, energy storage such as inductance and capacitance may result in periodic reversals of the direction of energy flow. The portion of power flow that, averaged over a cycle of the AC waveform. That portion of power due to stored energy, that returns to the source in each cycle, is known as reactive power. Real power is represented as a vector and reactive power is represented as a vertical vector
35.
Half-life
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Half-life is the time required for a quantity to reduce to half its initial value. The term is used in nuclear physics to describe how quickly unstable atoms undergo. The term is used more generally to characterize any type of exponential or non-exponential decay. For example, the medical sciences refer to the biological half-life of drugs, the converse of half-life is doubling time. The original term, half-life period, dating to Ernest Rutherfords discovery of the principle in 1907, was shortened to half-life in the early 1950s. Rutherford applied the principle of a radioactive elements half-life to studies of age determination of rocks by measuring the period of radium to lead-206. Half-life is constant over the lifetime of an exponentially decaying quantity, the accompanying table shows the reduction of a quantity as a function of the number of half-lives elapsed. A half-life usually describes the decay of discrete entities, such as radioactive atoms, in that case, it does not work to use the definition that states half-life is the time required for exactly half of the entities to decay. For example, if there are 3 radioactive atoms with a half-life of one second, instead, the half-life is defined in terms of probability, Half-life is the time required for exactly half of the entities to decay on average. In other words, the probability of a radioactive atom decaying within its half-life is 50%, for example, the image on the right is a simulation of many identical atoms undergoing radioactive decay. Note that after one half-life there are not exactly one-half of the remaining, only approximately. Nevertheless, when there are many identical atoms decaying, the law of large numbers suggests that it is a good approximation to say that half of the atoms remain after one half-life. There are various simple exercises that demonstrate probabilistic decay, for example involving flipping coins or running a computer program. The three parameters t1⁄2, τ, and λ are all related in the following way. Amount approaches zero as t approaches infinity as expected, some quantities decay by two exponential-decay processes simultaneously. There is a half-life describing any exponential-decay process, for example, The current flowing through an RC circuit or RL circuit decays with a half-life of RCln or lnL/R, respectively. For this example, the half time might be used instead of half life. In a first-order chemical reaction, the half-life of the reactant is ln/λ, in radioactive decay, the half-life is the length of time after which there is a 50% chance that an atom will have undergone nuclear decay
36.
Silicon
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Silicon is a chemical element with symbol Si and atomic number 14. A hard and brittle crystalline solid with a metallic luster. It is a member of group 14 in the table, along with carbon above it and germanium, tin, lead. It is not very reactive, although more reactive than germanium, Silicon is the eighth most common element in the universe by mass, but very rarely occurs as the pure element in the Earths crust. It is most widely distributed in dusts, sands, planetoids, over 90% of the Earths crust is composed of silicate minerals, making silicon the second most abundant element in the Earths crust after oxygen. Most silicon is used commercially without being separated, and often with little processing of the natural minerals, such use includes industrial construction with clays, silica sand, and stone. Silicate is used in Portland cement for mortar and stucco, and mixed with sand and gravel to make concrete for walkways, foundations. Silicates are used in whiteware ceramics such as porcelain, and in traditional quartz-based soda-lime glass, Silicon compounds such as silicon carbide are used as abrasives and components of high-strength ceramics. Elemental silicon also has an impact on the modern world economy. Most free silicon is used in the refining, aluminium-casting. Silicon is the basis of the widely used synthetic polymers called silicones, Silicon is an essential element in biology, although only tiny traces are required by animals. However, various sea sponges and microorganisms, such as diatoms and radiolaria, silica is deposited in many plant tissues, such as in the bark and wood of Chrysobalanaceae and the silica cells and silicified trichomes of Cannabis sativa, horsetails and many grasses. Silicon is a solid at room temperature, with a point of 1,414 °C. Like water, it has a density in a liquid state than in a solid state and it expands when it freezes. With a relatively high conductivity of 149 W·m−1·K−1, silicon conducts heat well. In its crystalline form, pure silicon has a gray color, like germanium, silicon is rather strong, very brittle, and prone to chipping. Silicon, like carbon and germanium, crystallizes in a cubic crystal structure with a lattice spacing of 0.5430710 nm. The outer electron orbital of silicon, like that of carbon, has four valence electrons, the 1s, 2s, 2p and 3s subshells are completely filled while the 3p subshell contains two electrons out of a possible six
37.
Germanium
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Germanium is a chemical element with symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the group, chemically similar to its group neighbors tin. Pure germanium is a semiconductor with a similar to elemental silicon. Like silicon, germanium naturally reacts and forms complexes with oxygen in nature, unlike silicon, it is too reactive to be found naturally on Earth in the free state. Because it seldom appears in high concentration, germanium was discovered late in the history of chemistry. Germanium ranks near fiftieth in relative abundance of the elements in the Earths crust, in 1869, Dmitri Mendeleev predicted its existence and some of its properties from its position on his periodic table, and called the element ekasilicon. Nearly two decades later, in 1886, Clemens Winkler found the new element along with silver and sulfur, although the new element somewhat resembled arsenic and antimony in appearance, the combining ratios in compounds agreed with Mendeleevs predictions for a relative of silicon. Winkler named the element after his country, Germany, today, germanium is mined primarily from sphalerite, though germanium is also recovered commercially from silver, lead, and copper ores. Germanium metal is used as a semiconductor in transistors and various electronic devices. Historically, the first decade of semiconductor electronics was based entirely on germanium, today, the amount of germanium produced for semiconductor electronics is one fiftieth the amount of ultra-high purity silicon produced for the same. Presently, the end uses are fibre-optic systems, infrared optics, solar cell applications. Germanium compounds are used for polymerization catalysts and have most recently found use in the production of nanowires. This element forms a number of organometallic compounds, such as tetraethylgermane. Germanium is not thought to be an element for any living organism. Some complex organic compounds are being investigated as possible pharmaceuticals. Similar to silicon and aluminum, natural germanium compounds tend to be insoluble in water, however, synthetic soluble germanium salts are nephrotoxic, and synthetic chemically reactive germanium compounds with halogens and hydrogen are irritants and toxins. Because of its position in his Periodic Table, Mendeleev called it ekasilicon, in mid-1885, at a mine near Freiberg, Saxony, a new mineral was discovered and named argyrodite because of the high silver content. The chemist Clemens Winkler analyzed this new mineral, which proved to be a combination of silver, sulfur, Winkler was able to isolate the new element in 1886 and found it similar to antimony
38.
Thermocouple
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A thermocouple is an electrical device consisting of two dissimilar conductors forming electrical junctions at differing temperatures. A thermocouple produces a temperature-dependent voltage as a result of the effect. Thermocouples are a widely used type of temperature sensor, commercial thermocouples are inexpensive, interchangeable, are supplied with standard connectors, and can measure a wide range of temperatures. In contrast to most other methods of measurement, thermocouples are self powered. The main limitation with thermocouples is accuracy, system errors of less than one degree Celsius can be difficult to achieve, Thermocouples are widely used in science and industry, applications include temperature measurement for kilns, gas turbine exhaust, diesel engines, and other industrial processes. Thermocouples are also used in homes, offices and businesses as the sensors in thermostats. At the time Seebeck referred to this as thermo-magnetism, the magnetic field he observed was later shown to be due to thermo-electric current. In practical use, the voltage generated at a junction of two different types of wire is what is of interest as this can be used to measure temperature at very high. The magnitude of the voltage depends on the types of wire used, generally, the voltage is in the microvolt range and care must be taken to obtain a usable measurement. Although current flows very little, power can be generated by a thermocouple junction. Power generation using multiple thermocouples, as in a thermopile, is common, the standard configuration for thermocouple usage is shown in the figure. Briefly, the desired temperature Tsense is obtained using three inputs—the characteristic function E of the thermocouple, the measured voltage V, and the reference junctions temperature Tref, the solution to the equation E = V + E yields Tsense. These details are hidden from the user since the reference junction block, voltmeter. The Seebeck effect refers to an electromotive force whenever there is a gradient in a conductive material. The standard measurement configuration shown in the figure, shows four temperature regions and thus four voltage contributions, Change from T m e t e r to T r e f, Change from T r e f to T s e n s e, in the alumel wire. Change from T s e n s e to T r e f, Change from T r e f to T m e t e r, in the upper copper wire. The first and fourth contributions cancel out exactly, because these regions involve the same temperature change, as a result, T m e t e r does not influence the measured voltage. The second and third contributions do not cancel, as they involve different materials, an integral does not need to be performed for every temperature measurement
39.
Light
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Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to light, which is visible to the human eye and is responsible for the sense of sight. Visible light is defined as having wavelengths in the range of 400–700 nanometres, or 4.00 × 10−7 to 7.00 × 10−7 m. This wavelength means a range of roughly 430–750 terahertz. The main source of light on Earth is the Sun, sunlight provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them. This process of photosynthesis provides virtually all the used by living things. Historically, another important source of light for humans has been fire, with the development of electric lights and power systems, electric lighting has effectively replaced firelight. Some species of animals generate their own light, a process called bioluminescence, for example, fireflies use light to locate mates, and vampire squids use it to hide themselves from prey. Visible light, as all types of electromagnetic radiation, is experimentally found to always move at this speed in a vacuum. In physics, the term sometimes refers to electromagnetic radiation of any wavelength. In this sense, gamma rays, X-rays, microwaves and radio waves are also light, like all types of light, visible light is emitted and absorbed in tiny packets called photons and exhibits properties of both waves and particles. This property is referred to as the wave–particle duality, the study of light, known as optics, is an important research area in modern physics. Generally, EM radiation, or EMR, is classified by wavelength into radio, microwave, infrared, the behavior of EMR depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths, when EMR interacts with single atoms and molecules, its behavior depends on the amount of energy per quantum it carries. There exist animals that are sensitive to various types of infrared, infrared sensing in snakes depends on a kind of natural thermal imaging, in which tiny packets of cellular water are raised in temperature by the infrared radiation. EMR in this range causes molecular vibration and heating effects, which is how these animals detect it, above the range of visible light, ultraviolet light becomes invisible to humans, mostly because it is absorbed by the cornea below 360 nanometers and the internal lens below 400. Furthermore, the rods and cones located in the retina of the eye cannot detect the very short ultraviolet wavelengths and are in fact damaged by ultraviolet. Many animals with eyes that do not require lenses are able to detect ultraviolet, by quantum photon-absorption mechanisms, various sources define visible light as narrowly as 420 to 680 to as broadly as 380 to 800 nm
40.
Digital computer
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A computer is a device that can be instructed to carry out an arbitrary set of arithmetic or logical operations automatically. The ability of computers to follow a sequence of operations, called a program, such computers are used as control systems for a very wide variety of industrial and consumer devices. The Internet is run on computers and it millions of other computers. Since ancient times, simple manual devices like the abacus aided people in doing calculations, early in the Industrial Revolution, some mechanical devices were built to automate long tedious tasks, such as guiding patterns for looms. More sophisticated electrical machines did specialized analog calculations in the early 20th century, the first digital electronic calculating machines were developed during World War II. The speed, power, and versatility of computers has increased continuously and dramatically since then, conventionally, a modern computer consists of at least one processing element, typically a central processing unit, and some form of memory. The processing element carries out arithmetic and logical operations, and a sequencing, peripheral devices include input devices, output devices, and input/output devices that perform both functions. Peripheral devices allow information to be retrieved from an external source and this usage of the term referred to a person who carried out calculations or computations. The word continued with the same meaning until the middle of the 20th century, from the end of the 19th century the word began to take on its more familiar meaning, a machine that carries out computations. The Online Etymology Dictionary gives the first attested use of computer in the 1640s, one who calculates, the Online Etymology Dictionary states that the use of the term to mean calculating machine is from 1897. The Online Etymology Dictionary indicates that the use of the term. 1945 under this name, theoretical from 1937, as Turing machine, devices have been used to aid computation for thousands of years, mostly using one-to-one correspondence with fingers. The earliest counting device was probably a form of tally stick, later record keeping aids throughout the Fertile Crescent included calculi which represented counts of items, probably livestock or grains, sealed in hollow unbaked clay containers. The use of counting rods is one example, the abacus was initially used for arithmetic tasks. The Roman abacus was developed from used in Babylonia as early as 2400 BC. Since then, many forms of reckoning boards or tables have been invented. In a medieval European counting house, a checkered cloth would be placed on a table, the Antikythera mechanism is believed to be the earliest mechanical analog computer, according to Derek J. de Solla Price. It was designed to calculate astronomical positions and it was discovered in 1901 in the Antikythera wreck off the Greek island of Antikythera, between Kythera and Crete, and has been dated to circa 100 BC
41.
Automaton
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An automaton is a self-operating machine, or a machine or control mechanism designed to automatically follow a predetermined sequence of operations, or respond to predetermined instructions. Some automata, such as bellstrikers in mechanical clocks, are designed to give the illusion to the observer that they are operating under their own power. The word automaton is the latinization of the Greek αὐτόματον, automaton and this word was first used by Homer to describe automatic door opening, or automatic movement of wheeled tripods. The automata in the Hellenistic world were intended as tools, toys, religious idols and he had invented the worlds first cuckoo clock. Complex mechanical devices are known to have existed in Hellenistic Greece, though the surviving example is the Antikythera mechanism. However, the information gleaned from recent scans of the fragments indicate that it may have come from the colonies of Corinth in Sicily and its also said that when King Solomon stepped upon the throne, a mechanism was set in motion. As soon as he stepped upon the first step, a golden ox, on each side, the animals helped the King up until he was comfortably seated upon the throne. In ancient China, an account of automata is found in the Lie Zi text. Within it there is a description of an earlier encounter between King Mu of Zhou and a mechanical engineer known as Yan Shi, an artificer. The latter proudly presented the king with a life-size, human-shaped figure of his mechanical handiwork and it walked with rapid strides, moving its head up and down, so that anyone would have taken it for a live human being. The artificer touched its chin, and it began singing, perfectly in tune and he touched its hand, and it began posturing, keeping perfect time. And, indeed, it turned out to be only a construction of leather, wood, glue and lacquer, variously coloured white, black, red, other notable examples of automata include Archytass dove, mentioned by Aulus Gellius. The manufacturing tradition of automata continued in the Greek world well into the Middle Ages, similar automata in the throne room were described by Luitprands contemporary Constantine Porphyrogenitus, who later became emperor, in his book Περὶ τῆς Βασιλείου Τάξεως. In the mid-8th century, the first wind powered automata were built, statues that turned with the wind over the domes of the four gates, the public spectacle of wind-powered statues had its private counterpart in the Abbasid palaces where automata of various types were predominantly displayed. In 827, Caliph Al-Mamun had a silver and golden tree in his palace in Baghdad, there were metal birds that sang automatically on the swinging branches of this tree built by Muslim inventors and engineers. The Abbasid Caliph Al-Muqtadir also had a tree in his palace in Baghdad in 915, with birds on it flapping their wings. In the 9th century, the Banū Mūsā brothers invented an automatic flute player. Al-Jazari described complex programmable humanoid automata amongst other machines he designed and constructed in the Book of Knowledge of Ingenious Mechanical Devices in 1206 and his automaton was a boat with four automatic musicians that floated on a lake to entertain guests at royal drinking parties
42.
Viking program
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The Viking program consisted of a pair of American space probes sent to Mars, Viking 1 and Viking 2. Each spacecraft was composed of two parts, an orbiter designed to photograph the surface of Mars from orbit. The orbiters also served as communication relays for the landers once they touched down, the Viking program grew from NASAs earlier, even more ambitious, Voyager Mars program, which was not related to the successful Voyager deep space probes of the late 1970s. Viking 1 was launched on August 20,1975, and the craft, Viking 2, was launched on September 9,1975. Viking 1 entered Mars orbit on June 19,1976, with Viking 2 following suit on August 7, the Viking 1 lander touched down on the surface of Mars on July 20,1976, and was joined by the Viking 2 lander on September 3. The orbiters continued imaging and performing other operations from orbit while the landers deployed instruments on the surface. The project cost roughly 1 billion USD in 1970s dollars, equivalent to about 11 billion USD in 2016 dollars and it was highly successful and formed most of the body of knowledge about Mars through the late 1990s and early 2000s. Each orbiter, based on the earlier Mariner 9 spacecraft, was an octagon approximately 2.5 m across, the fully fueled orbiter-lander pair had a mass of 3527 kg. After separation and landing, the lander had a mass of about 600 kg, the total launch mass was 2328 kg, of which 1445 kg were propellant and attitude control gas. The eight faces of the structure were 0.4572 m high and were alternately 1.397 and 0.508 m wide. The overall height was 3.29 m from the attachment points on the bottom to the launch vehicle attachment points on top. There were 16 modular compartments,3 on each of the 4 long faces, four solar panel wings extended from the axis of the orbiter, the distance from tip to tip of two oppositely extended solar panels was 9.75 m. The main propulsion unit was mounted above the orbiter bus, propulsion was furnished by a bipropellant liquid-fueled rocket engine which could be gimballed up to 9 degrees. The engine was capable of 1,323 N thrust, translating to a change in velocity of 1480 m/s, attitude control was achieved by 12 small compressed-nitrogen jets. An acquisition Sun sensor, a cruise Sun sensor, a Canopus star tracker, two accelerometers were also on board. Communications were accomplished through a 20 W S-band transmitter and two 20 W TWTAs, an X band downlink was also added specifically for radio science and to conduct communications experiments. A two-axis steerable parabolic dish antenna with a diameter of approximately 1.5 m was attached at one edge of the base. Two tape recorders were each capable of storing 1280 megabits, a 381-MHz relay radio was also available
43.
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
44.
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
Media related to the Voyager spacecraft at Wikimedia Commons
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