1.
European Space Agency
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The European Space Agency is an intergovernmental organisation of 22 member states, dedicated to the exploration of space. Established in 1975 and headquartered in Paris, France, ESA has a staff of about 2,000. The main European launch vehicle Ariane 5 is operated through Arianespace with ESA sharing in the costs of launching, after World War II, many European scientists left Western Europe in order to work with the United States. The meeting was attended by representatives from eight countries, including Harrie Massey. The Western European nations decided to have two different agencies, one concerned with developing a system, ELDO, and the precursor of the European Space Agency. The latter was established on 20 March 1964 by an agreement signed on 14 June 1962, from 1968 to 1972, ESRO launched seven research satellites. ESA in its current form was founded with the ESA Convention in 1975, ESA has 10 founding member states, Belgium, Denmark, France, Germany, Italy, the Netherlands, Spain, Sweden, Switzerland and the United Kingdom. These signed the ESA Convention in 1975 and deposited the instruments of ratification by 1980, during this interval the agency functioned in a de facto fashion. ESA launched its first major scientific mission in 1975, Cos-B, ESA joined NASA in the IUE, the worlds first high-orbit telescope, which was launched in 1978 and operated very successfully for 18 years. A number of successful Earth-orbit projects followed, and in 1986 ESA began Giotto, its first deep-space mission, to study the comets Halley and Grigg–Skjellerup. Hipparcos, a mission, was launched in 1989 and in the 1990s SOHO, Ulysses. Recent scientific missions in co-operation with NASA include the Cassini–Huygens space probe, as the successor of ELDO, ESA has also constructed rockets for scientific and commercial payloads. Ariane 1, launched in 1979, brought mostly commercial payloads into orbit from 1984 onward, the successor launch vehicle of Ariane 5, the Ariane 6 is already in the definition stage and is envisioned to enter service in the 2020s. The beginning of the new millennium saw ESA become, along with agencies like NASA, JAXA, ISRO, CSA and Roscosmos, one of the major participants in scientific space research. Although ESA had relied on co-operation with NASA in previous decades, especially the 1990s, changed circumstances led to decisions to rely more on itself, a 2011 press issue thus stated, Russia is ESAs first partner in its efforts to ensure long-term access to space. ESA maintains its scientific and research projects mainly for astronomy-space missions such as Corot, launched on 27 December 2006 and this is the reason space exploration is an integral part of overall space activities. It has always been so, and it will be more important in the future. ESA describes its work in two overlapping ways, For the general public the various fields of work are described as Activities, Member states participate to varying degrees in the mandatory and optional space programmes
2.
NASA
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President Dwight D. Eisenhower established NASA in 1958 with a distinctly civilian orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29,1958, disestablishing NASAs predecessor, the new agency became operational on October 1,1958. Since that time, most US space exploration efforts have led by NASA, including the Apollo Moon landing missions, the Skylab space station. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle, the agency is also responsible for the Launch Services Program which provides oversight of launch operations and countdown management for unmanned NASA launches. NASA shares data with various national and international such as from the Greenhouse Gases Observing Satellite. Since 2011, NASA has been criticized for low cost efficiency, from 1946, the National Advisory Committee for Aeronautics had been experimenting with rocket planes such as the supersonic Bell X-1. In the early 1950s, there was challenge to launch a satellite for the International Geophysical Year. An effort for this was the American Project Vanguard, after the Soviet launch of the worlds first artificial satellite on October 4,1957, the attention of the United States turned toward its own fledgling space efforts. This led to an agreement that a new federal agency based on NACA was needed to conduct all non-military activity in space. The Advanced Research Projects Agency was created in February 1958 to develop technology for military application. On July 29,1958, Eisenhower signed the National Aeronautics and Space Act, a NASA seal was approved by President Eisenhower in 1959. Elements of the Army Ballistic Missile Agency and the United States Naval Research Laboratory were incorporated into NASA, earlier research efforts within the US Air Force and many of ARPAs early space programs were also transferred to NASA. In December 1958, NASA gained control of the Jet Propulsion Laboratory, NASA has conducted many manned and unmanned spaceflight programs throughout its history. Some missions include both manned and unmanned aspects, such as the Galileo probe, which was deployed by astronauts in Earth orbit before being sent unmanned to Jupiter, the experimental rocket-powered aircraft programs started by NACA were extended by NASA as support for manned spaceflight. This was followed by a space capsule program, and in turn by a two-man capsule program. This goal was met in 1969 by the Apollo program, however, reduction of the perceived threat and changing political priorities almost immediately caused the termination of most of these plans. NASA turned its attention to an Apollo-derived temporary space laboratory, to date, NASA has launched a total of 166 manned space missions on rockets, and thirteen X-15 rocket flights above the USAF definition of spaceflight altitude,260,000 feet. The X-15 was an NACA experimental rocket-powered hypersonic research aircraft, developed in conjunction with the US Air Force, the design featured a slender fuselage with fairings along the side containing fuel and early computerized control systems
3.
Atlas II
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Atlas II was a member of the Atlas family of launch vehicles, which evolved from the successful Atlas missile program of the 1950s. It was designed to launch payloads into low orbit, geosynchronous transfer orbit or geosynchronous orbit. The Atlas line was continued by the Atlas III, used between 2000 and 2005, and the Atlas V which is still in use, Atlas II provided higher performance than the earlier Atlas I by using engines with greater thrust and longer fuel tanks for both stages. LR-89 and RS-27 were replaced by the RS-56, derived from the RS-27, the total thrust capability of the Atlas II of 490,000 pounds force enabled the booster to lift payloads of 6,100 pounds into geosynchronous transfer orbit of 22,000 miles or more. Atlas II was the last Atlas to use a three engine, stage-and-a-half design, two of its three engines were jettisoned during ascent, but its fuel tanks and other elements were retained. The two booster engines, RS-56-OBAs, were integrated into a unit called the MA-5A and shared a common gas generator. They burned for 164 seconds before being jettisoned, the central sustainer engine, an RS-56-OSA, would burn for an additional 125 seconds. The Vernier engines on the first stage of the Atlas I were replaced by a hydrazine fueled roll control system and this series used an improved Centaur upper stage, the world’s first cryogenic propellant stage, to increase its payload capability. Atlas II also had lower-cost electronics, a flight computer and longer propellant tanks than its predecessor. The original Atlas II was based on the Atlas I and its predecessors and this version flew between 1991 and 1998. Atlas IIA was a designed to service the commercial launch market. The main improvement was the switch from the RL10A-3-3A to RL10A-4 engine on the Centaur upper stage, the IIA version flew between 1992 and 2002. Atlas IIAS was largely identical to IIA, but added four Castor 4A solid rocket boosters to increase performance and these boosters were ignited in pairs, with one pair igniting on the ground, and the second igniting in the air shortly after the first pair separated. The half-stage booster section would then drop off as usual, IIAS was used between 1993 and 2004, concurrently with IIA. Led by lead engineer Samuel Wagner, the Atlas II was crucial to the development of the United States space program. Atlas IIs were launched from Cape Canaveral Air Force Station, Fla. by the 45th Space Wing, the final West Coast Atlas II launch was accomplished December 2003 by the 30th Space Wing, Vandenberg AFB, California
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.
Spaceport Florida Launch Complex 36
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Launch Complex 36 —formerly known as Space Launch Complex 36 from 1997 to 2010—is a launch complex at Cape Canaveral Air Force Station in Brevard County, Florida. It was used for Atlas launches by NASA and the US Air Force from 1962 until 2005, Blue Origin has leased the launch site since 2015 in order to build a new launch site for launching Blues orbital rockets. Orbital launches are expected to begin from LC36 no earlier than 2020, historically, the complex consisted of two launch pads, SLC-36A and SLC-36B, and was the launch site for the Pioneer, Surveyor, and Mariner probes in the 1960s and 1970s. There were a total of 68 and 77 launches from pads 36A and 36B, respectively, the Atlas rockets launched from Complex 36 were subsequently replaced by the Atlas V launch vehicle which launches from Complex 41 at Cape Canaveral beginning in 2002. LC-36A was the scene of the biggest on-pad explosion in Cape history when Atlas-Centaur AC-5 fell back onto the pad on March 2,1965, the accident spurred NASA to complete work on LC-36B which had been abandoned when it was 90% finished. In March 2010, the USAF 45th Space Wing issued Real Property Licenses to Space Florida for Space Launch Complexes 36 and 46 at Cape Canaveral Air Force Station. Moon Express leased the pad in February 2015 from Space Florida as a development and test site for its commercial lunar operations, as of 2016, orbital launches are expected to begin from LC-36 no earlier than 2020. The legacy Atlas-Centaur umbilical towers of both pads were demolished in 2006, the mobile service towers were both demolished in controlled explosions on June 16,2007. Tower B was demolished at 13,59 GMT and tower A followed twelve minutes later at 14,11, on September 15,2015, Blue Origin announced it would use Launch Complex 36 for launches of its orbital launch vehicle later in the decade. As of 2015, the first Blue launch from LC36 was planned for before 2020, as of October 2015, the pad design and configuration was not yet known. Blue broke ground for the facility to initiate construction activity on the site in June 2016, the New Glenn will be a very large 7. 0-meter -diameter vehicle. The first stage will be powered by seven BE-4 methane/oxygen engines producing 17.1 meganewtons total thrust at launch, the first stage will be reusable and is designed to land vertically. List of Cape Canaveral and Merritt Island launch sites Patrick Air Force Base
6.
Lagrangian point
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The Lagrange points mark positions where the combined gravitational pull of the two large masses provides precisely the centrifugal force required to orbit with them. There are five points, labeled L1 to L5, all in the orbital plane of the two large bodies. The first three are on the line connecting the two bodies, the last two, L4 and L5, each form an equilateral triangle with the two large bodies. The two latter points are stable, which implies that objects can orbit around them in a coordinate system tied to the two large bodies. Several planets have satellites near their L4 and L5 points with respect to the Sun, the three collinear Lagrange points were discovered by Leonhard Euler a few years before Lagrange discovered the remaining two. In 1772, Joseph-Louis Lagrange published an Essay on the three-body problem, in the first chapter he considered the general three-body problem. From that, in the chapter, he demonstrated two special constant-pattern solutions, the collinear and the equilateral, for any three masses, with circular orbits. The five Lagrangian points are labeled and defined as follows, The L1 point lies on the line defined by the two large masses M1 and M2, and between them. It is the most intuitively understood of the Lagrangian points, the one where the attraction of M2 partially cancels M1s gravitational attraction. Explanation An object that orbits the Sun more closely than Earth would normally have an orbital period than Earth. If the object is directly between Earth and the Sun, then Earths gravity counteracts some of the Suns pull on the object, the closer to Earth the object is, the greater this effect is. At the L1 point, the period of the object becomes exactly equal to Earths orbital period. L1 is about 1.5 million kilometers from Earth, the L2 point lies on the line through the two large masses, beyond the smaller of the two. Here, the forces of the two large masses balance the centrifugal effect on a body at L2. Explanation On the opposite side of Earth from the Sun, the period of an object would normally be greater than that of Earth. The extra pull of Earths gravity decreases the orbital period of the object, like L1, L2 is about 1.5 million kilometers from Earth. The L3 point lies on the line defined by the two masses, beyond the larger of the two. Explanation L3 in the Sun–Earth system exists on the side of the Sun
7.
Apsis
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An apsis is an extreme point in an objects orbit. The word comes via Latin from Greek and is cognate with apse, for elliptic orbits about a larger body, there are two apsides, named with the prefixes peri- and ap-, or apo- added to a reference to the thing being orbited. For a body orbiting the Sun, the point of least distance is the perihelion, the terms become periastron and apastron when discussing orbits around other stars. For any satellite of Earth including the Moon the point of least distance is the perigee, for objects in Lunar orbit, the point of least distance is the pericynthion and the greatest distance the apocynthion. For any orbits around a center of mass, there are the terms pericenter and apocenter, periapsis and apoapsis are equivalent alternatives. A straight line connecting the pericenter and apocenter is the line of apsides and this is the major axis of the ellipse, its greatest diameter. For a two-body system the center of mass of the lies on this line at one of the two foci of the ellipse. When one body is larger than the other it may be taken to be at this focus. Historically, in systems, apsides were measured from the center of the Earth. In orbital mechanics, the apsis technically refers to the distance measured between the centers of mass of the central and orbiting body. However, in the case of spacecraft, the family of terms are used to refer to the orbital altitude of the spacecraft from the surface of the central body. The arithmetic mean of the two limiting distances is the length of the axis a. The geometric mean of the two distances is the length of the semi-minor axis b, the geometric mean of the two limiting speeds is −2 ε = μ a which is the speed of a body in a circular orbit whose radius is a. The words pericenter and apocenter are often seen, although periapsis/apoapsis are preferred in technical usage, various related terms are used for other celestial objects. The -gee, -helion and -astron and -galacticon forms are used in the astronomical literature when referring to the Earth, Sun, stars. The suffix -jove is occasionally used for Jupiter, while -saturnium has very rarely used in the last 50 years for Saturn. The -gee form is used as a generic closest approach to planet term instead of specifically applying to the Earth. During the Apollo program, the terms pericynthion and apocynthion were used when referring to the Moon, regarding black holes, the term peri/apomelasma was used by physicist Geoffrey A. Landis in 1998 before peri/aponigricon appeared in the scientific literature in 2002
8.
Cluster (spacecraft)
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The failure has become known as one of the most infamous and expensive software bugs in history. The failure resulted in a loss of more than US$370 million, Cluster consisted of four 1,200 kilograms cylindrical, spin-stabilised spacecraft, powered by 224 watt solar cells. The spacecraft were to have flown in a formation, and were intended to conduct research into the Earths magnetosphere. The satellites would have placed into highly elliptical orbits,17,200 by 120,600 kilometres. The Ariane 5 reused the inertial reference platform from the Ariane 4, pre-flight tests had never been performed on the inertial platform under simulated Ariane 5 flight conditions so the error was not discovered before launch. During the investigation, a simulated Ariane 5 flight was conducted on another inertial platform and it failed in exactly the same way as the actual flight units. The greater horizontal acceleration caused a data conversion from a 64-bit floating point number to a 16-bit signed integer value to overflow, efficiency considerations had omitted range checks for this particular variable, though conversions of other variables in the code were protected. The exception halted the reference platforms, resulting in the destruction of the flight, a rapid change of attitude occurred, which caused the launcher to disintegrate at 39 seconds after H0 due to aerodynamic forces. Ariane 5s inertial reference system is essentially the same as a system presently flying on Ariane 4, when taking this design decision, it was not analysed or fully understood which values this particular variable might assume when the alignment software was allowed to operate after lift-off. Ariane 5 has an initial acceleration and trajectory, which leads to a build-up of horizontal velocity five times more rapid than for Ariane 4. The higher horizontal velocity of Ariane 5 generated, within the 40-second timeframe, the purpose of the review process, which involves all major partners in the Ariane 5 programme, is to validate design decisions and to obtain flight qualification. In this process, the limitations of the alignment software were not fully analysed, the specification of the inertial reference system and the tests performed at equipment level did not specifically include the Ariane 5 trajectory data. Consequently, the realignment function was not tested under simulated Ariane 5 flight conditions, and it would have been technically feasible to include almost the entire inertial reference system in the overall system simulations which were performed. For a number of reasons it was decided to use the output of the inertial reference system. Had the system included, the failure could have been detected. These simulations have faithfully reproduced the chain of events leading to the failure of the reference systems. Following the failure, four replacement Cluster II satellites were built and these were launched in pairs aboard Soyuz-U/Fregat rockets in 2000. The subsequent automated analysis of the Ariane code was the first example of static code analysis by abstract interpretation
9.
Spacecraft
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A spacecraft is a vehicle, or machine designed to fly in outer space. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, space colonization, planetary exploration, on a sub-orbital spaceflight, a spacecraft enters space and then returns to the surface, without having gone into an orbit. For orbital spaceflights, spacecraft enter closed orbits around the Earth or around other celestial bodies, robotic spacecraft used to support scientific research are space probes. Robotic spacecraft that remain in orbit around a body are artificial satellites. Only a handful of interstellar probes, such as Pioneer 10 and 11, Voyager 1 and 2, orbital spacecraft may be recoverable or not. By method of reentry to Earth they may be divided in non-winged space capsules, Sputnik 1 was the first artificial satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957, the launch ushered in new political, military, technological, and scientific developments, while the Sputnik launch was a single event, it marked the start of the Space Age. Apart from its value as a technological first, Sputnik 1 also helped to identify the upper atmospheric layers density and it also provided data on radio-signal distribution in the ionosphere. Pressurized nitrogen in the satellites false body provided the first opportunity for meteoroid detection, Sputnik 1 was launched during the International Geophysical Year from Site No. 1/5, at the 5th Tyuratam range, in Kazakh SSR. The satellite travelled at 29,000 kilometers per hour, taking 96.2 minutes to complete an orbit and this altitude is called the Kármán line. In particular, in the 1940s there were several test launches of the V-2 rocket, as of 2016, only three nations have flown manned spacecraft, USSR/Russia, USA, and China. The first manned spacecraft was Vostok 1, which carried Soviet cosmonaut Yuri Gagarin into space in 1961, there were five other manned missions which used a Vostok spacecraft. The second manned spacecraft was named Freedom 7, and it performed a sub-orbital spaceflight in 1961 carrying American astronaut Alan Shepard to an altitude of just over 187 kilometers, there were five other manned missions using Mercury spacecraft. Other Soviet manned spacecraft include the Voskhod, Soyuz, flown unmanned as Zond/L1, L3, TKS, China developed, but did not fly Shuguang, and is currently using Shenzhou. Except for the shuttle, all of the recoverable manned orbital spacecraft were space capsules. Manned space capsules The International Space Station, manned since November 2000, is a joint venture between Russia, the United States, Canada and several other countries, some reusable vehicles have been designed only for manned spaceflight, and these are often called spaceplanes. The first example of such was the North American X-15 spaceplane, the first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19,1963. The first partially reusable spacecraft, a winged non-capsule, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarins flight
10.
Astrium
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Astrium was an aerospace manufacturer subsidiary of the European Aeronautic Defence and Space Company that provided civil and military space systems and services from 2006 to 2013. In 2012, Astrium had a turnover of €5.8 billion and 18,000 employees in France, Germany, the United Kingdom, Spain, Astrium was a member of Institute of Space, its Applications and Technologies. In late 2013 Astrium was merged with Cassidian, the division of EADS. EADS itself was reorganized as the Airbus Group, with three divisions that include Airbus, Airbus Defence and Space, and Airbus Helicopters, Astrium Satellites was one of the three business units of Astrium, a subsidiary of EADS. EADS Astrium Satellites employs around 8,348 people on nine sites in the United Kingdom, France, Germany, as of 15 October 2012, the CEO of Astrium is Eric Beranger who took over from Evert Dudok who became Astrium Services. Astrium was formed in 2000 by the merger of Matra Marconi Space with the division of DaimlerChrysler Aerospace AG. Henceforth Astrium was a joint venture between EADS and BAE Systems, on 16 June 2003 the minority shareholder, BAE Systems, sold its 25% share to EADS, making EADS the sole shareholder. Astrium became EADS Astrium Satellites and in a wider restructuring became the constituent of EADS Astrium. Also, Paradigm Secure Communications, initially created by Astrium in the frame of the Skynet 5 contract for the UK Ministry of Defence became the constituent of EADS SPACE Services. CASA Espacio became part of EADS Astrium on 1 January 2004, EADS Astrium is the sole shareholder of Infoterra Ltd. On 1 July 2006, the French subsidiary of EADS Astrium, EADS Astrium SAS, the name of the new company is Astrium SAS. Equivalent mergers have been achieved in 2006 in the other countries, the EADS group does not communicate about these mergers, excepted when required by the law, such as in contractual documents. EADS Astrium Space Transportation was formed in June 2003 from the Space Infrastructure division of Astrium, until July 2006 it was called EADS Space Transportation and was a fully owned subsidiary of EADS Space. In July 2006 the three subsidiaries of EADS Space were reintegrated into one company, EADS Astrium, of which EADS Astrium Space Transportation is a business division, currently 4397 employees work in the launcher segment. The Space Transportation company is the contractor for the Ariane 5 launcher, the Columbus Module of the International Space Station. It also builds launchers for the French nuclear missile program, such as the M51 SLBM and it joined the team led by Lockheed Martin for a bid on NASAs Crew Exploration Vehicle, being in charge of the crafts Mission Module. The team won a contract from NASA in June 2005, in 2005, EADS Astrium Space Transportation started a campaign in favour of a project called LIFE, for astronomy from the Moon surface. The company has facilities in France and in Germany, the facility in Germany is located in Bremen
11.
Lockheed Martin
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Lockheed Martin is an American global aerospace, defense, security and advanced technologies company with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995 and it is headquartered in Bethesda, Maryland, in the Washington, DC, area. Lockheed Martin employs 126,000 people worldwide, Marillyn Hewson is the current President and Chief Executive Officer. Lockheed Martin is one of the largest companies in the aerospace, defense, security and it is the worlds largest defense contractor based on revenue for fiscal year 2014. In 2013, 78% of Lockheed Martins revenues came from sales, it topped the list of US federal government contractors. In 2009 US government contracts accounted for $38.4 billion, foreign government contracts $5.8 billion, Lockheed Martin operates in five business segments, Aeronautics, Information Systems & Global Solutions, Missiles and Fire Control, Rotary and Mission Systems, and Space Systems. The company also invests in healthcare systems, renewable energy systems, intelligent energy distribution, merger talks between Lockheed Corporation and Martin Marietta began in March 1994, with the companies announcing their $10 billion planned merger on August 30,1994. The deal was finalized on March 15,1995, when the two companies approved the merger. The segments of the two companies not retained by the new company formed the basis for the present L-3 Communications, Lockheed Martin also later spun off the materials company Martin Marietta Materials. Both companies contributed important products to the new portfolio, Lockheed products included the Trident missile, P-3 Orion, F-16 Fighting Falcon, F-22 Raptor, C-130 Hercules, A-4AR Fightinghawk and the DSCS-3 satellite. Martin Marietta products included Titan rockets, Sandia National Laboratories, Space Shuttle External Tank, Viking 1 and Viking 2 landers, the Transfer Orbit Stage and various satellite models. On April 22,1996, Lockheed Martin completed the acquisition of Loral Corporations defense electronics and system integration businesses for $9.1 billion, the remainder of Loral became Loral Space & Communications. Lockheed Martin abandoned plans for a $8, the development of the spacecraft cost $193.1 million. In May 2001, Lockheed Martin sold Lockheed Martin Control Systems to BAE Systems, on November 27,2000, Lockheed completed the sale of its Aerospace Electronic Systems business to BAE Systems for $1.67 billion, a deal announced in July 2000. This group encompassed Sanders Associates, Fairchild Systems, and Lockheed Martin Space Electronics & Communications. In 2001, Lockheed Martin won the contract to build the F-35 Lightning II, in 2001, Lockheed Martin settled a nine–year investigation conducted by NASAs Office of Inspector General with the assistance of the Defense Contract Audit Agency. The company paid the United States government $7.1 million based on allegations that its predecessor, Lockheed Engineering Science Corporation, submitted false lease costs claims to NASA. On August 31,2006, Lockheed Martin won a $3.9 billion contract from NASA to design and build the CEV capsule, in 2009, NASA reduced the capsule crew requirements from the initial six seats to four for transport to the International Space Station
12.
Sun
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The Sun is the star at the center of the Solar System. It is a perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99. 86% of the total mass of the Solar System. About three quarters of the Suns mass consists of hydrogen, the rest is mostly helium, with smaller quantities of heavier elements, including oxygen, carbon, neon. The Sun is a G-type main-sequence star based on its spectral class and it formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into a disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core and it is thought that almost all stars form by this process. The Sun is roughly middle-aged, it has not changed dramatically for more than four billion years and it is calculated that the Sun will become sufficiently large enough to engulf the current orbits of Mercury, Venus, and probably Earth. The enormous effect of the Sun on Earth has been recognized since prehistoric times, the synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar, which is the predominant calendar in use today. The English proper name Sun developed from Old English sunne and may be related to south, all Germanic terms for the Sun stem from Proto-Germanic *sunnōn. The English weekday name Sunday stems from Old English and is ultimately a result of a Germanic interpretation of Latin dies solis, the Latin name for the Sun, Sol, is not common in general English language use, the adjectival form is the related word solar. The term sol is used by planetary astronomers to refer to the duration of a solar day on another planet. A mean Earth solar day is approximately 24 hours, whereas a mean Martian sol is 24 hours,39 minutes, and 35.244 seconds. From at least the 4th Dynasty of Ancient Egypt, the Sun was worshipped as the god Ra, portrayed as a falcon-headed divinity surmounted by the solar disk, and surrounded by a serpent. In the New Empire period, the Sun became identified with the dung beetle, in the form of the Sun disc Aten, the Sun had a brief resurgence during the Amarna Period when it again became the preeminent, if not only, divinity for the Pharaoh Akhenaton. The Sun is viewed as a goddess in Germanic paganism, Sól/Sunna, in ancient Roman culture, Sunday was the day of the Sun god. It was adopted as the Sabbath day by Christians who did not have a Jewish background, the symbol of light was a pagan device adopted by Christians, and perhaps the most important one that did not come from Jewish traditions
13.
Comet
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A comet is an icy small Solar System body that, when passing close to the Sun, warms and begins to evolve gasses, a process called outgassing. This produces an atmosphere or coma, and sometimes also a tail. These phenomena are due to the effects of radiation and the solar wind acting upon the nucleus of the comet. Comet nuclei range from a few hundred metres to tens of kilometres across and are composed of collections of ice, dust. The coma may be up to 15 times the Earths diameter, if sufficiently bright, a comet may be seen from the Earth without the aid of a telescope and may subtend an arc of 30° across the sky. Comets have been observed and recorded since ancient times by many cultures, Comets usually have highly eccentric elliptical orbits, and they have a wide range of orbital periods, ranging from several years to potentially several millions of years. Short-period comets originate in the Kuiper belt or its associated scattered disc, long-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside the Kuiper belt to halfway to the nearest star. Long-period comets are set in motion towards the Sun from the Oort cloud by gravitational perturbations caused by passing stars, hyperbolic comets may pass once through the inner Solar System before being flung to interstellar space. The appearance of a comet is called an apparition, Comets are distinguished from asteroids by the presence of an extended, gravitationally unbound atmosphere surrounding their central nucleus. This atmosphere has parts termed the coma and the tail, however, extinct comets that have passed close to the Sun many times have lost nearly all of their volatile ices and dust and may come to resemble small asteroids. Asteroids are thought to have a different origin from comets, having formed inside the orbit of Jupiter rather than in the outer Solar System, the discovery of main-belt comets and active centaur minor planets has blurred the distinction between asteroids and comets. As of November 2014 there are 5,253 known comets, however, this represents only a tiny fraction of the total potential comet population, as the reservoir of comet-like bodies in the outer Solar System is estimated to be one trillion. Roughly one comet per year is visible to the eye, though many of those are faint. Particularly bright examples are called Great Comets, the word comet derives from the Old English cometa from the Latin comēta or comētēs. That, in turn, is a latinisation of the Greek κομήτης, Κομήτης was derived from κομᾶν, which was itself derived from κόμη and was used to mean the tail of a comet. The astronomical symbol for comets is ☄, consisting of a disc with three hairlike extensions. The solid, core structure of a comet is known as the nucleus, cometary nuclei are composed of an amalgamation of rock, dust, water ice, and frozen gases such as carbon dioxide, carbon monoxide, methane, and ammonia. As such, they are described as dirty snowballs after Fred Whipples model
14.
Space
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Space is the boundless three-dimensional extent in which objects and events have relative position and direction. Physical space is conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum known as spacetime. The concept of space is considered to be of importance to an understanding of the physical universe. However, disagreement continues between philosophers over whether it is itself an entity, a relationship between entities, or part of a conceptual framework. Many of these classical philosophical questions were discussed in the Renaissance and then reformulated in the 17th century, in Isaac Newtons view, space was absolute—in the sense that it existed permanently and independently of whether there was any matter in the space. Other natural philosophers, notably Gottfried Leibniz, thought instead that space was in fact a collection of relations between objects, given by their distance and direction from one another. In the 18th century, the philosopher and theologian George Berkeley attempted to refute the visibility of spatial depth in his Essay Towards a New Theory of Vision. Kant referred to the experience of space in his Critique of Pure Reason as being a pure a priori form of intuition. In the 19th and 20th centuries mathematicians began to examine geometries that are non-Euclidean, in space is conceived as curved. According to Albert Einsteins theory of relativity, space around gravitational fields deviates from Euclidean space. Experimental tests of general relativity have confirmed that non-Euclidean geometries provide a model for the shape of space. In the seventeenth century, the philosophy of space and time emerged as an issue in epistemology. At its heart, Gottfried Leibniz, the German philosopher-mathematician, and Isaac Newton, unoccupied regions are those that could have objects in them, and thus spatial relations with other places. For Leibniz, then, space was an abstraction from the relations between individual entities or their possible locations and therefore could not be continuous but must be discrete. Space could be thought of in a way to the relations between family members. Although people in the family are related to one another, the relations do not exist independently of the people, but since there would be no observational way of telling these universes apart then, according to the identity of indiscernibles, there would be no real difference between them. According to the principle of sufficient reason, any theory of space that implied that there could be two possible universes must therefore be wrong. Newton took space to be more than relations between objects and based his position on observation and experimentation
15.
Space weather
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Space weather is distinct from the terrestrial weather of the Earths atmosphere. The science of space weather is focused on research and practical applications. The term space weather was first used in the 1950s and came into usage in the 1990s. For many centuries, the effects of weather were noticed. Displays of auroral light have long been observed at high latitudes, in 1724, George Graham reported that the needle of a magnetic compass was regularly deflected from magnetic north over the course of each day. In 1859, a magnetic storm caused brilliant auroral displays. Kristian Birkeland explained the physics of aurora by creating artificial aurora in his laboratory, the introduction of radio revealed that periods of extreme static or noise occurred. Severe radar jamming during a large event in 1942 led to the discovery of solar radio bursts. In the 20th century the interest in space weather expanded as military, communications satellites are a vital part of global commerce. Weather satellite systems provide information about terrestrial weather, the signals from satellites of the Global Positioning System are used in a wide variety of applications. Space weather phenomena can interfere with or damage these satellites or interfere with the signals with which they operate. Space weather phenomena can cause damaging surges in long distance transmission lines and expose passengers and crew of aircraft travel to radiation, the International Geophysical Year, increased research into space weather. In 1958, the Explorer I satellite discovered the Van Allen belts, in January 1959, the Soviet satellite Luna 1 first directly observed the solar wind and measured its strength. In 1969, INJUN-5 made the first direct observation of the electric field impressed on the Earths high latitude ionosphere by the solar wind, in the early 1970s, Triad data demonstrated that permanent electric currents flowed between the auroral oval and the magnetosphere. The term space weather came into usage in the 1990s along with the belief that spaces impact on human systems demanded a more coordinated research and application framework. The concept was turned into a plan in 2000, an implementation plan in 2002, an assessment in 2006. A revised action plan was scheduled to be released in 2011 followed by an implementation plan in 2012. One part of the National Space Weather Program is to show users that space weather affects their business, private companies now acknowledge space weather is a real risk for todays businesses
16.
WIND (spacecraft)
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Wind was designed and manufactured by Martin Marietta Astro Space Division in East Windsor, New Jersey. The satellite is a spin stabilized cylindrical satellite with a diameter of 2.4 m and it was deployed to study radio waves and plasma that occur in the solar wind and in the Earths magnetosphere. Wind has been at L1 continuously since 2004, and is operating as of 5 April 2017. Wind currently has enough fuel to last over 50 years at L1, Wind continues to produce new and exciting scientific results and as of January 31,2017 has accumulated over 4310 refereed scientific publications. Mission operations are conducted from the Multi-Mission Operations Center in Building 14 at Goddard Space Flight Center in Greenbelt, Wind data can be accessed using the SPEDAS software. Wind is the ship to GGS Polar. Provide complete plasma, energetic particle, and magnetic field input for magnetospheric and ionospheric studies, determine the magnetospheric output to interplanetary space in the up-stream region. Investigate basic plasma processes occurring in the solar wind. Provide baseline ecliptic plane observations to be used in heliospheric latitudes from ULYSSES, the aim of ISTP is to understand the behavior of the solar-terrestrial plasma environment in order to predict how the Earths atmosphere will respond to changes in solar wind conditions. Winds objective is to measure the properties of the wind before it reaches the Earth. The Konus and TGRS instruments are primarily for gamma-ray and high energy photon observations of flares or gamma-ray bursts. The SMS experiment measures the mass and mass-to-charge ratios of heavy ions, the SWE and 3DP experiments are meant to measure/analyze the lower energy solar wind protons and electrons. The WAVES and MFI experiments were designed to measure the electric and magnetic fields observed in the solar wind, all together, the Wind spacecrafts suite of instruments allows for a complete description of plasma phenomena in the solar wind plane of the ecliptic. The electric field detectors of the Wind WAVES instrument are composed of three electric field dipole antennas, two in the spin plane of the spacecraft and one along the spin axis. The longer of the two spin plane antenna, defined as Ex, is 100 m tip-to-tip while the shorter, the spin axis dipole, defined as Ez, is roughly 12 m tip-to-tip. When accounting for spacecraft potential, these lengths are adjusted to ~41.1 m, ~3.79 m. The Wind WAVES instrument also detects magnetic fields using three orthogonal search coil magnetometers, the XY search coils are oriented to be parallel to the XY dipole antenna. The search coils allow for high-frequency magnetic field measurements, the WAVES Z-Axis is anti-parallel to Z-GSE direction
17.
Advanced Composition Explorer
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Real-time data from ACE is used by the NOAA Space Weather Prediction Center to improve forecasts and warnings of solar storms. The ACE robotic spacecraft was launched August 25,1997 and entered a Lissajous orbit close to the L1 Lagrangian point on December 12,1997, the spacecraft is currently operating at that orbit. Because ACE is in an orbit, and has regular station-keeping maneuvers. The spacecraft is still in good condition in 2015, and is projected to have enough fuel to maintain its orbit until 2024. NASA Goddard Space Flight Center managed the development and integration of the ACE spacecraft and these observations have been used to, Generate a set of solar isotopic abundances based on direct sampling of solar material. Determine the coronal elemental and isotopic composition with greatly improved accuracy, establish the pattern of isotopic differences between galactic cosmic ray and solar system matter. Measure the elemental and isotopic abundances of interstellar and interplanetary “pick–up ions”, determine the isotopic composition of the “anomalous cosmic ray component”, which represents a sample of the local interstellar medium. Isotopic “anomalies” in meteorites indicate that the system was not homogeneous when formed. Similarly, the Galaxy is neither uniform in space nor constant in time due to stellar nucleosynthesis. ACE measurements have been used to, Search for differences between the composition of solar and meteoritic material. Determine the contributions of solar–wind and solar energetic particles to lunar and meteoritic material, determine the dominant nucleosynthetic processes that contribute to cosmic ray source material. Determine whether cosmic rays are a sample of freshly synthesized material or of the interstellar medium. Search for isotopic patterns in solar and Galactic material as a test of galactic evolution models, the detailed composition and charge–state data provided by ACE are used to, Isolate the dominant coronal formation processes by comparing a broad range of coronal and photospheric abundances. Study plasma conditions at the source of wind and solar energetic particles by measuring and comparing the charge states of these two populations. Study solar wind acceleration processes and any charge or mass–dependent fractionation in various types of solar wind flows, particle acceleration is ubiquitous in nature and understanding its nature is one of the fundamental problems of space plasma astrophysics. Constrain solar flare, coronal shock, and interplanetary shock acceleration models with charge, mass, test theoretical models for 3He–rich flares and solar γ–ray events. The nuclei detected in this interval are predominantly cosmic rays originating in our Galaxy. The instrument has a factor of 250 cm2 sr for isotope measurements
18.
Deep Space Climate Observatory
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Deep Space Climate Observatory is a NOAA Earth observation and space weather satellite launched by SpaceX on a Falcon 9 launch vehicle on February 11,2015 from Cape Canaveral. It was originally developed as a NASA satellite proposed in 1998 by then-Vice President Al Gore for the purpose of Earth observation, at this location it has a continuous view of the Sun and the sunlit side of the Earth. The satellite is orbiting the Sun-Earth L1 point in a six-month period and it takes full-Earth pictures about every two hours and is able to process them faster than other Earth observation satellites. DSCOVR started orbiting around L1 by June 8,2015, just over 100 days after launch, after the spacecraft arrived on site and entered its operational phase, NASA began releasing near-real time images of Earth through the EPIC instruments website. Gore hoped not only to science with these images, but also to raise awareness of the Earth itself. In addition to a camera, a radiometer would take the first direct measurements of how much sunlight is reflected and emitted from the whole Earth. This data could constitute a barometer for the process of global warming, the Bush Administration put the project on hold shortly after George W. Bushs inauguration. Members of the U. S. Congress asked the National Academy of Sciences whether the project was worthwhile, the resulting report, released March 2000, stated that the mission was strong and scientifically vital. Triana was removed from its original launch opportunity on STS-107, the $100 million satellite remained in storage for the duration of the Bush administration. In November 2008 the satellite was removed from storage and began recertification for a launch on board a Delta II or a Falcon 9. Al Gore used part of his book Our Choice as an attempt to revive debate on the DSCOVR payload, the book mentions legislative efforts by Senators Barbara Mikulski and Bill Nelson to get the satellite launched. NASA renamed the satellite Deep Space Climate Observatory, in an attempt to support for the project. In February 2011, the Obama administration attempted to secure funding to re-purpose the DSCOVR spacecraft as an observatory to replace the aging Advanced Composition Explorer spacecraft. In September 2013 NASA cleared DSCOVR to proceed to the implementation phase targeting an early 2015 launch, NASA Goddard Space Flight Center is providing management and systems engineering to the mission. DSCOVR is built on the SMEX-Lite spacecraft bus, and has a mass of approximately 570 kg. The main science instrument sets are the Sun-observing Plasma Magnetometer and the Earth-observing NIST Advanced Radiometer, DSCOVR has two deployable solar arrays, a propulsion module, boom, and antenna. The Plasma-Magnetometer measures solar wind for space weather predictions and it has three instruments, Magnetometer measures magnetic field. Faraday cup measures positively charged particles, the Earth Polychromatic Imaging Camera takes images of the sunlit side of Earth for various Earth sciences purposes, in 10 different channels from ultraviolet to near infrared
19.
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
20.
Astronomical unit
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The astronomical unit is a unit of length, roughly the distance from Earth to the Sun. However, that varies as Earth orbits the Sun, from a maximum to a minimum. Originally conceived as the average of Earths aphelion and perihelion, it is now defined as exactly 149597870700 metres, the astronomical unit is used primarily as a convenient yardstick for measuring distances within the Solar System or around other stars. However, it is also a component in the definition of another unit of astronomical length. A variety of symbols and abbreviations have been in use for the astronomical unit. In a 1976 resolution, the International Astronomical Union used the symbol A for the astronomical unit, in 2006, the International Bureau of Weights and Measures recommended ua as the symbol for the unit. In 2012, the IAU, noting that various symbols are presently in use for the astronomical unit, in the 2014 revision of the SI Brochure, the BIPM used the unit symbol au. In ISO 80000-3, the symbol of the unit is ua. Earths orbit around the Sun is an ellipse, the semi-major axis of this ellipse is defined to be half of the straight line segment that joins the aphelion and perihelion. The centre of the sun lies on this line segment. In addition, it mapped out exactly the largest straight-line distance that Earth traverses over the course of a year, knowing Earths shift and a stars shift enabled the stars distance to be calculated. But all measurements are subject to some degree of error or uncertainty, improvements in precision have always been a key to improving astronomical understanding. Improving measurements were continually checked and cross-checked by means of our understanding of the laws of celestial mechanics, the expected positions and distances of objects at an established time are calculated from these laws, and assembled into a collection of data called an ephemeris. NASAs Jet Propulsion Laboratory provides one of several ephemeris computation services, in 1976, in order to establish a yet more precise measure for the astronomical unit, the IAU formally adopted a new definition. Equivalently, by definition, one AU is the radius of an unperturbed circular Newtonian orbit about the sun of a particle having infinitesimal mass. As with all measurements, these rely on measuring the time taken for photons to be reflected from an object. However, for precision the calculations require adjustment for such as the motions of the probe. In addition, the measurement of the time itself must be translated to a scale that accounts for relativistic time dilation
21.
Reaction wheel
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A reaction wheel is a type of flywheel used primarily by spacecraft for attitude control without using fuel for rockets or other reaction devices. They are particularly useful when the spacecraft must be rotated by very small amounts and they may also reduce the mass fraction needed for fuel. Reaction wheels can rotate a spacecraft only around its center of mass, Reaction wheels work around a nominal zero rotation speed. However, external torques on the spacecraft may require a gradual buildup of reaction wheel rotation speed to maintain the spacecraft in a fixed orientation. A reaction wheel is sometimes operated as a wheel, by operating it at a constant rotation speed. This has the effect of tending to stabilize that spacecraft axis to point in a nearly-fixed direction, a control moment gyroscope is a related but different type of attitude actuator, generally consisting of a momentum wheel mounted in a one-axis or two-axis gimbal. Changes in speed are controlled electronically by computer, the strength of the materials used in a reaction wheel determine the speed at which the wheel would come apart, and therefore how much angular momentum it can store. Since the reaction wheel is a fraction of the spacecrafts total mass, easily controlled. The wheels therefore permit very precise changes in a spacecrafts attitude, for this reason, reaction wheels are often used to aim spacecraft carrying cameras or telescopes. Over time, reaction wheels may build up stored momentum that needs to be cancelled, designers therefore supplement reaction wheel systems with other attitude control mechanisms. In the presence of a field, a spacecraft can employ magnetorquers to transfer angular momentum to the Earth through its planetary magnetic field. Most spacecraft, however, also need fast pointing, and cannot afford the extra mass of three control systems. Designers therefore usually use conventional monopropellant vernier engines for all these purposes, the failure of one or more reaction wheels can cause a spacecraft to lose its ability to maintain position and thus potentially cause a mission failure. Two servicing missions to the Hubble Space Telescope have replaced a reaction wheel, in February 1997, the Second Servicing Mission replaced one after electrical anomalies, rather than any mechanical problem. Study of the mechanism provided a rare opportunity to study equipment that had undergone long-term service in space. This was found to be in excellent condition, in 2002, Servicing Mission 3B, astronauts from the shuttle Columbia replaced another reaction wheel. Neither of these wheels had failed and Hubble was designed with four redundant wheels, in 2004, during the mission of the Hayabusa spacecraft, an X-axis reaction wheel failed. The Y-axis wheel failed in 2005, causing the craft to rely on chemical thrusters to maintain attitude control, from July 2012 to May 11,2013, two out of the four reaction wheels in the Kepler telescope failed
22.
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
23.
Chromosphere
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The chromosphere is the second of the three main layers in the Suns atmosphere and is roughly 3,000 to 5,000 kilometers deep. The chromospheres rosy red color is apparent during eclipses. The Chromosphere sits just above the photosphere and below the transition region. The layer of the chromosphere atop the photosphere is homogeneous, a forest of hairy appearing spicules rise from the homogeneous layer some of which extend 10,000 km into the corona above. The density of the chromosphere is only 10−4 times that of the photosphere, the layer beneath and this makes the chromosphere normally invisible and it can be seen only during a total eclipse, where its reddish color is revealed. The color hues are anywhere between pink and red, however, without special equipment, the chromosphere cannot normally be seen due to the overwhelming brightness of the photosphere beneath. The density of the chromosphere decreases with distance from the center of the Sun and this decreases logarithmically from 1017 particles per cubic centimeter, or approximately 2×10−4 kg/m3 to under 1. 6×10−11 kg/m3 at the outer boundary. Chromospheres have been observed also in other than the Sun. Whilst the photosphere has a line spectrum, the chromospheres spectrum is dominated by emission lines. In particular, one of its strongest lines is the Hα at a wavelength of 656.3 nm, a wavelength of 656.3 nm is in the red part of the spectrum, which causes the chromosphere to have its characteristic reddish colour. By analysing the spectrum of the chromosphere, it was found that the temperature of this layer of the atmosphere increases with increasing height in the chromosphere itself. The temperature at the top of photosphere is only about 4,400 K, while at the top of chromosphere, some 2,000 km higher and this is however the opposite of what we find in the photosphere, where the temperature drops with increasing height. It is not yet fully understood what causes the temperature of the chromosphere to paradoxically increase further from the Suns interior. However, it likely to be explained, partially or totally. Solar prominences rise up through the chromosphere from the photosphere, sometimes reaching altitudes of 150,000 km and these gigantic plumes of gas are the most spectacular of solar phenomena, aside from the less frequent solar flares. The most common feature is the presence of spicules, long fingers of luminous gas which appear like the blades of a huge field of fiery grass growing upwards from the photosphere below. Spicules rise to the top of the chromosphere and then back down again over the course of about 10 minutes. Similarly, there are horizontal wisps of gas called fibrils, which last about twice as long as spicules, images taken in typical chromospheric lines show the presence of bright cells, usually called as network, while the surrounding black regions are named internetwork
24.
Solar transition region
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The solar transition region is a region of the Suns atmosphere, between the chromosphere and corona. It is visible from space using telescopes that can sense ultraviolet, below, most of the helium is not fully ionized, so that it radiates energy very effectively, above, it becomes fully ionized. This has an effect on the equilibrium temperature. This makes radiative transfer of energy within the region very complicated. The transition region itself is not well studied in part because of the computational cost, uniqueness and this condition holds at the top of the chromosphere, where the equilibrium temperature is a few tens of thousands of kelvins. Applying slightly more heat causes the helium to ionize fully, at which point it ceases to couple well to the Lyman continuum, the temperature jumps up rapidly to nearly one million kelvin, the temperature of the solar corona. The transition region consists of material at or around this temperature catastrophe, the transition region is visible in far-ultraviolet images from the TRACE spacecraft, as a faint nimbus above the dark surface of the Sun and the corona. The nimbus also surrounds FUV-dark features such as solar prominences, which consist of condensed material that is suspended at coronal altitudes by the magnetic field, moreton wave Coronal hole Spicule Animated explanation of the Transition Region. Animated explanation of the temperature of the Transition Region
25.
Corona
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A corona is an aura of plasma that surrounds the sun and other stars. The Suns corona extends millions of kilometres into space and is most easily seen during a solar eclipse. The word corona is a Latin word meaning crown, from the Ancient Greek κορώνη, the high temperature of the Suns corona gives it unusual spectral features, which led some in the 19th century to suggest that it contained a previously unknown element, coronium. Instead, these features have since been explained by highly ionized iron. Bengt Edlén, following the work of Grotrian, first identified the coronal spectral lines in 1940 as transitions from low-lying metastable levels of the configuration of highly ionised metals. These high stages of ionisation indicate a temperature in excess of 1,000,000 kelvins. Light from the corona comes from three sources, from the same volume of space. The suns corona is much hotter than the surface of the Sun. The corona is 10−12 times as dense as the photosphere, the corona is separated from the photosphere by the relatively shallow chromosphere. The exact mechanism by which the corona is heated is still the subject of some debate, the outer edges of the Suns corona are constantly being transported away due to open magnetic flux and hence generating the solar wind. The corona is not always evenly distributed across the surface of the sun, during periods of quiet, the corona is more or less confined to the equatorial regions, with coronal holes covering the polar regions. However, during the Suns active periods, the corona is evenly distributed over the equatorial and polar regions, the solar cycle spans approximately 11 years, from solar minimum to the following minimum. Associated with sunspots are coronal loops, loops of magnetic flux, the magnetic flux pushes the hotter photosphere aside, exposing the cooler plasma below, thus creating the relatively dark sun spots. The astronomers usually distinguish several regions, as described below, active regions are ensembles of loop structures connecting points of opposite magnetic polarity in the photosphere, the so-called coronal loops. They generally distribute in two zones of activity, which are parallel to the solar equator, the average temperature is between two and four million kelvins, while the density goes from 109 to 1010 particle per cm3. If flares are very violent, they can also perturb the photosphere, on the contrary, quiescent prominences are large, cool dense structures which are observed as dark, snake-like Hα ribbons on the solar disc. Their temperature is about 5000–8000 K, and so they are considered as chromospheric features. In 2013, images from the High Resolution Coronal Imager revealed never-before-seen magnetic braids of plasma within the layers of these active regions
26.
Solar wind
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The solar wind is a stream of charged particles released from the upper atmosphere of the Sun. This plasma consists of electrons, protons and alpha particles with thermal energies between 1.5 and 10 keV. Embedded within the plasma is the interplanetary magnetic field. The solar wind varies in density, temperature and speed over time and its particles can escape the Suns gravity because of their high energy resulting from the high temperature of the corona, which in turn is a result of the coronal magnetic field. At a distance of more than a few radii from the sun. The flow of the wind is no longer supersonic at the termination shock. The Voyager 2 spacecraft crossed the shock more than five times between 30 August and 10 December 2007, Voyager 2 crossed the shock about a billion kilometers closer to the Sun than the 13.5 billion kilometer distance where Voyager 1 came upon the termination shock. The spacecraft moved outward through the shock into the heliosheath. Other related phenomena include the aurora, the tails of comets that always point away from the Sun. The existence of flowing outward from the Sun to the Earth was first suggested by British astronomer Richard C. In 1859, Carrington and Richard Hodgson independently made the first observation of what would later be called a solar flare, george FitzGerald later suggested that matter was being regularly accelerated away from the Sun and was reaching the Earth after several days. In 1910 British astrophysicist Arthur Eddington essentially suggested the existence of the wind, without naming it. The idea never caught on even though Eddington had also made a similar suggestion at a Royal Institution address the previous year. In the latter case, he postulated that the material consisted of electrons while in his study of Comet Morehouse he supposed them to be ions. The first person to suggest that the material consisted of both ions and electrons was Kristian Birkeland. His geomagnetic surveys showed that activity was nearly uninterrupted. In 1916, Birkeland proposed that, From a physical point of view it is most probable that solar rays are neither exclusively negative nor positive rays, in other words, the solar wind consists of both negative electrons and positive ions. Three years later in 1919, Frederick Lindemann also suggested that particles of both polarities, protons as well as electrons, come from the Sun
27.
In situ
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In situ is a Latin phrase that translates literally to on site or in position. It means locally, on site, on the premises or in place to describe an event where it takes place, in the aerospace industry, equipment on-board aircraft must be tested in situ, or in place, to confirm everything functions properly as a system. Individually, each piece may work but interference from nearby equipment may create unanticipated problems, special test equipment is available for this in situ testing. In archaeology, in situ refers to an artifact that has not been moved from its place of deposition. In other words, it is stationary, meaning still, an artifact being in situ is critical to the interpretation of that artifact and, consequently, of the culture which formed it. Once an artifacts find-site has been recorded, the artifact can then be moved for conservation, further interpretation, an artifact that is not discovered in situ is considered out of context and as not providing an accurate picture of the associated culture. However, the out of context artifact can provide scientists with an example of types, when excavating a burial site or surface deposit in situ refers to cataloging, recording, mapping, photographing human remains in the position they are discovered. The label in situ indicates only that the object has not been newly moved. Thus, an archaeological in situ find may be an object that was looted from another place, an item of booty of a past war. Consequently, the in situ find site may not reveal its provenance. It is also possible for archaeological layers to be reworked on purpose or by accident, for example, in a Tell mound, where layers are not typically uniform or horizontal, or in land cleared or tilled for farming. The term in situ is used to describe ancient sculpture that was carved in place such as the Sphinx or Petra. This distinguishes it from statues that were carved and moved like the Colossi of Memnon, which was moved in ancient times. In art, in situ refers to a work of art made specifically for a host site, for a more detailed account see, Site-specific art. The term can refer to a work of art created at the site where it is to be displayed, rather than one created in the artists studio. In architectural sculpture the term is employed to describe sculpture that is carved on a building, frequently from scaffolds. A fraction of the star clusters in our galaxy, as well as those in other massive galaxies. The rest might have been accreted from now defunct dwarf galaxies, in biology and biomedical engineering, in situ means to examine the phenomenon exactly in place where it occurs
28.
Helioseismology
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Helioseismology is the process of inferring the internal structure and kinematics of the Sun from the propagation of seismic waves, particularly acoustic waves and surface gravity waves. It was developed by analogy to geoseismology, and subsequently there emerged asteroseismology, because the Sun is fluid, to a first approximation it cannot support shear waves, unlike the seismic waves on Earth. An exception is the waves which appear to be important only in the atmosphere. The helioseismic waves are generated by the turbulence in the zone immediately beneath the Suns surface. Certain frequencies are amplified by constructive interference, leading to resonance, in other words, the turbulence rings the sun like a bell. The resonant waves are reflected near the photosphere, the surface of the sun. The oscillations are detectable in almost any time series of solar images and that has permitted the evaluation of the quadrupole moment, J2 =1.8 ×10 −7, and higher-order moments of the Suns external gravitational potential. It is an accurate and more robust procedure than trying to infer it from the oblateness of the visible disc. Together with measurements of the orbits of Mercury and of spacecraft, helioseismology has been able to rule out the possibility that the solar neutrino problem was a result of incorrect static models of the interior of the Sun. Broadly speaking, the velocity of the convection zone decreases from equator to the poles, varying only weakly with depth. These two regions are separated by a layer called the tachocline, which is too thin to be resolved directly by seismological analysis alone. The convective zone has jet streams of plasma thousands of kilometers below the surface, the jet streams form broad fronts at the equator, breaking into smaller cyclonic storms at high latitudes. Torsional oscillations are the variation in solar differential rotation. They are alternating bands of faster and slower rotation, helioseismology can also be used to image the far side of the Sun from the Earth, including sunspots. In simple terms, sunspots both absorb and deflect helioseismic waves, causing a seismic deficit where next they encounter the photosphere, individual oscillations in the Sun are damped, in the absence of continual excitation they would die out in a few days. Resonating interference between propagating waves produces global standing waves, known also as normal modes, analysis of these modes constitutes the discipline of global helioseismology. G modes are standing internal gravity waves whose principal restoring force is negative buoyancy of vertically displaced material and they are of relatively low frequency. They are confined either to the interior of the sun below the convection zone, because they cannot propagate through convectively unstable regions, the former are practically unobservable at the surface
29.
Centripetal force
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A centripetal force is a force that makes a body follow a curved path. Its direction is orthogonal to the motion of the body. Isaac Newton described it as a force by which bodies are drawn or impelled, or in any way tend, in Newtonian mechanics, gravity provides the centripetal force responsible for astronomical orbits. One common example involving centripetal force is the case in which a body moves with uniform speed along a circular path, the centripetal force is directed at right angles to the motion and also along the radius towards the centre of the circular path. The mathematical description was derived in 1659 by the Dutch physicist Christiaan Huygens, the direction of the force is toward the center of the circle in which the object is moving, or the osculating circle. The speed in the formula is squared, so twice the speed needs four times the force, the inverse relationship with the radius of curvature shows that half the radial distance requires twice the force. Expressed using the orbital period T for one revolution of the circle, the rope example is an example involving a pull force. The centripetal force can also be supplied as a push force, newtons idea of a centripetal force corresponds to what is nowadays referred to as a central force. Another example of centripetal force arises in the helix that is traced out when a particle moves in a uniform magnetic field in the absence of other external forces. In this case, the force is the centripetal force that acts towards the helix axis. Below are three examples of increasing complexity, with derivations of the formulas governing velocity and acceleration, uniform circular motion refers to the case of constant rate of rotation. Here are two approaches to describing this case, assume uniform circular motion, which requires three things. The object moves only on a circle, the radius of the circle r does not change in time. The object moves with constant angular velocity ω around the circle, therefore, θ = ω t where t is time. Now find the velocity v and acceleration a of the motion by taking derivatives of position with respect to time, consequently, a = − ω2 r. negative shows that the acceleration is pointed towards the center of the circle, hence it is called centripetal. While objects naturally follow a path, this centripetal acceleration describes the circular motion path caused by a centripetal force. The image at right shows the relationships for uniform circular motion. In this subsection, dθ/dt is assumed constant, independent of time, consequently, d r d t = lim Δ t →0 r − r Δ t = d ℓ d t
30.
Lissajous orbit
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Lyapunov orbits around a Lagrangian point are curved paths that lie entirely in the plane of the two primary bodies. In contrast, Lissajous orbits include components in this plane and perpendicular to it, halo orbits also include components perpendicular to the plane, but they are periodic, while Lissajous orbits are not. In practice, any orbits around Lagrangian points L1, L2, or L3 are dynamically unstable, as a result, spacecraft in these Lagrangian point orbits must use their propulsion systems to perform orbital station-keeping. These orbits can however be destabilized by other nearby massive objects, several missions have used Lissajous orbits, ACE at Sun–Earth L1, SOHO at Sun-Earth L1, DSCOVR at Sun–Earth L1, WMAP at Sun–Earth L2, and also the Genesis mission collecting solar particles at L1. On 14 May 2009, the European Space Agency launched into space the Herschel and Planck observatories, eSAs current Gaia mission also uses a Lissajous orbit at Sun–Earth L2. In 2011, NASA transferred two of its THEMIS spacecraft from Earth orbit to Lunar orbit by way of Earth-Moon L1 and L2 Lissajous orbits. In the 2005 science fiction novel Sunstorm by Arthur C. Clarke and Stephen Baxter, the shield is described to have been in a Lissajous orbit at L1. In the story a group of wealthy and powerful people shelter opposite the shield at L2 so as to be protected from the storm by the shield, the Earth. Koon, W. S. M. W. Lo, J. E. Marsden, dynamical Systems, the Three-Body Problem, and Space Mission Design
31.
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
32.
Coronal mass ejection
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A coronal mass ejection is an unusually large release of plasma and magnetic field from the solar corona. They often follow solar flares and are present during a solar prominence eruption. The plasma is released into the wind, and can be observed in coronagraph imagery. Coronal mass ejections are associated with other forms of solar activity. CMEs most often originate from active regions on the Suns surface, near solar maxima, the Sun produces about three CMEs every day, whereas near solar minima, there is about one CME every five days. Coronal mass ejections release huge quantities of matter and electromagnetic radiation into space above the Suns surface, either near the corona, or farther into the planetary system, the ejected material is a plasma consisting primarily of electrons and protons. While solar flares are very fast, CMEs are relatively slow, Coronal mass ejections are associated with enormous changes and disturbances in the coronal magnetic field. They are usually observed with a white-light coronagraph, recent scientific research has shown that the phenomenon of magnetic reconnection is closely associated with CMEs and solar flares. In magnetohydrodynamic theory, the rearrangement of magnetic field lines when two oppositely directed magnetic fields are brought together is called magnetic reconnection. Reconnection releases energy stored in the original stressed magnetic fields and these magnetic field lines can become twisted in a helical structure, with a right-hand twist or a left hand twist. On the Sun, magnetic reconnection may happen on solar arcades—a series of closely occurring loops of magnetic lines of force and these lines of force quickly reconnect into a low arcade of loops, leaving a helix of magnetic field unconnected to the rest of the arcade. The sudden release of energy during this process causes the solar flare, the helical magnetic field and the material that it contains may violently expand outwards forming a CME. This also explains why CMEs and solar flares erupt from what are known as the active regions on the Sun where magnetic fields are much stronger on average. When the magnetosphere reconnects on the nightside, it releases power on the order of terawatt scale, Solar energetic particles can cause particularly strong aurorae in large regions around Earths magnetic poles. These are also known as the Northern Lights in the hemisphere. Energetic protons released by a CME can cause an increase in the number of electrons in the ionosphere. The increase in free electrons can enhance radio wave absorption, especially within the D-region of the ionosphere, humans at high altitudes, as in airplanes or space stations, risk exposure to relatively intense cosmic rays. A typical coronal mass ejection may have any or all of three features, a cavity of low electron density, a dense core, and a bright leading edge
33.
Electrical grid
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An electrical grid is an interconnected network for delivering electricity from suppliers to consumers. Power stations may be located near a source, at a dam site, or to take advantage of renewable energy sources. They are usually large to take advantage of the economies of scale. The electric power which is generated is stepped up to a voltage at which it connects to the electric power transmission network. The bulk power transmission network will move the power long distances, sometimes across international boundaries, on arrival at a substation, the power will be stepped down from a transmission level voltage to a distribution level voltage. As it exits the substation, it enters the distribution wiring, finally, upon arrival at the service location, the power is stepped down again from the distribution voltage to the required service voltage. Electrical grids vary in size covering an single building through national grids which cover whole countries. Early electric energy was produced near the device or service requiring that energy, in the 1880s, electricity competed with steam, hydraulics, and especially coal gas. Coal gas was first produced on premises but later evolved into gasification plants that enjoyed economies of scale. In the industrialized world, cities had networks of piped gas, but gas lamps produced poor light, wasted heat, made rooms hot and smoky, and gave off hydrogen and carbon monoxide. In the 1880s electric lighting soon became advantageous compared to gas lighting, Electric utility companies took advantage of economies of scale and moved to centralized power generation, distribution, and system management. With long distance power transmission it became possible to interconnect stations to balance load, merz was appointed head of a Parliamentary Committee and his findings led to the Williamson Report of 1918, which in turn created the Electricity Supply Bill of 1919. The bill was the first step towards an integrated electricity system, the Electricity Act of 1926 led to the setting up of the National Grid. The Central Electricity Board standardized the nations electricity supply and established the first synchronized AC grid and this started operating as a national system, the National Grid, in 1938. In the United States in the 1920s, utilities formed joint-operations to share peak load coverage, no longer were electric utilities built as vertical monopolies, where generation, transmission and distribution were handled by a single company. Now, the three stages could be split among various companies, in an effort to provide accessibility to high voltage transmission. The Energy Policy Act of 2005 allowed incentives and loan guarantees for energy production. In France, electrification began in the 1900s, with 700 communes in 1919, and 36,528 in 1938
34.
Satellite
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In the context of spaceflight, a satellite is an artificial object which has been intentionally placed into orbit. Such objects are called artificial satellites to distinguish them from natural satellites such as Earths Moon. In 1957 the Soviet Union launched the worlds first artificial satellite, since then, about 6,600 satellites from more than 40 countries have been launched. According to a 2013 estimate,3,600 remained in orbit, of those, about 1,000 were operational, the rest have lived out their useful lives and become space debris. Approximately 500 operational satellites are in orbit,50 are in medium-Earth orbit. A few large satellites have been launched in parts and assembled in orbit. Over a dozen space probes have been placed into orbit around other bodies and become artificial satellites to the Moon, Mercury, Venus, Mars, Jupiter, Saturn, a few asteroids, Satellites are used for many purposes. Common types include military and civilian Earth observation satellites, communications satellites, navigation satellites, weather satellites, Space stations and human spacecraft in orbit are also satellites. Satellite orbits vary greatly, depending on the purpose of the satellite, well-known classes include low Earth orbit, polar orbit, and geostationary orbit. A launch vehicle is a rocket that throws a satellite into orbit, usually it lifts off from a launch pad on land. Some are launched at sea from a submarine or a mobile maritime platform, Satellites are usually semi-independent computer-controlled systems. Satellite subsystems attend many tasks, such as power generation, thermal control, telemetry, attitude control, the first fictional depiction of a satellite being launched into orbit was a short story by Edward Everett Hale, The Brick Moon. The idea surfaced again in Jules Vernes The Begums Fortune, in 1903, Konstantin Tsiolkovsky published Exploring Space Using Jet Propulsion Devices, which is the first academic treatise on the use of rocketry to launch spacecraft. He calculated the speed required for a minimal orbit. In 1928, Herman Potočnik published his book, The Problem of Space Travel — The Rocket Motor. He described the use of orbiting spacecraft for observation of the ground, in a 1945 Wireless World article, the English science fiction writer Arthur C. Clarke described in detail the possible use of communications satellites for mass communications. He suggested that three geostationary satellites would provide coverage over the entire planet, the first artificial satellite was Sputnik 1, launched by the Soviet Union on October 4,1957, and initiating the Soviet Sputnik program, with Sergei Korolev as chief designer. This in turn triggered the Space Race between the Soviet Union and the United States, Sputnik 1 helped to identify the density of high atmospheric layers through measurement of its orbital change and provided data on radio-signal distribution in the ionosphere
35.
Geomagnetic storm
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A geomagnetic storm is a temporary disturbance of the Earths magnetosphere caused by a solar wind shock wave and/or cloud of magnetic field that interacts with the Earths magnetic field. The increase in the wind pressure initially compresses the magnetosphere. The solar winds magnetic field interacts with the Earth’s magnetic field, both interactions cause an increase in plasma movement through the magnetosphere and an increase in electric current in the magnetosphere and ionosphere. During the main phase of a storm, electric current in the magnetosphere creates a magnetic force that pushes out the boundary between the magnetosphere and the solar wind. The frequency of geomagnetic storms increases and decreases with the sunspot cycle, CME driven storms are more common during the maximum of the solar cycle, while CIR driven storms are more common during the minimum of the solar cycle. Several space weather phenomena tend to be associated with or are caused by a geomagnetic storm, in 1989, a geomagnetic storm energized ground induced currents that disrupted electric power distribution throughout most of the province of Quebec and caused aurorae as far south as Texas. In 1931, Sydney Chapman and Vincenzo C. A. Ferraro wrote an article, A New Theory of Magnetic Storms and they argued that whenever the Sun emits a solar flare it also emits a plasma cloud, now known as a coronal mass ejection. This plasma will travel at a velocity such that it reaches Earth within 113 days, the cloud then compresses the Earths magnetic field and thus increases this field at the Earths surface. A geomagnetic storm is defined by changes in the Dst index, the Dst index estimates the globally averaged change of the horizontal component of the Earth’s magnetic field at the magnetic equator based on measurements from a few magnetometer stations. Dst is computed once per hour and reported in near-real-time, during quiet times, Dst is between +20 and −20 nano-Tesla. A geomagnetic storm has three phases, initial, main and recovery, the initial phase is characterized by Dst increasing by 20 to 50 nT in tens of minutes. The initial phase is referred to as a storm sudden commencement. However, not all geomagnetic storms have a phase and not all sudden increases in Dst or SYM-H are followed by a geomagnetic storm. The main phase of a storm is defined by Dst decreasing to less than −50 nT. The selection of −50 nT to define a storm is somewhat arbitrary, the minimum value during a storm will be between -50 and approximately -600 nT. The duration of the phase is typically 2–8 hours. The recovery phase is when Dst changes from its value to its quiet time value. The recovery phase may last as short as 8 hours or as long as 7 days, the size of a geomagnetic storm is classified as moderate, intense or super-storm
36.
Geomagnetically induced current
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Geomagnetically induced currents, affecting the normal operation of long electrical conductor systems, are a manifestation at ground level of space weather. During space weather events, electric currents in the magnetosphere and ionosphere experience large variations and these variations induce currents in conductors operated on the surface of Earth. Electric transmission grids and buried pipelines are examples of such conductor systems. GIC can cause problems, such as increased corrosion of pipeline steel, GIC are one possible consequence of geomagnetic storms, which may also affect geophysical exploration surveys and oil and gas drilling operations. The Earths magnetic field varies over a range of timescales. The longer-term variations, typically occurring over decades to millennia, are predominantly the result of action in the Earths core. Geomagnetic variations on timescales of seconds to years also occur, due to processes in the ionosphere, magnetosphere and heliosphere. These changes are ultimately tied to variations associated with the activity cycle and are manifestations of space weather. The fact that the field does respond to solar conditions can be useful, for example, in investigating Earth structure using magnetotellurics. This geomagnetic hazard is primarily a risk to technology under the Earths protective atmospheric blanket, a time-varying magnetic field external to the Earth induces telluric currents—electric currents in the conducting ground. These currents create a magnetic field. As a consequence of Faradays law of induction, a field at the surface of the Earth is induced associated with time variations of the magnetic field. The surface electric field causes electrical currents, known as geomagnetically induced currents, to flow in any conducting structure, for example and this electric field, measured in V/km, acts as a voltage source across networks. GIC are often described as being quasi direct current, although the frequency of GIC is governed by the time variation of the electric field. For GIC to be a hazard to technology, the current has to be of a magnitude, the size of the GIC in any network is governed by the electrical properties and the topology of the network. The largest magnetospheric-ionospheric current variations, resulting in the largest external magnetic field variations, occur during geomagnetic storms, significant variation periods are typically from seconds to about an hour, so the induction process involves the upper mantle and lithosphere. GIC of tens to hundreds of amperes have been recorded, GIC have also been recorded at mid-latitudes during major storms. There may even be a risk to low areas, especially during a storm commencing suddenly because of the high
37.
Cartesian coordinate system
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Each reference line is called a coordinate axis or just axis of the system, and the point where they meet is its origin, usually at ordered pair. The coordinates can also be defined as the positions of the projections of the point onto the two axis, expressed as signed distances from the origin. One can use the principle to specify the position of any point in three-dimensional space by three Cartesian coordinates, its signed distances to three mutually perpendicular planes. In general, n Cartesian coordinates specify the point in an n-dimensional Euclidean space for any dimension n and these coordinates are equal, up to sign, to distances from the point to n mutually perpendicular hyperplanes. The invention of Cartesian coordinates in the 17th century by René Descartes revolutionized mathematics by providing the first systematic link between Euclidean geometry and algebra. Using the Cartesian coordinate system, geometric shapes can be described by Cartesian equations, algebraic equations involving the coordinates of the points lying on the shape. For example, a circle of radius 2, centered at the origin of the plane, a familiar example is the concept of the graph of a function. Cartesian coordinates are also tools for most applied disciplines that deal with geometry, including astronomy, physics, engineering. They are the most common system used in computer graphics, computer-aided geometric design. Nicole Oresme, a French cleric and friend of the Dauphin of the 14th Century, used similar to Cartesian coordinates well before the time of Descartes. The adjective Cartesian refers to the French mathematician and philosopher René Descartes who published this idea in 1637 and it was independently discovered by Pierre de Fermat, who also worked in three dimensions, although Fermat did not publish the discovery. Both authors used a single axis in their treatments and have a length measured in reference to this axis. The concept of using a pair of axes was introduced later, after Descartes La Géométrie was translated into Latin in 1649 by Frans van Schooten and these commentators introduced several concepts while trying to clarify the ideas contained in Descartes work. Many other coordinate systems have developed since Descartes, such as the polar coordinates for the plane. The development of the Cartesian coordinate system would play a role in the development of the Calculus by Isaac Newton. The two-coordinate description of the plane was later generalized into the concept of vector spaces. Choosing a Cartesian coordinate system for a one-dimensional space – that is, for a straight line—involves choosing a point O of the line, a unit of length, and an orientation for the line. An orientation chooses which of the two half-lines determined by O is the positive, and which is negative, we say that the line is oriented from the negative half towards the positive half
38.
Stepper motor
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A stepper motor or step motor or stepping motor is a brushless DC electric motor that divides a full rotation into a number of equal steps. Switched reluctance motors are very large stepping motors with a reduced pole count, DC brushed motors rotate continuously when DC voltage is applied to their terminals. The stepper motor is known by its property to convert a train of pulses into a precisely defined increment in the shaft position. Each pulse moves the shaft through a fixed angle, stepper motors effectively have multiple toothed electromagnets arranged around a central gear-shaped piece of iron. The electromagnets are energized by a driver circuit or a micro controller. To make the motor shaft turn, first, one electromagnet is given power, when the gears teeth are aligned to the first electromagnet, they are slightly offset from the next electromagnet. This means that when the electromagnet is turned on and the first is turned off. From there the process is repeated, each of those rotations is called a step, with an integer number of steps making a full rotation. In that way, the motor can be turned by a precise angle, there are two basic winding arrangements for the electromagnetic coils in a two phase stepper motor, bipolar and unipolar. An unipolar stepper motor has one winding with center tap per phase, each section of windings is switched on for each direction of magnetic field. Since in this arrangement a magnetic pole can be reversed without switching the direction of current, typically, given a phase, the center tap of each winding is made common, giving three leads per phase and six leads for a typical two phase motor. Often, these two phase commons are internally joined, so the motor has only five leads, a quick way to determine if the stepper motor is working is to short circuit every two pairs and try turning the shaft. Whenever a higher than normal resistance is felt, it indicates that the circuit to the winding is closed. Bipolar motors have a single winding per phase, the current in a winding needs to be reversed in order to reverse a magnetic pole, so the driving circuit must be more complicated, typically with an H-bridge arrangement. There are two leads per phase, none are common, static friction effects using an H-bridge have been observed with certain drive topologies. Dithering the stepper signal at a higher frequency than the motor can respond to will reduce this static friction effect, because windings are better utilized, they are more powerful than a unipolar motor of the same weight. This is due to the space occupied by the windings. A unipolar motor has twice the amount of wire in the same space, though a bipolar stepper motor is more complicated to drive, the abundance of driver chips means this is much less difficult to achieve
39.
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
40.
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
41.
Arecibo Observatory
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The Arecibo Observatory is a radio telescope in the municipality of Arecibo, Puerto Rico. This observatory is operated by SRI International, USRA and UMET, the observatory is the sole facility of the National Astronomy and Ionosphere Center, which refers to the observatory, and the staff that operates it. From its construction in the 1960s until 2011, the observatory was managed by Cornell University and it is used in three major areas of research, radio astronomy, atmospheric science, and radar astronomy. Scientists who want to use the observatory submit proposals that are evaluated by an independent scientific board, the observatory has appeared in film and television productions, gaining more recognition in 1999 when it began to collect data for the SETI@home project. It has been listed on the American National Register of Historic Places starting in 2008 and it was the featured listing in the National Park Services weekly list of October 3,2008. The center was named an IEEE Milestone in 2001 and it has a visitor center that is open part-time. The main collecting dish is 305 m in diameter, constructed inside the left by a karst sinkhole. The dish surface is made of 38,778 perforated aluminum panels, each about 3 by 6 feet, the ground beneath is accessible and supports shade-tolerant vegetation. The observatory has four transmitters, with effective isotropic radiated powers of 20 TW at 2380 MHz,2.5 TW at 430 MHz,300 MW at 47 MHz. The reflector is a reflector, not a parabolic reflector. To aim the device, the receiver is moved to intercept signals reflected from different directions by the dish surface of 270 m radius. A parabolic mirror would have varying astigmatism when the receiver is off the focal point, the platform has a rotating, bow-shaped track 93 m long, called the azimuth arm, carrying the receiving antennas and secondary and tertiary reflectors. This allows the telescope to observe any region of the sky in a cone of visibility about the local zenith. Puerto Ricos location near the Northern Tropic allows Arecibo to view the planets in the Solar System over the Northern half of their orbit. The round trip time to objects beyond Saturn is longer than the 2.6 hour time that the telescope can track a celestial position. The origins of the trace to late 1950s efforts to develop anti-ballistic missile defences as part of the newly formed ARPAs ABM umbrella-effort. Even at this stage it was clear that the use of radar decoys would be a serious problem at the long ranges needed to successfully attack a warhead. Among the many Defender projects were several studies based on the concept that a nuclear warhead would cause unique physical signatures while still in the upper atmosphere
. doi:10.2514/1.11950.
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